High Fidelity Simulation of Low Velocity Impact Behavior of CFRP Laminate Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-18 Masaya Ebina, Akinori Yoshimura, Kenichi Sakaue, Anthony M. Waas
In this paper, a finite element (FE) model which simulates damage extent of CFRP laminate subjected to low velocity face-on impact is proposed. The validity of the model is demonstrated by comparing experimental and numerical results for two different CFRPs with different stacking sequence and boundary conditions. Experimental damage extent were obtained from the drop-weight test and non-destructive inspections (C-scan, radiograph and X-ray CT). Numerical results were obtained from FE analyses done on Abaqus/Explicit 2016. In the present model, each damage mode is modeled separately. Fiber damage is modeled by smeared crack model (SCM). In-plane ply cracks are modeled by the enhanced continuum damage mechanics (ECDM) model, which is composed of continuum damage mechanics (CDM) and SCM. Delamination between laminae is modeled by cohesive behavior based on the contact formulation. For both CFRPs, numerical results obtained from the present model show reasonable agreement with experimental results.
Research on High Electromagnetic Interference Shielding Effectiveness of a Foldable Buckypaper/Polyacrylonitrile Composite Film via Interface Reinforcing Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-17 Qianshan Xia, Zhichun Zhang, Hetao Chu, Yanju Liu, Jinsong Leng
Herein, a series of foldable buckypaper/polyacrylonitrile (BP/PAN) composite films were developed in a facile strategy. This strategy was based on electrospun and vacuum pressurized filtration methods. The composite film had better mechanical properties than pristine BP via interface reinforcing, but not deprived of excellent conductivity. The maximum tensile strength and elongation at break of BP/PAN films were 1.45 and 11.65 times than pristine BP, respectively. Moreover, BP/PAN film had higher electromagnetic interference (EMI) shielding effectiveness (63.7-65 dB) in the Ku band (12-18 GHz) than pristine BP (34.3-42.9 dB), due to interfaces forming between PAN fibers and CNTs. The BP/PAN composite as a promising EMI shielding material could be utilized in military and civil applications, such as flexible antenna, EMI shielding clothes and soft portable electronic products.
Strain and Damage Self-Sensing of Basalt Fiber Reinforced Polymer Laminates Fabricated with Carbon Nanofibers/Epoxy Composites under Tension Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-17 Yanlei Wang, Yongshuai Wang, Baolin Wan, Baoguo Han, Gaochuang Cai, Ruijuan Chang
This study investigated the strain and damage self-sensing capabilities of basalt fiber reinforced polymer (BFRP) laminates fabricated with carbon nanofibers (CNFs)/epoxy composites subjected to tensile loadings. The conduction mechanisms based on the tunnel conduction and percolation conduction theories as well as the damage evolution were also explored. A compensation circuit with a half-bridge configuration was proposed. The results indicated the resistivity of the CNFs/BFRP laminates and CNFs/epoxy composites exhibited similar change rule, indicating that the conductive networks of CNFs/BFRP laminates were governed by CNFs/epoxy composites. With the increase of strain under monotonic tensile loading, the electrical resistance response could be classified into three stages corresponding to different damage modes. This confirmed CNFs/BFRP laminates have excellent self-sensing abilities to monitor their internal damages. Moreover, stable and repeatable strain self-sensing capacity of the CNFs/BFRP laminates was verified under cyclic tensile loading because the electrical resistance varied synchronously with the applied strain.
The Double Drum Peel (DDP) test: a new concept to evaluate the delamination fracture toughness of cylindrical laminates Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-17 F. Daghia, C. Cluzel, L. Hébrard, F. Churlaud, B. Courtemanche
Standard delamination tests of monolithic composites prescribe configurations where the crack is a symmetry plane for both overall geometry and stacking sequence, ensuring a controlled mode ratio. These normalized configurations do not enable testing of curved specimens, like those manufactured by filament winding. Here, we propose a new concept for the delamination testing of cylindrical laminates, the Double Drum Peel , related to the peel tests used for adhesives or thin-films debonding. A global energy analysis, including all sources of energy release and dissipation, provides the expression of the critical strain energy release rate. As in the classical peel test, the energy dissipated by mechanisms other than delamination should be accounted for to determine intrinsic interface properties. The local mode mixity is evaluated based on analytical results on the classical peel test. Tests using carbon-peek rings manufactured by laser assisted tape placement are presented to illustrate the potential of the DDP.
Mechanical, thermal and flame retardant properties of magnesium hydroxide filled poly(vinyl chloride) composites: The effect of filler shape Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-10 Yunhua Lu, Chifei Wu, Shiai Xu
Magnesium hydroxide particle (MHP) and magnesium hydroxide whisker (MHW) were surface modified with a newly-synthesized polyether titanate coupling agent (eTi4000), and then incorporated into poly(vinyl chloride) (PVC) by melt blending to prepare PVC composites. The effect of filler shape on the mechanical, thermal and flame retardant properties of the resultant PVC composites was investigated. In general, MHP/PVC composites have better mechanical, thermal and flame retardant properties than MHW/PVC composites. The flexural modulus and impact strength of eTi4000 modified MHP (eTi4000-MHP)/PVC composites are 5740 MPa and 8.3 kJ m-2 at a 10 wt.% filler loading, with an increase of 217% and 48.2% compared with that of MHP/PVC composites, respectively. Significantly, eTi4000-MHP/PVC composites show good flame retardancy, and the incorporation of 30 wt.% of eTi4000-MHP results in 66.9% and 88.1% reduction of the total heat release and smoke production compared with that of pure PVC, respectively.
Multi-scale modeling of the viscoelastic behavior of 3D woven composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-11 Martin Hirsekorn, Lionel Marcin, Thierry Godon
A method is presented to predict numerically the homogenized viscoelastic behavior of 3D woven composites using only its constituents’ behavior. It is based on elastic homogenizations applied to the Laplace-Carson transform of the time-dependent viscoelastic behavior of the constituents. Two scale chages are necessary: from micro- to meso-scale to obtain the homogenized behavior of the consolidated yarns, and from meso- to macro-scale. The temperature and cure dependent viscoelastic behavior of the matrix is identified from experimental data, using the time-temperature superposition principle with the cure dependent glass transition temperature as reference temperature. The meso-scale representative unit cell of the composite is extracted from X-ray microtomography images. The homogenized viscoelastic behavior is used to calculate the evolution of the apparent moduli of the composite with temperature between - 50 ° C and 200 ° C. The results are in good agreement with experimental data over the temperature range where the matrix behavior was properly identified.
A 3D tomographic investigation to elucidate the low-velocity impact resistance, tolerance and damage sequence of thin non-crimp fabric laminates: effect of ply-thickness Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-11 S.M. García-Rodríguez, J. Costa, A. Bardera, V. Singery, D. Trias
While thin-plies delay the onset of matrix cracking and improve certain in-plane mechanical properties, the effect they have on the out-of-plane response remains unclear. We compared the impact resistance, tolerance and sequence of failure events of thin laminates manufactured with thin- or standard-ply non-crimp fabrics (fibre areal weight of 67 and 134 gsm per ply). Damage initiation and propagation was detailed using (a) quasi-static indentation and impact tests at incremental energy levels and (b) X-ray tomography. The analysis revealed the damage mechanisms underlying the observed load drops in the force-displacement curves. In the indented specimens, the 3D post-process ascribed matrix cracks and delaminations to their corresponding plies/interfaces. Standard-ply samples develop more extended delaminations and delay fibre failure, improving the load-carrying capacity and increasing compression after impact (CAI) strength by 27% for impact at 14 J.
Interfacial adhesion assessment in flax/epoxy and in flax/vinylester composites by single yarn fragmentation test: correlation with micro-CT analysis Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-11 M.C. Seghini, F. Touchard, F. Sarasini, L. Chocinski-Arnault, D. Mellier, J. Tirillò
Despite the academic interest in using plant fibres as reinforcement in polymer composites to replace glass fibres, the industrial exploitation of resulting composites in semi- or structural applications is still limited. This is mainly due to the poor adhesion at the plant fibre/polymer matrix interface dictated by their surface chemistry and strong hydrophilic behaviour. In the present work, an assessment of the interfacial adhesion at the yarn scale has been carried out. Fragmentation tests have been performed on flax/epoxy and flax/vinylester single yarn composites. High-resolution microtomography has allowed a 3-D reconstruction of the breaking area of the flax yarn. The flax/epoxy system has shown the lowest values of critical fragment length and interfacial debonding length, and the highest values of IFSS. For both epoxy and vinylester samples, it was found that the breakage of flax has been mainly concentrated in the peripheral zone of the yarn.
Deconsolidation of C/PEEK blanks: on the role of prepreg, blank manufacturing method and conditioning Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-05 T.K. Slange, L.L. Warnet, W.J.B. Grouve, R. Akkerman
The combination of rapid automated lay-up and stamp forming has great potential for rapid manufacturing of lightweight load carrying components of thermoplastic composites. However, deconsolidation during blank heating is currently limiting the applicability of rapid lay-up blanks. This experimental work investigates the origin of deconsolidation in blanks produced by advanced fiber placement (AFP) versus traditional press consolidation. The influence of moisture on deconsolidation is investigated through deconsolidation experiments in a convection oven, as well as thermo-mechanical and residual gas analyses. The experiments revealed that thermal expansion of dissolved moisture is the main deconsolidation mechanism for press-consolidated blanks, but not for AFP blanks, which are suggested to deconsolidate mainly due to the release of frozen-in fiber stresses present in the used prepreg.
Mechanical anisotropy of paper-based all-cellulose composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-05 Henri Kröling, Benoît Duchemin, Jan Dormanns, Samuel Schabel, Mark P. Staiger
The effects of fibre orientation and laminate stacking sequence on the mechanical anisotropy of paper-based all-cellulose composites produced via a partial dissolution route is examined. As part of this work, the fibre architecture and microstructure of the paper precursor is controlled and characterised in order to follow the anisotropy of the materials through from precursor to final composite material. The fibre orientation of the precursor was found to strongly influence the mechanical anisotropy of the final composite material. The ultimate tensile strength and Young’s modulus of the paper-based all-cellulose composite laminates was 191 MPa and 17.5 GPa in the fibre direction, respectively, compared with 104 MPa and 10.4 GPa in the transverse direction, respectively. The ACC crystal structure was assessed with powder and transmission mode Wide-angle X-ray diffraction (WAXD) to measure the changes in crystallinity and crystal orientation due to the dissolution process. The mechanical response of multi-axial all-cellulose composite laminates was also determined experimentally and compared with analytical predictions by Classical Lamination Theory, demonstrating the utility of CLT for the prediction of the elastic properties of ACC laminates.
Validation of carbon fibers recycling by pyro-gasification: the influence of oxidation conditions to obtain clean fibers and promote fiber/matrix adhesion in epoxy composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-06 Laura Mazzocchetti, Tiziana Benelli, Emanuele D'Angelo, Chiara Leonardi, Giorgio Zattini, Loris Giorgini
This work aims at demonstrating, at a pilot plant scale, the potential of the pyro-gasification process to produce carbon fibers (CF) as secondary raw materials. The solid residue obtained upon pyrolysis was characterized and oxidized, applying different process conditions to provide clean fibers. The same process was applied to virgin fibers, thus highlighting the protective action that char provides to CF during the oxidation step. The recovered fibers were used to produce new short fiber composites which, upon optimization of the mixing and curing conditions, were competitive with the performance of pristine fibers composites. Indeed, the oxidation leaves an oxygen rich surface which positively interacts with the epoxy resin, thus promoting adhesion without the requirement of an additional sizing process after the CFs recycling. These results provided sufficient validation of the recovered CF quality, thus leading to the scale up of the process to produce an integrated pyro-gasification semi—industrial plant.
Three dimensional hexagonal boron nitride nanosheet/carbon nanotube composites with light weight and enhanced microwave absorption performance Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-07 Bo Zhong, Yuanjing Cheng, Meng Wang, Yongqing Bai, Xiaoxiao Huang, Yuanlie Yu, Huatao Wang, Guangwu Wen
Three dimensional hexagonal boron nitride nanosheet decorated carbon nanotube composites (3D h-BNNS/CNTs) have been fabricated through a facile thermal treatment process. h-BNNSs randomly distribute among CNTs to form 3D network structure. The microwave absorption properties of these 3D h-BNNS/CNTs are obviously improved comparing with those of CNTs. And the maximum reflection loss (RL) can reach up to -36.5 dB when the absorber thickness is 2.5 mm for 3D h-BNNS/CNTs1 derived from the precursor with boric acid, urea and CNTs molar ratio of 2:4:1. Besides, the maximum absorption bandwidth (RL ≤ -10 dB) is as large as 4.0 GHz when the absorber thickness drops to 2.0 mm. More important, h-BNNS/CNTs1 has a low density of 112.6 ± 3.6 mg/cm3, which is beneficial for practical applications. The significant enhancement in MA performance of h-BNNS/CNTs is mainly attributed to the improvement of impedance matching, interfacial polarization and multiple scattering after introduction of h-BNNSs.
High wear-resistant performance of thermosetting polyimide reinforced by graphitic carbon nitride (g-C3N4) under high temperature Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-07 Chunjian Duan, Dongming Yuan, Zenghui Yang, Song Li, Liming Tao, Qihua Wang, Tingmei Wang
The two-dimensional (2D) material of graphitic carbon nitride (g-C3N4) has shown great promise for tribo-materials due to special molecular structure. In this work, we report an effective approach to enhance anti-wear of thermosetting polyimide (TPI) by filling with g-C3N4 under high temperature. TPI composite (TPT-1) and g-C3N4 were firstly prepared. Then, friction and wear behavior of TPT-1 was studied and comparatively evaluated with neat resin from room temperature to 350°C. As a result, the wear resistance of TPI was able to significantly improve and an much lower wear rate (7.29×10-7 mm3/N·m) was achieved at 350°C. Moreover, mechanism of friction and wear was demonstrated that transfer film formed by introducing g-C3N4 with high E-modulus and hardness could effectively share the load with TPI and prevent from further abrasion of resin in contact surfaces. This work could help researchers to design a new TPI tribo-material used at high temperature.
Excellent EMI Shielding performance and Thermal Insulating Properties in Lightweight, Multifunctional Carbon-Cenosphere Composite Foams Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-04 Rajeev Kumar, D.P. Mondal, Anisha Chaudhary, Muhamed Shafeeq, Saroj Kumari
Lightweight carbon foam has been considered as one of the most promising candidates for providing excellent EMI shielding performance in the fields of aerospace and portable electronics. Here, multifunctional lightweight carbon composite foams were developed by the impregnation of phenolic resin and cenospheres (0-40 wt. %) into polyurethane (PU) foam substrate. Subsequent impregnated foams were converted into carbon-cenosphere composite foams via heat treatment at 1000°C. The influence of cenosphere particles on the morphological, physical, mechanical electrical and thermal properties of carbon-cenosphere composite foams were studied in details. EMI shieling of carbon-cenosphere composite foam was measured in X-band frequency region (8.2-12.4 GHz) using waveguide method. The total shielding effectiveness (SE) of carbon foam was increased from -25.2 to -48.6 dB by the loading of 30 wt. % cenosphere. The thermal conductivity achieve as low as 0.02 W/(m.K), which is similar to aerogel.
Size limitations on achieving tough and healable fibre reinforced composites through the use of thermoplastic nanofibres Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-07-04 Amaël Cohades, Lode Daelemans, Charlie Ward, Timo Meireman, Wim Van Paepegem, Karen De Clerck, Véronique Michaud
Phase-separated blends of epoxy and poly(ε-caprolactone) (PCL) provide crack repair in composites after a thermal treatment at 150°C, but decrease the material's fracture toughness. This article investigates the combination of healing with interlaminar fracture toughness improvement using electrospun PCL nanofibrous veils, interleaved between glass fibre reinforcement layers. Cure temperature close to PCL melting leads to both phase-separated domains and intact nanofibre regions. With the fast cure kinetics of the epoxy resin, phase-separated domains consist of small epoxy particles (1-5 μm diameter) surrounded by a PCL matrix. Interlaminar crack propagation in Mode I demonstrates up to 48% toughness increase when 30 g/m2 of nanofibres are inserted between each layers. Thermal treatment however results in limited healing due to slow flow of PCL in the narrow channels. Further insight is provided regarding the channel width and polymer viscosity requirements to provide a microstructure efficient for both crack healing and interlaminar toughness improvement.
Damage EVOLUTION in UNIDIRECTIONAL AND CROSS-PLY flax/epoxy laminates SUBJECTED TO LOW VELOCITY IMPACT LOADING Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-30 Benedict Lawrence Sy, Zouheir Fawaz, Habiba Bougherara
With the resurgence of natural fibers as a viable alternative to synthetic fibers, there is a need to study their mechanical behaviour under different modes of loading. In this research, flax/epoxy composite laminates were manufactured and tested under low velocity impact loading to study the damage development on the laminates and assess their capability for low velocity impact applications. The laminates were tested using a pendulum-type impact apparatus. Two composite laminate configurations were tested: a symmetric unidirectional flax/epoxy laminate with stacking sequence 8S and a symmetric cross-ply flax/epoxy laminate with stacking sequence [0/90]4S. The unidirectional laminate exhibited poor and brittle behaviour under impact loading, with an energy penetration threshold of 10J and an impact toughness of 34 kJ/m2. On the other hand, the cross-ply laminate showed better impact performance, with its energy penetration threshold and impact toughness being three and 2.5 times higher than that of the unidirectional laminate, respectively.
Complementary analytical imaging techniques for the characterization of pretreated carbon fiber reinforced plastics ☆ Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-30 Stefan Viehbeck, Christian Iffelsberger, Frank-Michael Matysik
Effects of Intumescent Flame Retardant System Consisting of Tris (2-hydroxyethyl) Isocyanurate and Ammonium Polyphosphate on the Flame Retardant Properties of High-density Polyethylene Composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-25 Santosh Khanal, Weipeng Zhang, Saad Ahmed, Muhammad Ali, Shiai Xu
An intumescent flame retardant (IFR) system composed of tris (2-hydroxyethyl) isocyanurate (THEIC) and ammonium polyphosphate (APP) was used to prepare high density polyethylene (HDPE) composites, and their thermal and flammability properties were studied. The limiting oxygen index of the HDPE composite containing 30 wt. % of IFR with an APP: THEIC weight ratio of 3:1 (HD31) reaches 31.5 %. The cone calorimeter analysis shows that the peak and average heat release rate of HD31 are reduced by 69.5 % and 58.1 % respectively; while the average mass loss rate is reduced by 77.2 %. The thermogravimetric analysis suggests that the IFR/HDPE composites have good char forming ability. The structural analysis of the char residue shows that the intumescent char is composed of a polyaromatic structure containing nitrogen in five or six-membered ring linked to phospho-carbonaceous structure via the P-O-C linkage, and some phosphorous degradation products containing P-O-P structure.
Polyaniline: a novel bridge to reduce the fire hazards of epoxy composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-25 Keqing Zhou, Changkun Liu, Rui Gao
As a graphene-like two dimensional nanomaterial, MoS2 had been considered as promising nanofillers for fabrication of polymer-based materials with high performances. However, its dispersion and functionalization represented a critical challenge. In present work, polyaniline (PANI) coating was successfully grown on the surface of exfoliated MoS2 nanosheets by in situ polymerization method in order to improve the dispersion quality and interfacial interactions between MoS2 and polymer matrix. The obtained PANI-MoS2 hybrids were characterized through XRD, Raman spectrum, FTIR, TGA, XPS, TEM and further introduced into epoxy matrix. It was clearly observed that the addition of a PANI coating not only improved the dispersion of MoS2 in the matrix and the interfacial bonding between MoS2 and epoxy, but also obviously reduced the fire hazards of epoxy. By adding 2 wt % PANI-MoS2, the peak heat release rate and total heat release values of epoxy composites were remarkably reduced by 49% and 22%, respectively, in comparison with those of neat epoxy. In addition, the amount of smoke produced and toxic CO released was inhibited obviously. The well dispersion, labyrinth barrier effect, catalytic charring effect of PANI-MoS2 hybrids and combination effect between PANI and MoS2 were believed to the primary source for the remarkable improvement of fire safety.
Effect of Nanoscale Dispersed Silica on the Fabrication of Microporous Poly(L-lactic acid) by Uniaxial Stretching Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-25 Yunjing Chen, Lijing Han, Helong Chen, Shiling Jia, Lisong Dong
The microporous poly(L-lactic acid) (PLLA) was prepared successfully by uniaxial stretching PLLA with nanoscale dispersed silica as pore forming agent. The SEM results revealed that the silica dispersed uniformly in the PLLA matrix with the form of monodispersed nanoparticles or nanoscale aggregates when the content was 3 - 20 wt%. The number and size of the micropores and the porosity for the microporous PLLA were increased with the increase of silica content, stretching ratio and stretching rate (5 - 20 mm/min), while were reduced with the rise of stretching temperature. The stretching ratio of 2.5 was the key point for pore forming when silica content was under 10 wt%. The porosity was up to 21.1% with the silica content of 20 wt% and stretching ratio of 4.5. The mechanical properties and thermal insulation properties of microporous PLLA were also improved comparing with that of PLLA without pores.
Nanocellulose reinforced P(AAm-co-AAc) hydrogels with improved mechanical properties and biocompatibility Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-23 Shu Huang, Zhan Zhao, Chuang Feng, Edwin Mayes, Jie Yang
Carboxylate modified cellulose nanofibril (CNF) was used to reinforce poly(acrylamide-co-acrylic acid) (P(AAm-co-AAc)) hydrogel via in-situ polymerization. With introduction of Fe3+-carboxylate complexation, a dual cross-linking network structure in the P(AAm-co-AAc)/CNF hydrogels was constructed, i.e. the covalently cross-linked acrylic components forming a macromolecular network, and the noncovalently COO--Fe3+ ionic coordination bonds acting as secondary cross-linking points. The microstructure of the hydrogels was characterized by scanning electron microscopy (SEM). By incorporating 0.6 wt% CNF, the elastic modulus, tensile strength and toughness of P(AAm-co-AAc) hydrogel were improved by 240%, 104% and 51%, respectively. The addition of CNF also enhanced the energy dissipation in loading and unloading tests. P(AAm-co-AAc)/CNF nanocomposite hydrogels showed water content (70% to 80%) comparable with that in human cartilage (75%). The biocompatibility tests suggested that P(AAm-co-AAc)/CNF had no toxicity to cells and cells can adhere and proliferate well on the surface, making it suitable for biomedical and tissue engineering applications.
Mullite-zirconia-fibre/molybdenum-matrix composites: strength and damage tolerance Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-19 S.T. Mileiko, V.A. Chumichev
Molybdenum-matrix composites reinforced with composite fibres containing mullite and zirconia in various proportions (including that corresponding to eutectic) were successfully produced by the internal crystallisation method. The composites are characterised by a high damage tolerance: the average notch sensitivity value is 0.71, while the maximum value of this parameter approaches 1. Composites with eutectic and off-eutectic fibre compositions are sufficiently strong at temperatures up to 1400°C. The mean strength values are 178 MPa and 140 MPa at temperatures of 1300 and 1400°C, respectively.
Mullite-zirconia fibres produced by internal crystallization method: Microstructure and strength properties Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-19 S.T. Mileiko, A.A. Kolchin, N.I. Novokhatskaya, N.A. Prokopenko, O.F. Shakhlevich
Mullite-zirconia ceramics produced by powder metallurgy methods or directional solidification are well-known materials that combine the high creep resistance of mullite and the enhanced fracture toughness of a composite microstructure. These features provide a potential for the use of the material as a fibrous reinforcement for metal and ceramic matrices to obtain high-temperature fibrous composites. In this study, the microstructure and room- and high-temperature strength of mullite-ZrO2 fibres produced by the internal crystallisation method (ICM) were evaluated. The ICM provides a high productivity rate of fabrication technologies and, therefore, a potential to produce fibres suitable for structural applications. The room- and high-temperature strengths of the ICM fibres were comparable to those of the corresponding ceramics obtained by melt crystallization.
Carbon nanotubes reinforced reactive powder concrete Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-19 Yanfeng Ruan, Baoguo Han, Xun Yu, Wei Zhang, Danna Wang
In this paper, four types of multi-walled carbon nanotubes (MWCNTs) were incorporated into reactive powder concrete (RPC) with water or heat curing. The enhancing effects of MWCNT types and curing methods on mechanical properties of RPC were investigated. Experimental results indicate that adding proper type and content of MWCNTs can effectively improve mechanical properties of RPC including flexural strength, fracture energy, compressive strength/toughness and flexural strength to compressive strength ratio. In general, these mechanical properties of MWCNTs filled RPC with heat curing are superior to that with water curing, which indicates that heat curing is more beneficial for reinforcing impact of MWCNTs to RPC than water curing. In most cases, the critical length of MWCNTs in RPC is smaller than actual length, which indicates MWCNTs will be snapped when damage occurs in RPC. In addition, the reinforcement of MWCNTs to RPC results from crack bridging and pull out effects.
Improved wettability and interfacial adhesion in carbon fibre/epoxy composites via an aqueous epoxy sizing agent Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-20 Fuyao Liu, Zhuo Shi, Yubing Dong
In this paper, a modified epoxy emulsifier (MEE) was synthesised for preparing an aqueous epoxy sizing agent, which was used to reinforce interfacial adhesion of carbon fibre (CF)/epoxy composites. The sizing agent was evenly wrapped on the fibre surface with tiny particles, as well as increased the surface roughness of fibres; meanwhile, the activated carbon atoms on the surface of sized CF were further increased, as confirmed via SEM, AFM and XPS. The contact angle (CA) of fibres was observed via drop-on-fibre system. The results showed that the wettability of CF was significantly improved and the CA of CF was reduced by approximately 23°. According to the single-fibre fragmentation test, the interfacial shear strength of sized CF/EP composites increased by 70%–76%. The improvement of interfacial adhesion could be mainly attributed to the generation of chemical interaction bonds and the interface mechanical interlock of CF and the epoxy matrix.
Joining of carbon fiber reinforced thermoplastic and metal via friction stir welding with co-controlling shape and performance Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-20 Yongxian Huang, Xiangchen Meng, Yuming Xie, Junchen Li, Long Wan
Short carbon fiber reinforced poly-ether-ether-ketone (SCF/PEEK) and 2060-T8 aluminum alloy (AA2060-T8) were joined via friction stir welding with co-controlling shape and performance. The high-quality surface integrity and joint formation were acquired based on a tapered thread pin with the triple facets, a stationary shoulder and a new lap configuration of the SCF/PEEK and the AA2060-T8 at the upper and lower sides. An intimate contact formed at the AA2060-T8 and the SCF/PEEK interface. The macro/micro-mechanical interlocking and the chemical bond attributed to the main bonding mechanisms. Decreasing heat input was beneficial to eliminating the welding defects and improving the load bearing of the joint. The maximum tensile shear strength was 33 MPa. This work indicates that friction stir welding with co-controlling shape and performance has the feasible and potential to join thermoplastic and metal.
Physical properties of green composites based on poly-lactic acid or Mater-Bi® filled with Posidonia Oceanica leaves Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-19 Roberto Scaffaro, Andrea Maio, Francesco Lopresti
This work focuses on the evaluation of Posidonia Oceanica leaves as effective reinforcing agent for ecofriendly, fully biodegradable polymer composites. Posidonia leaves were washed, ground and sieved in order to achieve two different size distributions and aspect ratios. They were then added to either a stiff or a ductile biodegradable polymer matrix, respectively poly-lactic acid (PLA) and MaterBi® (MB), at two different filler contents (10 wt% and 20 wt%). The materials were fully characterized from a spectroscopic, morphological, rheological, and mechanical point of view. In particular, the outcomes of tensile tests were statistically analyzed by using a Full Factorial Design in order to examine the main effect of type of polymer, filler size and filler content (as well as their mutual interactions) on two properties of great concern, such as elastic modulus and toughness.
Combining interface damage and friction in cohesive interface models using an energy based approach Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-15 Zhenmin Zou, Marwah Hameed
Cohesive zone models coupling interface damage and friction have been developed in the literature and are available in the commercial finite element package ABAQUS to consider the enhancing effect of through-thickness compression on interfacial fracture resistance. It is revealed in this paper that these models are extremely dependent on interface stiffness, because interface stiffness reduction factor is used to combine damage and friction in these models. The interfacial constitutive law converges but only when the interface is extremely stiff and an unrealistic evolution of the interface damage is produced. A new approach is then developed which uses a cohesive energy related parameter to combine interface damage and friction. The behaviour of the new coupled model is independent of the interface stiffness once the interface is moderately stiff. The new and existing damage/friction coupled models have been employed to simulate the shear failure of a composite specimen and the predictions are compared against the experimental data in the literature. The new model produces converged results over a wide range of interface stiffness and the predictions match the experiments quite well, better than the existing models.
Characterizing and Modelling Delamination of Carbon-Fiber Epoxy Laminates during Abrasive Waterjet Cutting Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-15 J. Schwartzentruber, M. Papini, J.K. Spelt
Delamination is a common defect when abrasive waterjet (AWJ) cutting composite laminates. This paper presents experimental and numerical results used to characterize delamination when AWJ cutting a carbon-fiber/epoxy laminate. A fluid-structure interaction model was used to simulate the AWJ cutting. The structural domain used cohesive zone modeling to predict delamination along the ply interfaces. The numerical results showed that cutting delamination of the carbon-fiber/epoxy was primarily dependent on the normal interlaminar stress, with relatively large damage zones occurring ahead of the cutting front. This trend was also observed in x-ray micro-tomographs of an AWJ cut. To distinguish between side-wall and cutting-front forces, the loading generated by the jet was measured using a strain gage. This showed that the loads applied to the cutting front were larger than those generated on the side walls, and thus the likelihood of delamination was greater on the cutting front. The amount of delamination during AWJ cutting was measured using a moisture uptake methodology that was implemented with a six-factor (pressure, stand-off distance, abrasive flow rate, traverse speed, mixing-tube size, and fiber orientation) Taguchi experimental design. The trends evident in these data were consistent with the extent of delamination predicted by the numerical models, and show that traverse speed, abrasive flow rate, and mixing tube size had the most significant effect on delamination.
Influence of the nanoscaled hybrid based on nanodiamond@graphene oxide architecture on the rheological and thermo-physical performances of carboxylated-polymeric composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-15 Yinhang Zhang, Soo-Jin Park
A carbon/carbon hybrid nanofiller based on nanodiamond-decorated graphene oxide (ND@GO) was designed using 4,4’-methylene diphenyl diisocyanate as the coupling agent and incorporated in carboxylated styrene-butadiene rubber (XSBR) for fabricating XSBR/ND@GO nanocomposites. The morphology and structure of the designed ND@GO nanofiller were investigated comprehensively. A modified latex compounding method was employed to fabricate the rubber/ND@GO nanocomposites to ensure a homogenous dispersion of the nanofiller in the polymer matrix, which was confirmed by high-resolution scanning electron microscopy. The mechanical properties, thermal stability, dynamic rheological, and dynamic mechanical properties of the XSBR/ND@GO nanocomposites were studied. The as-prepared XSBR/ND@GO nanocomposites exhibited superior mechanical properties, thermal stability, and thermo-physical properties attributing to special ND@GO structure and stronger interfacial interactions between the filler and rubber matrix.
Hybrid enhancements by polydopamine and nanosilica on carbon fibre reinforced polymer laminates under marine environment Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-12 Wei Han, Hong-Ping Zhang, Xin Xu, Youhong Tang
In this study, two enhancement methods, i.e., toughen the epoxy matrix by commercially available nanosilica and enhance the interfaces of fibres and matrix by autoxidation of dopamine were applied together in carbon fibre reinforced polymer laminates with potential large-scale applicability. Significant enhancements were found for Mode I interlaminar fracture toughness and interlaminar shear strength with the combined addition of nanosilica and polydopamine in the laminates. The enhancement mechanism is proposed as well. Salt spray tests were applied in this study to simulate a marine environment for the laminates. Model I interlaminar fracture toughness and interlaminar shear strength both decreased under the simulated marine environment with an increase in immersion time, but the deterioration was significantly mitigated when nanosilica and polydopamine were added together with still much higher mechanical properties measured after 3 weeks of salt spray immersion than in neat laminate without salt spray immersion, providing promising evidence for maritime engineering applications of such laminates.
Anisotropic properties of oriented short carbon fibre filled polypropylene parts fabricated by extrusion-based additive manufacturing Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-11 Martin Spoerk, Chethan Savandaiah, Florian Arbeiter, Gerhard Traxler, Ludwig Cardon, Clemens Holzer, Janak Sapkota
Stochastic multi-objective optimisation of the cure process of thick laminates Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-11 K.I. Tifkitsis, T.S. Mesogitis, G. Struzziero, A.A. Skordos
A stochastic multi-objective cure optimisation methodology is developed in this work and applied to the case of thick epoxy/carbon fibre laminates. The methodology takes into account the uncertainty in process parameters and boundary conditions and minimises the mean values and standard deviations of cure time and temperature overshoot. Kriging is utilised to construct a surrogate model of the cure substituting Finite Element (FE) simulation for computational efficiency reasons. The surrogate model is coupled with Monte Carlo and integrated into a stochastic multi-objective optimisation framework based on Genetic Algorithms. The results show a significant reduction of about 40 % in temperature overshoot and cure time compared to standard cure profiles. This reduction is accompanied by a reduction in variability by about 20 % for both objectives. This highlights the opportunity of replacing conventional cure schedules with optimised profiles achieving significant improvement in both process efficiency and robustness.
Atherton–Todd reaction assisted synthesis of functionalized multicomponent MoSe2/CNTs nanoarchitecture towards the fire safety enhancement of polymer Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-08 Junling Wang, Yixin Hu, Cai Wei, Bihe Yuan, Yan Zhang, Wenwen Guo, Weizhao Hu, Lei Song
High fire hazard of thermoplastic polyurethane (TPU) has been an unavoidable obstruction on its comprehensive employment. Here, this work utilizes the physical barrier and promoting charring effect of functionalized multicomponent molybdenum diselenide/carbon nanotubes nanohybrid (HC-Mo) to reduce the fire hazard of TPU. Markedly suppressed heat and smoke releases can be obtained after its addition. With 3.0 wt% HC-Mo dosage, the peak heat release rate (PHRR) is decreased by 38.3%. The peak smoke production rate (PSPR) and peak specific extinction area (PSEA) values are reduced by 32.1 and 35.6%, respectively. Moreover, the toxic volatiles release is obviously inhibited after its incorporation. Furthermore, by incorporating 1.0 wt% HC-Mo, the decreased smoke density is obtained and the total yields of CO and CO2 are decreased by 13.4 and 20.0%, respectively. Overall, HC-Mo shows favorable suppressions function on heat, smoke and toxic gases releases, resulting in the improved fire safety of TPU.
Facile fabrication and performance of robust polymer/carbon nanotube coated spandex fibers for strain sensing Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-07 Qin Chen, Dong Xiang, Lei Wang, Yuhao Tang, Eileen Harkin-Jones, Chunxia Zhao, Yuntao Li
The last decade has witnessed a tremendous growth of research and development in flexible and wearable strain sensors. However, there are still some challenges associated with the fabrication of strain sensors to achieve a high sensitivity and large workable range at low cost. Here, we report on the development of a highly elastic strain sensor based on a commercial spandex fiber coated with a nanocomposite consisting of multi-walled carbon nanotubes (MWCNTs) and thermoplastic polyurethane (TPU) manufactured by a layer-by-layer (LBL) method. The sensor demonstrated outstanding performance with large workable strain, high sensitivity, excellent repeatability and regular signal responses within a wide measuring frequency range of 0.01∼1 Hz. Additionally, the effect of ultraviolet irradiation on the sensor performance was also investigated. Application of the sensor in monitoring diverse human motions, such as facial micro expressions and speech recognition, are also demonstrated showing its potential for applications in wearable devices and intelligent robots.
Microstructure Engineering of Graphene towards Highly Thermal Conductive Composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-07 Haoming Fang, Shu-Lin Bai, Ching Ping Wong
Heat management is more and more crucial challenge since the development of modern electronic devices towards miniaturization and high dense integrity. Highly thermal conductive composites based on graphene are ideal heat-dissipating materials for their excellent heat dissipation ability, outstanding mechanical properties as well as low coefficient of thermal expansion. Numerous efforts have been made towards the development of graphene-based polymeric composites with high performance. Furthermore, it has been demonstrated that microstructure engineering of graphene-based construction of three-dimensional networks and high orientation is extremely important to improve the properties of composites. In this review, the research progress on the latest strategies of microstructure engineering of graphene for highly thermal conductive composites is summarized. Both fabrication methods and theoretical simulations are discussed. Finally, development and perspectives of highly thermal conductive composites are presented.
Creation of individual few-layer graphene incorporated in an aluminum matrix Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-07 Weiwei Zhou, Yuchi Fan, Xiaopeng Feng, Keiko Kikuchi, Naoyuki Nomura, Akira Kawasaki
3D-networks of few-layer graphene (FLG) platelets at grain boundaries, sandwiched between thin amorphous Al2O3 layers, were fabricated by spark plasma sintering (SPS) of graphene oxide (GO)/Al mixed powders. The GO was prepared by a modified Hummers’ method, and was thermally reduced to FLG simultaneously during SPS densification. Subsequent plastic flow of the Al matrix during the hot extrusion process caused the destruction of this structure, rearranged the FLG platelets individually into the uniaxial direction, and made them incorporate in the Al matrix. Observations by high-resolution transmission electron microscopy proved the existence of a direct-contact interface between the FLG and the Al matrix without any interfacial compounds, and revealed that the Al matrix featured a fairly low dislocation density. Consequently, the mechanical strength of Al matrix was noticeably enhanced by FLG incorporation, agreeing with the potential strengthening effect predicted by the load transfer mechanism.
Conductive Shear Thickening Gel/Polyurethane Sponge: A Flexible Human Motion Detection Sensor with Excellent Safeguarding Performance Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-06 Shuaishuai Zhang, Sheng Wang, Yunpeng Wang, Xiwen Fan, Li Ding, Shouhu Xuan, Xinglong Gong
A novel composite with excellent sensing property and safeguarding performance is fabricated by impregnating the carbon black (CB)/shear thickening gel (STG) hybrid into polyurethane sponge (PUS). This STG-CB/PUS composite presents typical shear thickening characteristic, as the storage modulus (G′) rises from 0.21 MPa to 1.52 MPa when shear frequency increases from 0.1 Hz to 100 Hz. Under external strain, the conductivity of STG-CB/PUS varies quickly, thus it can be applied as strain sensors. During the impact, STG-CB/PUS can detect impact stimuli (0.147 mJ – 1450 mJ) and decrease attacking force by 63% simultaneously. Additionally, it is found that the ‘B-O cross bond’ is responded for the shear thickening property and the structure-dependent electrical behaviors contribute to the sensing activity. Finally, a STG-CB/PUS enhanced kneepad is prepared. It possesses a reliable safeguarding performance by reducing 44% attacking force and can effectively trace human body motions such as walking, running and jumping.
Simultaneously enhancing the IFSS and monitoring the interfacial stress state of GF/epoxy composites via building in the MWCNT interface sensor Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-05 Bin Yang, Fu-Zhen Xuan, Hongshuai Lei, Zhenqing Wang, Yanxun Xiang, Kang Yang, Xiaojun Tang, Wenyan Liang
This paper presents an effective technology that could simultaneously enhance the interfacial shear strength (IFSS) and monitor the interfacial stress state between glass fiber and epoxy vinyl ester resin (GF/epoxy). Muiti-walled carbon nanotube (MWCNT) was added to aqueous surfactant solution and dispersed by ultrasonic. Subsequently, MWCNT was deposited on GF surface by physical vapor deposition. The results show that the sensing performance of the developted sensor was dependence on MWCNT solution concentration, interface length, ultrasonic dispersion duration, and immersion cycles. Fiber-bundle pull-out tests show that IFSS of GF/epoxy was enhanced by incorporating MWCNT into the interphase. By measuring resistance change of the MWCNT sensor, the interfacial evolution behaviour was monitored during the pull-out test. The results indicate that the presented technology can be successfully used for in-situ sensing the accumulated interfacial damage and simultaneously enhancing the IFSS of GF/epoxy composites.
Viscoelastic response of carbon fibre reinforced polymer during push-out tests Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-05 Santiago Corujeira Gallo, Xiaoying LI, Zhenxue Zhang, Constantinos Charitidis, Hanshan Dong
On the interplay behavior of fatigue crack growth and delamination of Ti/Cf/PMR polyimide hybrid laminates under overloading Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-05 Kai Jin, Yanyan Lin, Kai Chen, Huaguan Li, Jie Tao
The effect of overload on the fatigue crack growth and delamination of the Ti/Cf/PMR (Polymerization of Monomeric Reactants) polyimide hybrid laminates and the interplay behavior between crack growth and delamination were studied by applying single-peak, multi-peak, and block overloads. The retardation effect was discovered under variable overloads. The mechanism of crack growth and delamination was also analyzed. It was found that the crack grew perpendicular to the fiber direction and the initiation site of delamination always located around the micro-cracks of metal layers. The delamination growth was affected by the maximum stress level and the stress sequence. The interplay between crack growth and delamination on fatigue failure of Ti/Cf/PMR polyimide hybrid laminates could accelerate the crack growth and delamination extension.
In situ shear-induced mercapto group-activated graphite nanoplatelets for fabricating mechanically strong and thermally conductive elastomer composites for thermal management applications Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-04 Yinhang Zhang, Soo-Jin Park
Interfacial interaction is one of the most crucial and dominant factors affecting the performance and behavior of a material. The surfaces of layered expanded graphite (EG) were activated by covalently grafted mercapto groups (-SH), which can readily react with the macromolecular chains of rubber, thus forming a strong interfacial adhesion between the filler and the rubber matrix. Shear-induced mercapto-group-activated graphite nanoplatelets (S@GNPs) were fabricated in situ by compound mixing in a two-roll mill. A correlation between the interfacial interaction and the thermal conductivity, as well as the thermo-physical properties, was comprehensively investigated. The results showed that rubber/S@GNP composites exhibited better mechanical performance, enhanced thermo-physical properties, and superior thermal conductivity, all of which could be attributed to the stronger interfacial interaction resulting from chemical bonding between the S@GNPs and the molecular chains of the rubber, relative to XSBR/GNP composites connected by weaker π-π stacking.
Assessment of F-III and F-12 aramid fiber/epoxy interfacial adhesions based on fiber bundle specimens Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-02 Guocheng Qi, Boming Zhang, Shanyi Du
In this work, the normal bonding and longitudinal shear adhesion properties of F-III and F-12 aramid fiber/epoxy interfaces were estimated by transverse fiber bundle tension (TFBT) test and 45° fiber bundle tension (45FBT) test, respectively. After the tensile tests, the micro failure mechanisms were investigated by observing the fracture surfaces of the fiber bundle samples using scanning electron microscope (SEM). The interfacial debonding was found coupled with fibrillation at the fiber surface. The different macro failure modes of TFBT and 45FBT samples were subsequently explained via finite element (FE) calculation. The applicability of the fiber bundle tests for the characterization of aramid fiber/matrix interfacial adhesion was eventually discussed.
Optical HDR Acquisition of Crack Density Evolution in Cyclic Loaded GFRP Cross-Ply Laminates Affected by Stitching Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-06-01 J.J. Bender, J.A. Glud, E. Lindgaard
The fatigue crack density evolution in a cross-ply laminate where edge finish and stitching are taken into account is investigated. Diamond saw and water jet cutting are used to produce the test specimens and some of the specimens are polished afterwards. The crack density evolution and crack initiations are tracked automatically. It is shown that the number of cracks initiating at the edges for non-polished specimens are similar, whereas the diamond saw cut and polished specimens have fewer cracks at the edges, and the water jet cut and polished specimens have even fewer. In addition it is shown that the crack density is higher in the stitching areas than in the rest for polished specimens. This indicates that the stitching is highly governing of where cracks initiate and propagate in the specimens with limited edge defects. The same applies to real composite structures, which are negligibly affected by edge defects.
The influence of hardener-to-epoxy ratio on the interfacial strength in glass fibre reinforced epoxy composites Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-30 Ross F. Minty, Liu Yang, James L. Thomason
This work seeks to develop a better understanding of the influence that the chemistry of an epoxy thermoset system has on the stress-transfer capability of the fibre-matrix interface. We discuss the correlation between the interfacial shear strength (IFSS) and the properties of the matrix such as glass transition temperature (Tg), storage modulus and linear coefficient of thermal expansion (LCTE). The results indicate that each is strongly dependent on the hardener-to-epoxy ratio and it was found that changes in IFSS can be related to changes in the thermomechanical properties of the matrix. From the results presented it is hypothesized that residual radial compressive stresses at the interface are influenced by the chemistry of the matrix system due to the changes in the properties of the matrix. The combination of these residual stresses with static friction may lead to a potential variation of the interfacial stress-transfer capability in glass-fibre reinforced epoxy composites.
The influence of oxygen containing functional groups on carbon fibers for mechanical properties and recyclability of CFRTPs made with in-situ polymerizable polyamide 6 Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-31 Toshihira Irisawa, Ryohei Inagaki, Junya Iida, Ryosuke Iwamura, Kento Ujihara, Sarasa Kobayashi, Yasuhiro Tanabe
The influence of the oxygen containing functional groups on carbon fibers for mechanical properties and recyclability of carbon fiber reinforced thermos-plastics (CFRTPs) made with in-situ polymelizable polyamide 6 (PA6) have been discussed. Interfacial adhesion between CFs with functional groups and PA6 became higher compared with that of because of the interaction such as hydrogen bond, covalent bond. Furthermore, it was revealed that these effects apparently improved the mechanical properties of the CFRTPs. On the other hand, the interaction between the functional groups and PA6 affected the recyclability of the CFRTPs. Although PA6 as the matrix polymer of the CFRTP could be pyrolyzed even under N2 gas and recycle CFs with very little char could be obtained at 600 oC, it was found that the tensile strength decreased after pyrolytic process by about 10 % only when the CFs with the functional groups were used for reinforcement fibers.
Degradation mechanism of carbon fiber-reinforced thermoplastics exposed to hot steam studied by chemical and structural analyses of nylon 6 matrix Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-31 Hideaki Hagihara, Ryota Watanabe, Tomio Shimada, Masahiro Fanabashi, Masao Kunioka, Hiroaki Sato
Degradation testing of nylon 6-based carbon fiber-reinforced thermoplastic (CFRTP) was performed by exposure to hot steam in a closed vessel. The degraded structure was investigated to understand the degradation mechanism. Aging-induced micro-cracking in the nylon 6 matrix of CFRTP indicated that stress was likely generated by changes in its local density along with a decrease in the molecular weight due to hydrolysis. Aging process of nylon 6 increased the free volume hole size in the amorphous part and also induced crystallization, suggesting that the density of the amorphous part decreases with increasing crystallinity in the matrix. Therefore, the degradation mechanism of the CFRTP was proposed to begin with a change in the local density of nylon 6 owing to crystallization, followed by water infiltration and hydrolysis of the matrix. Stress due to density changes combined with reduced molecular weight forms micro-cracks, decreasing the mechanical strength of CFRTP.
Evolvement of microstructure and electrical property in the conversion of high strength carbon fiber to high modulus and ultrahigh modulus carbon fiber Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-28 Xin Qian, Jianhai Zhi, Liqun Chen, Junjun Zhong, Xuefei Wang, Yonggang Zhang, Shulin Song
Evolvement of microstructure and electrical property in the conversion of high strength carbon fiber (HSCF) to high modulus carbon fiber (HMCF) and ultrahigh modulus carbon fiber (UHMCF) was investigated. Longitudinal grooves on fiber surfaces became less well-defined during high temperature graphitization. The tensile modulus of carbon fibers was affected by fiber crystalline structure and it increased with decreases in the value of interlayer spacing and improvements in the value of crystallite thickness. Increases in the crystallite size almost had little effect on the tensile strength. However, a lower interlayer spacing and a higher preferred orientation could result in a higher tensile strength. The crystal structure of carbon fibers became much more ordered during high temperature graphitization. It was found that the electrical resistivity gradually decreased from 14.69×10-4 Ω·cm to 9.70×10-4 Ω·cm and 8.80×10-4 Ω·cm, respectively, in the conversion of HSCF to HMCF and UHMCF.
Continuous carbon nanotube synthesis on charged carbon fibers Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-28 David B. Anthony, XiaoMeng Sui, Israel Kellersztein, Hugo G. De Luca, Edward R. White, H. Daniel Wagner, Emile S. Greenhalgh, Alexander Bismarck, Milo S.P. Shaffer
Carbon nanotube grafted carbon fibers (CNT-g-CFs) were prepared continuously, spool to spool, via thermal CVD. The application of an in-situ potential difference (300 V), between the fibers and a cylindrical graphite foil counter electrode, enhanced the growth, producing a uniform coverage of carbon nanotubes with diameter ca. 10 nm and length ca. 125 nm. Single fiber tensile tests show that this approach avoids the significant reduction of the underlying carbon fiber strengths, which is usually associated with CVD grafting processes. Single fiber fragmentation tests in epoxy, with in-situ video fragment detection, demonstrated that the CNT-g-CFs have the highest interfacial shear strength reported for such systems (101 ± 5 MPa), comparable to state–of–the–art sizing controls (103 ± 8 MPa). Single fiber pull-out data show similar trends. The short length of the grafted CNTs is particularly attractive for retaining the volume fraction of the primary fibers in composite applications. The results are compared with a short review of the interfacial data available for related systems.
Lightweight chopped carbon fibre reinforced silica-phenolic resin aerogel nanocomposite: facile preparation, properties and application to thermal protection Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-28 Chonghai Wang, Haiming Cheng, Changqing Hong, Xinghong Zhang, Tao Zeng
A chopped carbon fibre (CF) reinforced silica-phenolic resin (Si/PR) aerogel nanocomposite was prepared through a simple one-pot sol-gel polymerization in a slurry of CF, PR, silane, hexamethylenetetramine and ethylene glycol. CFs were distributed homogeneously and randomly in the Si/PR aerogels. The Si/PR aerogels exhibit finer microstructure, higher thermal stability and better anti-oxidation resistance than PR aerogels. The compressive strength for the composites with low densities between 0.402 to 0.463 g/cm3 ranged from 0.33 to 2.44 MPa and thermal conductivities from 0.089 to 0.116 W/(mK), respectively. Furthermore, the CF/Si/PR aerogel nanocomposites could deliver linear ablation rates as low as 0.117 mm/s, and internal temperature peaks approximately 100 °C at 38 mm in-depth position as the surface temperature exceeded 2000 °C in oxyacetylene flame. From mentioned above, this lightweight composite presents huge application prospects in thermal protection and heat insulation field, especially in aerospace industry.
Highly efficient catalysts for reducing toxic gases generation change with temperature of rigid polyurethane foam nanocomposites: A comparative investigation Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-28 Yao Yuan, Bin Yu, Yongqian Shi, Chao Ma, Lei Song, Weizhao Hu, Yuan Hu
Huge consumption of rigid polyurethane foam (RPUF) brings about two serious challenges for our society: fire hazards and environmental pollution. To address these issues, metal oxides and bimetallic oxides used for reducing smoke toxicity was successfully synthesized. The structures and morphologies were confirmed and thermogravimetric analysis indicated that incorporation of 2 wt% NiO conspicuously increased the residual yield of RPUF nanocomposites by 63.8% due to its catalytic coupling effect. Additionally, through the thorough analysis of volatile and condensed products, the smoke toxicity suppression mechanism in the pyrolysis and combustion of RPUF was investigated so as to find out the conversion of CO to CO2 through a redox cycle, involving the reduction of Ni+-Ni0 by CO and the oxidation of Ni0-Ni+ by O2. Among all the additives, nickel molybdate is the best catalyst which facilitates the migration of fuel-N in RPUF into the pollution-free gas in pyrolysis and combustion process.
Highly boosting the interlaminar shear strength of CF/PEEK composites via introduction of PEKK onto activated CF Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-28 Elwathig A.M. Hassan, Dengteng Ge, Lili Yang, Jianfeng Zhou, Mingxia Liu, Muhuo Yu, Shu Zhu
Thermal and ablation properties of EPDM based heat shielding materials modified with density reducer fillers Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-29 Marco Rallini, Ivan Puri, Luigi Torre, Maurizio Natali
EPDM/aramid fibers ablatives represent the state of the art of Elastomeric Heat Shielding Materials (EHSMs) for Solid Rocket Motors (SRMs). EPDM exhibits the lowest density among elastomers maximizing the payload of a SRM. Due to necessity to further maximize the payload of a rocket, density reducer fillers, such as glass or phenolic microballoons, can be considered in the material formulation of the SRM insulation liner. However, the open literature on EPDM based EHSMs combined with these density reducers is extremely limited because these formulations are generally proprietary of companies manufacturing SRMs. In our paper we studied the heat capacity, thermal and dimensional stability, mechanical properties, and ablation resistance of EPDM based EHSMs combined with glass microspheres at different percentages. The main aim was to evaluate Perlite, an affordable density reducer additive commonly used in concrete applications, as a possible replacement of glass microballoons.
Anisotropic Thermally Conductive Composite with Wood-derived Carbon Scaffolds Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-21 Li Chen, Na Song, Liyi Shi, Peng Ding
In this study, we reported a thermally conductive composite with wood-derived 3D scaffold. The composites were easily fabricated by impregnating the polyamide-imide (PAI) into the wood scaffold and then in-situ carbonized. The well-aligned cellulose mircochannels in natural wood are maintained during the carbonization, leading to the improved anisotropic thermal conductive properties of the composite. The thermal conductivity of the composite reached 0.56 W· · m-1· · K-1 in cross-plane direction increasing by 250% and 0.22 W· · m-1· · K-1 in parallel direction, increasing by 37.5%, respectively. The unique structure of the composite also plays an important role in enhancing the mechanical performance. The Young's modulus of the composite in vertical direction reached to 451.9 MPa, 4-times higher than that of natural wood in the same orientation. The integrated performance of the composites could be attributed to the alignment of cellulose nanofibers inherited from the natural wood. This study will provide an innovative design and fabrication of composite for thermal management.
Multifunctional cementitious composites modified with nano- titanium dioxide: A review Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-21 Zhen Li, Siqi Ding, Xun Yu, Baoguo Han, Jinping Ou
Nano titanium dioxide (NT) as a zero-dimensional nano material has received widespread attention from both industry and research communities due to its distinguished physical and chemical properties. Much research work indicated that NT can modify material structures, thus providing a new approach to develop high-performance, durable, multifunctional, and environmentally friendly cementitious composites. This paper reviews state-of-the-art research carried out on the effect of NT on the properties of cementitious composites and aims to provide a comprehensive insight into possible development of NT-engineered cementitious composites. The detailed introductions on the processing, microstructures (hydration products and pore structure), properties (hydration, workability, density, mechanical properties, shrinkage, functional properties and durability) and applications of NT-engineered cementitious composites are presented. Finally, the risks, challenges and future development of NT-engineered cementitious composites are discussed.
High residual mechanical properties at elevated temperatures of carbon fiber/acetylene-functional benzoxazine composite Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-21 Bao-Gang Sun, Kun-Xiao Yang, Qin Lei, Han-Qiao Shi, Yuan-Qing Li, Ning Hu, Shao-Yun Fu
It is always of great practical significance to develop carbon fiber (CF) reinforced polymer composites with high residual mechanical properties at elevated temperatures for aerospace engineering structures, etc. In this work, the CF reinforced composite based on acetylene-functionalized benzoxazine (AFBEN) was manufactured by the resin transfer moulding (RTM) technology. The mechanical properties at elevated temperatures (150-350°C) are first and systematically examined for the as-prepared CF/AFBEN composite. Differential scanning calorimetry and rheological characteristics are employed to evaluate the adaptability of AFBEN for the RTM process. Dynamic mechanical and thermogravimetric properties of the CF/AFBEN composite are also investigated to evaluate the thermal stability. The results display that the mechanical strengths of the CF/AFBEN composite exhibit the high residual rates of ca. 90% at 250°C and over 60% at 350°C compared to the mechanical properties at room temperature. The fracture mechanisms at room and elevated temperatures are studied and the fracture behavior of the CF/AFBEN composite is shown to transform from fiber-matrix interfacial debonding to resin matrix failure as the temperature increases. Consequently, the as-prepared CF/AFBEN composite show great potentials for practical applications in aerospace engineering structures, etc. due to its high residual mechanical properties at elevated temperatures and the ease of the RTM processing.
X-Ray Micro-computed-tomography Characterization of Cracks Induced by Thermal Cycling in Non-crimp 3D Orthogonal Woven Composite Materials with Porosity Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-21 Marco Gigliotti, Yannick Pannier, Raquel Antoranz Gonzalez, Marie-Christine Lafarie-Frenot, Stepan V. Lomov
This paper focuses on an experimental study of the thermal cycling behavior of a carbon fiber/epoxy matrix composite material reinforced with a non-crimp 3D orthogonal woven preform (3DNCOW). The aim is to characterize the damage mechanisms – i.e. matrix cracking - induced by thermal cycling thanks to X-ray micro-computed-tomography (µCT). Qualitative and quantitative descriptions of the morphology and the evolution of cracks with thermal cycling are carried out through the analysis of µCT scans of samples at different cycle numbers. In addition, since the specimens have a certain level of porosity due to the infusion process, a complete description of this defect is carried out, and its influence on the damage mechanisms induced by thermal cycling is analyzed.
Tailoring the structure and mechanical properties of graphene nanosheet/aluminum composites by flake powder metallurgy via shift-speed ball milling Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-21 Yuanyuan Jiang, Zhanqiu Tan, Run Xu, Genlian Fan, Ding-Bang Xiong, Qiang Guo, Yishi Su, Zhiqiang Li, Di Zhang
Graphene nanosheet (GNS)/aluminum composites were fabricated via shift-speed ball milling (SSBM), consisting of a long-term low-speed ball milling (LSBM) and a short-term high-speed ball milling (HSBM). During the early stage of LSBM, Al powders were flattened into flakes, while the agglomerated GNSs were gradually dispersed onto Al flakes. After an inflection point of LSBM time, the dispersed GNSs got re-agglomerated and seriously damaged due to the accumulated work-hardening of Al flakes. During HSBM, the GNS/Al flakes were cold-welded into lamellar-structured particles, preserving the GNS dispersion states. It was demonstrated that the 0.5 vol.% GNS/Al composites via SSBM with 6 h LSBM had proper combination of ultrafine-grained Al matrices with well-preserved, uniformly-dispersed GNSs. Exceptional properties were achieved with a good ductility of 13.5% at a tensile strength of 295 MPa. Therefore, such flake powder metallurgy via SSBM proved to be a smart and effective fabrication strategy for nano-reinforced metal matrix composites.
Micro-configuration controlled interfacial adhesion by grafting graphene oxide onto carbon fibers Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-19 Xiaomin Yuan, Bo Zhu, Xun Cai, Kun Qiao, Shengyao Zhao, Min Zhang, Junwei Yu
An effective way to enhance the interfacial properties of carbon fiber reinforced polymer composite (CFRPs) was proposed by preparing graphene oxide (GO)/carbon fiber (CF) hybrid fibers through electrophoretic deposition. The influence of different deposition parameters on the microstructure of GO/CF hybrid fibers were synthetically investigated in order to understand the micro-configuration and bonding mechanism. Note that GO deposition was highly effective in adjusting fiber surface physiochemical characteristics and constructing a strengthened interface. When utilizing a 20V-15min deposition technology under alkalescent condition (pH=10), the introduction of GO on CF surface was feasible to toughen CFRPs, exhibiting substantial interfacial shear strength and interlaminar shear strength improvements of 14.8% and 37.3%, respectively. Meanwhile, three micro-configuration models were proposed to categorize the bonding mechanism of GO/CF hybrid fibers, namely, ‘Grafting’, ‘Coating’ and ‘Plastering’ deposition. Overall, the high mechanical performance achieved in this work are comparable or better than those of many previously reported researches.
Advanced short fiber composites with hybrid reinforcement and selective fiber-matrix-adhesion based on polypropylene - Characterization of mechanical properties and fiber orientation using high-resolution X-ray tomography Compos. Part A Appl. Sci. Manuf. (IF 4.514) Pub Date : 2018-05-19 C. Kahl, M. Feldmann, P. Sälzer, H.-P. Heim
Composites with two types of reinforcement fibers open a large field of opportunities and combine properties. Glass fibers lead to higher strength and modulus, but they provide a brittle character. In contrast to this, man-made cellulose fiber composites show higher energy absorption and higher elongation-at-break. The aim of this study is to investigate the synergy of those two fiber types in a hybrid compound. Compounds with an overall fiber content of 16 vol-% and different ratios of glass and man-made cellulose fibers were prepared with a twin-screw extruder and injection molded to test specimen. Mechanical properties as well as the composite morphology were studied for compounds with selective fiber-matrix-adhesion and without a coupling agent. A bimodal fiber length distribution was found in the hybrid compounds due to the different shortened fiber types. The long man-made cellulose fibers increase the impact strength and influences the fiber orientation in the hybrid.
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