Delamination propagation manipulation of composite laminates under low-velocity impact and residual compressive strength evaluation

The poor delamination resistance of laminated composites is always regarded as a potential threat to the service safety of the primary load-bearing structure. However, delamination is inevitable during low-velocity impact (LVI) events, as a result, the residual compressive strength of laminates is significantly reduced. Discrete interleaving is a novel strategy to enhance the damage tolerance of these composites, yet the damage mechanism of laminates modified by this method is more complicated. In this paper, we investigated the delamination failure mechanism of quasiisotropic laminates through thermal deply experiment, and proposed a discrete interleaving scheme based on its damage characteristics. Accordingly, a series of LVI and compression-afterimpact (CAI) tests were conducted to validate the design philosophy. Besides, the damage constitutive relation and evolution model applicable to discrete interleaved laminates were explored in detail, a numerical model embedded strain-rate-dependent progressive damage criterion and modified cohesive zone model was established to further study the damage mechanism. Experimental and numerical results exhibit excellent alignment. The results demonstrate that the CAI strength is enhanced by 16.48 % according to the proposed discrete interleaving method. The main reason is attributed to the employed method can manipulate the delamination propagation during the low-velocity impact loading, and then maneuver the compressive failure mode of laminates to achieve a favorable benign failure (implying higher CAI strength).