Effect of slit size on low‐velocity impact behavior of composite laminates with regularly arrayed chopped strands: Experimental and numerical analysis

Short fiber reinforced polymers (SFRP) based on unidirectionally arrayed chopped strands (UACS) offer exceptional formability and great mechanical properties. To ensure its stability and safety in applications, it is crucial to enhance the impact performance of UACS laminates. This study investigated the low‐velocity impact (LVI) responses and damage evolution of UACS laminates with different slit sizes and continuous carbon fiber reinforced polymer (CFRP) laminates under various impact energies (4, 7, and 11 J). The curves of force and energy were recorded during LVI tests, and the post‐impact damage area was detected by the ultrasonic C‐scan technique. Moreover, a user‐defined subroutine VUMAT, containing a progressive damage model and a Johnson‐Cook constitutive model, was written to mimic the damage evolution. Based on experiments and numerical prediction, it was found that when the size was reduced from 25 to 5 mm, the vertical slits had the effect of suppressing delamination and could restrain the propagation of delamination, which explains the distinct difference in delamination area. Highlights The effect of slit size on the impact behavior of UACS laminate was revealed. The damage mechanism was simulated with a progressive damage model. The novel UACS laminate exhibits excellent energy absorption capacity. The resistance of the slits greatly suppresses the delamination behavior. Absorbed energy and delamination area of CFRP and UACS composite laminates.