A Numerical Study on Lightning Damages and Residual Strength of CFRP Laminates Considering Delamination Induced by Thermal Stress

Most numerical studies on carbon fiber-reinforced polymer (CFRP) lightning damages fail to account for delamination, a factor that plays a significant role in the subsequent analysis of residual strength. This study establishes an electro-thermo-mechanical coupled numerical model incorporating delamination effects to predict lightning-induced damage in carbon fiber-reinforced plastic (CFRP) composites. Subsequently, parametric investigations evaluate the influence of varying input loads and stacking sequences on interlaminar pyrolysis and delamination damage, with damage assessment quantitatively conducted based on simulated post-strike uniaxial ultimate compressive loads. Post-strike uniaxial compressive strength reduction with cohesive elements is 28.91%, demonstrating closer alignment with experimental reduction (36.72%) than the 21.12% reduction predicted by the interlaminar-effect-neglecting model. Under combined thermal expansion and shockwave overpressure, the 28.91% compressive strength reduction demonstrates closer alignment with the experimental 36.72% reduction than the 25.13% reduction observed under isolated shockwave overpressure. The results highlight the critical role of thermal delamination in compressive strength reduction, with distinct waveform-dependent mechanisms: under C-waveform lightning currents, arc thermal effects cannot be neglected; D-waveform strikes exhibit predominant contributions from impact loading to delamination damage, with thermally driven delamination likewise pronounced. Increased current amplitude correlates with amplified mechanical damage severity, while premature symmetry in ply stacking sequences exacerbates compressive performance degradation. This work enhances multi-physics modeling fidelity by bridging thermal delamination and mechanical degradation pathways, offering foundational insights for optimizing lightning strike resistance in advanced aerospace composite systems.