Elsevier

Composites Communications

Volume 23, February 2021, 100590
Composites Communications

Deep drawing of fiber metal laminates using an innovative material design and manufacturing process

https://doi.org/10.1016/j.coco.2020.100590Get rights and content

Highlights

  • Importance of optimized FMLs material design and deep drawing process.

  • Forming FMLs in No-cured condition and hot-pressing improved the wall homogeneity.

  • Forming FMLs using multi glass fiber patches enhance the formability.

Abstract

Fiber-Metal Laminates (FMLs) have gained increasing attention in the advanced industry due to their unique structural reliability, weight reduction, and improved damage tolerance. Nevertheless, the existing forming approaches are not well qualified for the high-volume manufacturing of small and complex laminate components. With the forming of FMLs, the cured fiber and resin matrix layers are deformed elastically, and the metal layers are deformed plastically. The attainable deformation is depending on the strain amount can endure by the glass fibers and by the strength of the interface among the layers. In current research work at the department of aircraft manufacturing engineering at Beihang University, a promising cost-effective approach for the automated mass production of small parts made of FMLs was proposed using new material design and manufacturing process. The new process combined an optimized inner glass fiber patches and non-cured FMLs, followed by the Hot-pressing. Results were very encouraging and exhibited that FML parts manufactured by using this new preparation and process may pave the way for industrial-scale utilization.

Introduction

The innovations in the hybrid materials field have provided important weight saving and structural reliability. Fiber-metal Laminates (FMLs) have been subject to the permanent interest of several experts over the last decades, such as aerospace, marine, and military industry [1]. FMLs defined as a mixture of sheet metals and fibers, stuck by an adhesive. Based on the properties of its constituents, these FMLs have the ability to adjust the whole mechanical properties of the sandwich material [2]. FMLs structures have proved a success in their application in low volume defense and aerospace industry because of their excellent impact properties and fatigue resistance [3,4]. GLARE materials belong to the FMLs family, made of a thin aluminum sheet as a skin and a core of unidirectional glass fiber layers impregnate in an adhesive system. Compared to monolithic metals, GLARE laminates also provide better stiffness and strength [5,6]. This makes GLARE laminate the material of choice for various challenging applications. Research's exhibited the advantages in performance and the weight saving of the GLARE structure. But they also mentioned the high production cost of these parts in comparison with metal structures [[7], [8], [9]]. However, the biggest obstacle to employ these FMLs in mass production is to find a good manufacturing process to produce a small complex-laminate parts. Several studies have investigated the FMLs forming behavior; results are in agreement that forming FMLs with the conventional deep drawing methods leads to the early fracture of the laminate without achieving a significant depth [[10], [11], [12], [13]]. FML forming is often accompanied by the appearance of cracks in the bending region, delamination, and fibers tearing. All these leads to the restricted formability of the laminates. This is mainly influenced by the material's property, like the matrix viscosity and fiber orientation. As well by forming parameters such as the punch forming speed and the blank holding force (BHF) [14]. Furthermore, the elongation of the fibers has very low formability; the elongation at break for the glass fibers is around 4–6% [15]. Metals and their alloys can endure the elastic and plastic state through the deep drawing procedure. Due to their atomic structure have approximately isotropic mechanical features, and have higher strain at failure than FMLs, mostly around 10 and 50% [16]. Unlike monolithic metals, FMLs are made of fiber-matrix material, and their constituents need to be examined separately. The mechanical properties of fibers are very different in the fiber direction and the transverse direction. In the conventional stamp forming, the thermo-setting matrix needs to be cured from a viscous state to the solid-state, and then the blanks transfer to the forming step. The curing process is controlled by temperature and time. And it is one of the main reasons which lead to early failure due to the solid-state of the resin [17,18]. Furthermore, the long curing time increases production time and affect efficiency. Researchers also have tried forming FMLs using non-cured laminate where fibers are positioned by hand after that wet with resin. They found that hydrostatic conditions inside the matrix material happen due to the applied pressure; this makes the resin to move into the flange edge area [14]. Authors of the works [19,20] proved that using semi-cured GLARE had a good effect on reducing the failure severity of the laminate during deep drawing because the glass fiber can slide in the middle of the aluminum skin. Predict wrinkling and tearing and improving the fracture toughness limit is one of the challenges in FMLs deep drawing parts. It is clear that the forming area relies on the area between wrinkling and tearing domain, and this domain is very tight for the FMLs [21]. When FMLs are formed, there is a big interaction of the manufacturing process and FMLs composition on the producibility. This interaction between the laminate design and the manufacturing process is larger for the FMLs compared to the monolithic metallic parts. This is a result of the extra failure modes of the FML and the influence of laminate composition parameters on these failure modes [22]. The laminate composition and product shape are design-driven. For producibility, it might be necessary to change the production process, product shape, or the FMLs composition [23]. Besides, various deep drawing process parameters can prevent or delays the failure during forming, such as the punch speed, BHF, Cavity pressure, etc. This solid interaction underlies the relationship between the manufacturing method and material design. The objective of the present study is the development of a new appropriate forming method with enhanced quality, production time, and dimensional accuracy and depth, without affecting the mechanical properties. In this investigation, we propose a new laminate blank preparation using the glass fiber patches instead of a single layer. And a non-cured FMLs deep drawing followed by a Hot-pressing process. The proposed process was compared with the conventional process using both simulation and experimental results.

Section snippets

Experimental setup

The 2/1 GLARE specimens consisted of two top layers of aluminum alloy 2024-T3 (Thickness: t = 0.5 mm) and a middle layer of a plain weave E-Glass fiber (Thickness: t = 0.2 mm). The fabric is already saturated with thermosetting epoxy resin, with 35 ± 3% resin content. The Aluminum sheets are cut into a circular form with a diameter of 140 mm. The surface preparation of the aluminum sheets was done by the phosphoric acid anodizing process, which helps to rough up the aluminum surface to create a

Results and discussion

Appropriate tests were planned and performed to develop an innovative material design and forming method by analyzing the forming behavior and failure modes during the drawing process. Table 1 and Fig. 3 illustrates the experimental and simulation results using the conventional and the proposed process. In the conventional process, wrinkles occurred in the flange area due to the insufficient BHF to maintain the laminate system and stop the wrinkling Fig. 3(a). The highest wrinkling amplitude

Conclusion

In this investigation, research has been carried out on the process and material design development for the production of small complex components made of FMLs, using optimized glass fiber patches and non-cured FMLs followed by the Hot-pressing process, in the direction to enhance the FMLs forming process by eliminating defects and improving the drawing depth. The significance of this proposed process were discovered using a numerical simulation model and experiments. The following conclusions

CRediT authorship contribution statement

Hamza Blala: Conceptualization, Investigation, Methodology, Writing - original draft. Lihui Lang: Supervision, Project administration, Writing - review & editing. Lei Li: Visualization, Data curation, Software. Sergei Alexandrov: Supervision, Writing - review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was supported by the National Natural Science Foundation of China [No. 51675029], and Natural Science Foundation of Hebei Province of China [No. E2019202224].

References (24)

  • F. Schubert et al.

    Thermoplastic fiber metal laminates for automated production

    Lightweight Desg. Worldwide

    (2019)
  • T. Mennecart et al.

    Analysis of the influence of fibers on the formability of metal blanks in manufacturing processes for fiber metal laminates

    J. Manuf. Mat. Proc

    (2019)
  • Cited by (0)

    View full text