Failure and damage evolution of wrinkled CFRP laminates with different stacking sequences

Abstract

Out-of-plane wrinkles (OPWs) severely threaten the structural reliability of carbon fiber-reinforced polymer (CFRP) composites, whereas stacking-sequence optimization can partially mitigate their detrimental effects. A VUMAT-based numerical framework incorporating 3D Hashin failure criteria and a continuous strain-softening degradation scheme was developed to assess wrinkled CFRP laminates. The model was validated against experimental results, with a maximum relative error of 2.2% in ultimate strength prediction, and successfully captured the coupled interactions between stacking sequences and OPW geometries. At the macroscopic level, multidirectional layups exhibited lower ultimate strength but enhanced damage tolerance and more gradual failure evolution compared with unidirectional layups. Parametric analysis identified an OPW aspect ratio of 0.20 as the threshold for severe stress localization. At the microscopic level, under compressive loading, interlaminar stiffness mismatch in MD layups induced extreme localization of out-of-plane normal stress, with σ₃₃ increasing nearly 20-fold relative to the UD baseline and reaching 134.57 MPa, accompanied by elevated in-plane shear stress τ₁₂ of 25.96 MPa. These results indicate that MD layups provide effective macroscopic damage tolerance, while the revealed three-dimensional microscopic stress amplification mechanisms should be considered in precise defect-tolerance design of composite structures.