Comparative study on metal/CFRP hybrid structures under static and dynamic loading

https://doi.org/10.1016/j.ijimpeng.2020.103509Get rights and content

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  • Experimentally and numerically investigated the crashworthiness of Metal/CFRP hybrid structures under quasi-static and dynamic loading conditions.

  • Explored the energy absorption mechanics of the hybrid tubes.

  • Explored the influences of aluminum wall thickness, fiber orientation and interfacial strength on crashworthiness of the hybrid tubes.

Abstract

This study aims to explore the crushing behavior of aluminum (AL) - carbon fiber reinforced plastic (CFRP) tubes with different hybrid configurations subjected to quasi-static and dynamic loading conditions. First, a series of experimental tests are carried out to explore the crushing behaviors of hybrid tubes in comparison with the corresponding individual tubes made of single material. The experimental results indicate that the H-II hybrid tube, made of an outer aluminum circular tube and internally adhered CFRP layers, generates a unique deformation pattern; whose outer aluminum tube inverses externally and inner CFRP layers crush progressively. With these distinctive deformation features, the H-II hybrid tubes are considered to be ideal with superior crashworthiness and energy-absorbing capacity. It is also found that loading rate has little influence on deformation pattern of hybrid tubes and single material tubes, while energy-absorbing capacity of hybrid tubes and individual CFRP tubes under dynamic loading are substantially lower than those under quasi-static loading. Second, numerical simulations are performed for the H-II hybrid tubes to provide further insights into their underlying energy-absorbing mechanisms. It is found that the external inversion mode of the outer aluminum tube is the major energy-absorbing mechanism, in which the contribution of the outer aluminum tube to total energy absorption decreases with increase in thickness of CFRP layers. The internal energy of the externally inversed aluminum tube is considerably higher than internal energy of typical progressively-folded AL tube (sole aluminum tube). Third, a parametric study is further conducted, which indicates that with increasing aluminum wall thickness, the specific energy absorption (SEA) increases. Besides, it is found that varying fiber orientation of inner CFRP layers leads to no evident change in the deformation mode and SEA of the H-II hybrid tubes. When the interfacial strength in between aluminum and CFPR reaches a certain level, there is no evident increase in the total energy absorption with further increase of the interface strength, but the initial peak crushing force increases notably. These results are expected to deepen the understanding of crushing behavior of the H-II hybrid tubes, thereby providing guidance for the crashworthiness design.

Introduction

Over the past few decades, rising requirements in fuel consumption, environmental regulations and road safety have presented great challenge for automotive industry. Accordingly, more advanced energy-absorbing components are being developed by applying high performance and lightweight materials and structures [1]. Tailor rolled blank [2,3], auxetic structures [4], [5], [6], porous materials [7,8] and composite materials [9], [10], [11] are some typical examples in balancing lightweight and performance. Of the abovementioned lightweight materials and structures, carbon fiber reinforced plastics (CFRP) composites have attracted significant attention attributable to their unique mechanical properties and excellent design flexibility, in which substantial research efforts have been increasingly devoted on how to use CFRP for structural design of automotive industry. For example, Zhu et al. [12] numerically investigated crashworthiness characteristics of CFRP bumper beam with variable cross-sections, and they found that the developed novel bumper beam was of superior mechanical performance. Liu et al. [13] experimentally studied crushing behaviors of double hat shaped CFRP tubes, and they found that tubal wall thickness is a critical parameter determining the failure mode and energy-absorbing capability. Boria et al. [14] experimentally explored crushing behaviors and energy-absorbing capability of CFRP truncated cones, in which two typical crushing failure modes were identified. Waimer et al. [15] developed the numerical approach to modeling failure mechanisms of CFRP components under dynamic crash loads. Zhu et al. explored energy-absorbing mechanisms of CFRP multi-cell structures by using experimental and numerical approaches [16]. Mamalis et al. [17] carried out a series of axial compressive tests to explore the crushing behaviors, collapse modes and crashworthiness characteristics of CFRP square tubes. Zhao et al. [18] numerically investigated crushing behavior of several CFRP tapered tubes with various cross-sectional profiles and tapered angles under multiple load cases, and they found that there was a positive correlation between total energy-absorbing capacity and number of edges in the cross section. Ren et al. [19] and Jiang et al. [20] developed an accurate progressive failure model based upon continuum damage mechanics to investigate crushing behaviors of CFRP corrugated beam under quasi-static axial crushing load. Ataabadi et al. [21] experimentally explored the influences of lay-up configuration on energy-absorbing capability of CFRP tubes under axial loading conditions. In light of these abovementioned studies, it is known that CFRP materials demonstrate considerable potential in lightweight design for crashworthiness design of vehicle structures.

Nevertheless, recent research has indicated that the high material cost of CFRP is not suitable for mass production of vehicle components [22]. For this reason, an appropriate trade-off between material cost and weight reduction needs to be made. In addition, it is also found that CFRP structures are susceptible to damage from impact loading, leading to significant reduction in energy absorption [23]. Fortunately, these shortcomings could be overcome by a rationally designed hybrid structure, in which each constituent phase could present its own characteristics contributing to the overall performance synergistically. For example, the metal/CFRP hybrid structures, which combine the low density and high strength CFRP materials with low cost and high toughness metallic materials, exhibit great potential in achieving mingled features of lightweight and competitive material cost.

Over the past few decades, metal/CFRP hybrid structures have been developed for crashworthiness purposes. In this regard, for example, Song et al. [24] studied dynamic crushing behaviors of the hybrid tubes, which were fabricated with the metallic tubes externally wrapped with composite layers. Bambach et al. [25], [26], [27] experimentally studied the crashworthiness of hybrid square tubes, and then they numerically investigated these hybrid structures for vehicular applications. Their study exhibited that the hybrid components were able to improve crashworthiness and reduce weight. Zhu et al. [28,29] and Wang et al. [30] studied crashing characteristics of different hybrid columns under axial and oblique quasi-static loading conditions; and they demonstrated the superior crashworthiness characteristics and competitive material costs of such hybrid structures. Imran et al. [31] explored axial compression capacity of steel columns externally reinforced by CFRP. They found that axial crushing capacity of the hybrid column increased up to 2.6 times of that of the steel columns, indicating the superior performance of the hybrid columns. Dlugosch et al. [32] studied the axial crashing characteristics and crashworthiness of several metal/CFRP hybrid square tubes; and they further developed a simplified modeling approach to effectively evaluating structural behavior in an early stage of crashworthiness design. Lee et al. [33] applied steel/CFRP hybrid composites in center-pillar reinforcements through experimental and numerical approaches, in which considerable advantages in lightweight and crashworthiness were demonstrated by comparing with the tailor welded blank (TWB) counterparts. From these aforementioned studies, it has demonstrated that the metal/CFRP hybrid structures possess superior mechanical performance and competitive material cost; and consequently, they are more suitable to be used for vehicular components.

It is noted that most of the metal/CFRP hybrid structures considered in the previous studies consisted of an inner metallic column and externally bonded CFRP layers. Nevertheless, it was shown that the outer CFRP layers of these hybrid columns are bent externally with formation of considerably large fragments during crushing process, which might result in a relatively lower damage level of CFRP [29]. Thus, the configuration of such a hybrid column may not take a full advantage of CFRP. In other words, it is worth exploring other hybrid configurations for achieving better crashworthiness behavior.

This work aims to study axial crashing characteristics of aluminum/CFRP columns with different hybrid configurations under different loading conditions by comparing with net aluminum and net CFRP counterparts (i.e. individual tubes made of single material). Specifically, two groups of aluminum/CFRP columns with different hybrid schemes are fabricated. The first group comprises an inner aluminum tube and externally wrapped with the CFRP layers, named as H-I hybrid tubes; and the second group comprises an outer aluminum tube and internally adhered CFRP layers, named as H-II hybrid tubes. First, a series of axial crushing tests with quasi-static and dynamic loading conditions are respectively carried out to explore their crushing behavior; and their energy-absorbing characteristics and crashworthiness are compared with those of net aluminum and net CFRP tubes. Second, the numerical simulations are conducted to provide further insights into the underlying energy-absorbing mechanisms which are unobservable with the experimental means available. Finally, a systematic parametric study is conducted to quantitatively explore the influences of tubal wall thickness, fiber orientation and interfacial strength on crushing behavior of the hybrid tubes.

Section snippets

Specimens fabrication

Two groups of aluminum/CFRP hybrid tubes are fabricated to perform the experimental study here. To enable the comparison, the corresponding net aluminum circular tube and CFRP tube are prepared as well, and all the different specimens are summarized in Fig. 1. According to Fig. 1, the CFRP tube with a larger diameter, named as "CFRP-L", has the same geometric dimensions as the outer CFRP layers of the type H-I hybrid tubes; and the CFRP tube with a smaller diameter, named as "CFRP-S", have the

Crushing process and force-displacement curves

The crushing processes and force-displacement curves are compared for the tests under quasi-static and dynamic loading, in which the deformation behavior, crashworthiness and the effect of loading rate are investigated in detail.

Numerical modeling

Fig. 24(a) presents a representative finite element (FE) model with specific boundary and loading conditions in commercial FE code ABAQUS/Explicit. The tube is compressed by the simulated moving upper rigid platen, and the lower rigid platen is fixed. To be consistency with the experimental tests, a lumped mass of 320 kg is established in the center of the upper platen, which has the initial impact velocity of 5 m/s; and the bottom end of the column is fixed to the lower platen. The CFRP-S tube

Parametric studies

Based upon the validated FE models, this sub-section further explores the influences of design parameters such as aluminum wall thickness, fiber orientation and interfacial strength on crashing characteristics of the H-II hybrid tubes by comparing their crashworthiness indicators, crushing process and energy-absorbing mechanisms.

Conclusion

This study explores the crushing behavior of two groups of aluminum/CFRP hybrid tubes subjected to quasi-static and dynamic loading conditions by using experimental and numerical techniques, respectively. In the experimental studies, several key crashworthiness indicators and the crushing process of the hybrid tubes are investigated by comparing with corresponding individual tubes. The underlying energy-absorbing mechanisms and the influence factors on crashworthiness of the H-II hybrid tubes

Author contribution statement

Guangyong Sun and Guohua Zhu designed the research scheme and wrote the manuscript, Jiapeng Liao and Guohua Zhu conducted the experimental tests and numerical simulations, Qing Li analyzed the numerical results and revised the manuscript.

Declaration of Competing Interest

The authors declared that they have no conflicts of interest to this work.

Acknowledgement

This work is supported by National Natural Science Foundation of China (51575172, 51905042). Dr Guangyong Sun is a recipient of the Australian Research Council (ARC) Discovery Early Career Researcher Award (DECRA).

References (44)

  • M. Waimer et al.

    Simulation of CFRP components subjected to dynamic crash loads

    Int J Impact Eng

    (2017)
  • G. Zhu et al.

    Energy-absorbing mechanisms and crashworthiness design of CFRP multi-cell structures

    Compos Struct

    (2020)
  • A.G. Mamalis et al.

    Crashworthy characteristics of axially statically compressed thin-walled square CFRP composite tubes: experimental

    Compos Struct

    (2004)
  • X. Zhao et al.

    Crashworthiness analysis and design of composite tapered tubes under multiple load cases

    Compos Struct

    (2019)
  • Y. Ren et al.

    A progressive intraply material deterioration and delamination based failure model for the crashworthiness of fabric composite corrugated beam: parameter sensitivity analysis

    Compos Part B

    (2018)
  • H. Jiang et al.

    Research on the progressive damage model and trigger geometry of composite waved beam to improve crashworthiness

    Thin-Walled Struct

    (2017)
  • J. Meredith et al.

    A performance versus cost analysis of prepreg carbon fiber epoxy energy absorption structures

    Compos Struct

    (2015)
  • H.C. Kim et al.

    Crashworthiness of aluminum/CFRP square hollow section beam under axial impact loading for crash box application

    Compos Struct

    (2014)
  • H.W. Song et al.

    Axial impact behavior and energy absorption efficiency of composite wrapped metal tubes

    Int J Impact Eng

    (2000)
  • M.R. Bambach et al.

    Axial capacity and design of thin-walled steel SHS strengthened with CFRP

    Thin-Walled Struct

    (2009)
  • M.R. Bambach

    Fiber composite strengthening of thin-walled steel vehicle crush tubes for frontal collision energy absorption

    Thin-Walled Struct

    (2013)
  • M.R. Bambach

    Fiber composite strengthening of thin steel passenger vehicle roof structures

    Thin-Walled Struct

    (2014)
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