Compressive Failure Mechanisms of NCF Laminates with Double-Hole Defects

Compression tests were carried out on non-crimp fabric (NCF) laminates with varied open-hole orientation (angle to the loading direction) and inter-hole spacing, and the failure modes were documented by scanning electron microscopy (SEM) while the strength was quantified. Finite-element simulations in Abaqus were developed to replicate the tests, establishing a progressive-damage model for open-hole laminates under compression. Intralaminar failure was described using the 3D Hashin and a modified Puck criterion, and interlaminar delamination was modeled with cohesive elements, enabling the simulation of damage initiation, growth, delamination, and final collapse. The results show that hole orientation and spacing have a pronounced effect on open-hole compression (OHC) strength—with a spacing threshold beyond which additional spacing brings little benefit—whereas the elastic-stage stiffness is essentially insensitive to spacing and orientation. The combined intralaminar (Hashin/Puck) and interlaminar (cohesive-zone) model reproduces the characteristic three-stage response—linear, softening, and post-peak degradation—in good agreement with the experiments.