Characterization of low-velocity impact response and damage tolerance of thermoplastic/thermoset composite laminates under strong and complex preload

Abstract

In this study, a novel uni/biaxial preload-coupling loading device is designed to systematically investigate the low-velocity impact mechanical response and the evolution of Compression After Impact (CAI) strength of thermoplastic/thermoset (TP/TS) laminates under seven typical loading boundary conditions. The influence of preload forms and clamping boundary conditions on the impact mechanical response and damage evolution of TP/TS laminates is first comparatively analyzed. The regulation mechanism of preload forms on the compressive failure behavior of laminates is elucidated through the innovative integration of three-dimensional digital image correlation (3D-DIC) and infrared thermography monitoring techniques. Through multiple regression analysis, a quantitative correlation model is established between damage characteristic parameters (such as dent depth, delamination damage projection area (DDPA), and energy dissipation) and CAI strength. Experimental results indicate that preload types and loading boundary conditions significantly affect the damage tolerance performance of laminates. Specifically, TS laminates under uniaxial compressive preload exhibit a typical “catastrophic” delamination failure mode, while TP laminates demonstrate superior damage tolerance characteristics. Furthermore, the dual-parameter evaluation model based on dent depth and DDPA overcomes the limitations of traditional single damage parameter assessments, providing a significant methodological reference for load-compatibility design and safety evaluation of composite structures in aerospace applications.