Low-velocity impact and compression-after-impact behaviors of carbon/glass fiber hybrid composite laminates based on thin-ply carbon fiber prepreg and unidirectionally arrayed chopped strand

Abstract

The impact resistance is one of the most important mechanical properties of lightweight fiber-reinforced polymer composites (FRPs), which directly affects its application in engineering fields. However, due to the inherent brittleness of fibers, the mutual exclusion of strength and toughness has become one of the bottlenecks in FRP design. Considering the effect of hybrid structure and short fiber on improving the pseudo-ductility of FRP laminates, in this study, short fiber structures were prepared by introducing discontinuous slits into the thin-ply carbon fiber prepregs and mixing with glass fiber prepregs to fabricate carbon/glass fiber hybrid laminates (C/G). Low-velocity impact (LVI) tests and compression-after-impact (CAI) tests were carried out at energy levels of 15 J, 20 J, 25 J, and 30 J. The full-field displacement of specimens during CAI was captured by three-dimensional digital image correlation (3D-DIC). In addition, how the damage morphology varies spatially due to the different deformation and damage modes is learned from X-ray micro-computed tomography (Micro-CT) techniques. The experimental results indicate that the S2-UACS specimen exhibits the most outstanding impact resistance. Based on the visualization characteristics of C/G hybrid laminates, it is observed that the delamination on the backside of the C/G hybrid laminates is improved by introducing discontinuous slits. The degree of LVI damage significantly affects the CAI damage tolerance of the laminates. After impact at energies from 15 to 30 J, the CAI strengths of the C/G hybrid laminates with the discontinuous fiber structure are 9.94 %, 25.61 %, 10.29 %, and 11.69 % higher, respectively, than those of the continuous carbon fiber laminates. Furthermore, micro-CT revealed that the introduction of slits restrains the occurrence of fiber buckling and delamination propagation in C/G hybrid laminates during the CAI test.