About the impact behavior of woven-ply carbon fiber-reinforced thermoplastic- and thermosetting-composites: A comparative study

Abstract

This study is aimed at comparing the response of TS-based (epoxy) and TP-based (PPS or PEEK) laminates subjected to low velocity impacts. C-scan inspections showed that impact led to diamond-shaped damage resulting from different failure mechanisms: fiber breakages in warp and weft directions, more or less inter-laminar and intra-ply damage, and extensive delamination in C/PEEK and C/epoxy laminates. The permanent indentation can be ascribed to specific mechanisms which mainly depend on many factors including the ultimate out-of-plane shear strength, and the interlaminar fracture toughness in modes I-II-III. In TP-based laminates, the matrix plasticization seems to play an important role in matrix-rich areas by locally promoting permanent deformations. Fiber-bridging also prevents the plies from opening in mode I, and slows down the propagation of interlaminar and intralaminar cracks in modes II-III. Both mechanisms seem to reduce the extension of damages, in particular, the subsequent delamination for a given impact energy. In epoxy-based laminates, the debris of broken fibers and matrix get stuck in the cracks and the adjacent layers, and create a sort of blocking system that prevents the cracks and delamination from closing after impact.

Impact damage and CAI strength of a woven CFRP material with fire retardant properties

“…Many authors have addressed the issue of assessing and even enhancing the fracture toughness response to impact loading and the subsequent resistance to CAI. For example by using different matrix thermosetting or thermoplastic materials [23] or by applying veils which are other layered materials within the laminates [24,25] or even by applying metallic materials in the form of titanium pins in the transverse direction [26].…”

Effect of reinforcement material on impact properties of epoxy

“…However, matrix cracks tips may act as onset sites for delamination and fiber breakage which do change the local stiffness of laminates [10]. In addition, the specimen can absorb the impact energy by other means including indentation (representative of local matrix crushing and local fiber breakage), delamination, splitting or fibers peeling on the non-impacted side [11]. For all composites the onset of the first damage can be observed before 2 ms, except for epoxy its start after 2ms.…”

The influence of toughening-particles in CFRPs on low velocity impact damage resistance performance

“…fibre-free monolithic samples) do not usually translate to equivalent improvements in composite intralaminar toughness [16][17][18]. This has been linked to the effective scale of the crack-tip process zone; in composite materials the interply region is constrained by the fibres, and the thickness of this region is usually much less than that of the process zone seen in bulk material [19,20].…”