Low-velocity impact properties and failure mechanism of carbon fiber-UHMWPE fiber hybrid reinforced epoxy resin composites

Carbon fiber/epoxy matrix composite laminates are widely used in aerospace automobile and other fields. It is inevitable to encounter low-speed impact events (falling of tools during production and use) in use, resulting in potential safety hazards. Delamination damage is the main damage form after low-speed impact, which will seriously affect the strength and service life of composite laminates. In order to improve its impact resistance, the toughness effect of ultra-high molecular weight polyethylene (UHMWPE) short fiber on the low-velocity impact behavior of composite laminates was studied. Both toughness fiber number and position were investigated. The results show that the maximum load and absorbed energy of composite laminates with 6 short fiber layers increase from 3.19 kN to 4.86 kN and 18.27 J to 28.89 J, ultimately increasing by 52.3% and 58.12% than the virgin laminates, respectively. The residual strength (164.73 MPa) of the modified composite laminates with 2 layers is the highest, which is 95% higher than the original laminates. Both impact damage resistance and delamination resistance of the modified composites are improved, while the dent depths after impact decrease. The toughening mechanism is that the surface energy of the fracture surface increases, and the impact pulls out some fibers, resulting in fiber bridging phenomenon. The pulled out fibers will reduce the stress concentration at the front of delamination, increase the resistance of delamination propagation, make the delamination failure consume more energy in the propagation process, and effectively hinder the propagation of crack. © 2022 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.