Damage mechanism and residual tensile strength of CFRP laminates subjected to continuous laser irradiation

The performance of carbon fiber reinforced polymer (CFRP) laminates can be significantly degraded by high-energy laser irradiation, which induces damage mechanisms fundamentally different from those caused by conventional mechanical defects. In this study, the damage behavior and residual tensile strength of CFRP laminates subjected to continuous-wave laser irradiation were investigated through laser perforation experiments and open-hole tensile tests, using conventionally drilled open-hole laminates as the reference. Multiscale damage morphologies were characterized, and a sequentially coupled thermo-mechanical finite element model was developed to analyze stress redistribution and progressive damage evolution. The results indicate that laser irradiation produces a conical ablation crater surrounded by a pronounced heat-affected zone (HAZ), which is characterized by resin pyrolysis, carbonization, fiber exposure, cracking, and interlaminar delamination. Compared with drilled specimens, laser-ablated specimens exhibit a significant reduction in residual tensile strength of 50%-68%, with earlier damage initiation and a distinct first load drop, indicating a progressive failure process dominated by HAZ-induced degradation. Increasing laser power density reduces the penetration time and suppresses HAZ development, leading to a partial recovery of residual tensile strength. In a representative case, an improvement of approximately 88% was achieved as laser power increased from 1200 W to 2400 W at a spot diameter of 4 mm. Numerical results further demonstrate that the coupled effects of HAZ-related material degradation and ablation-induced geometric discontinuities fundamentally alter stress transfer paths and damage evolution mechanisms, providing a mechanistic basis for laser-induced damage tolerance assessment of CFRP structures.