Effects of Stacking Configuration on Flexural Degradation of CFRP Laminates Under Hygrothermal and Salt Spray Environments

The effects of stacking configuration on the environmental durability of carbon fiber-reinforced polymer (CFRP) laminates were investigated under hygrothermal and salt spray aging. Unidirectional [0]n and cross-ply [0/90]n laminates were aged for up to 42 d, and their moisture absorption, chemical structure, dynamic mechanical behavior, flexural properties, and fracture characteristics were evaluated. Hygrothermal exposure produced higher moisture uptake and diffusion rates than salt spray, while the Langmuir model described the absorption behavior more accurately than the Fick model. After 42 d, the glass transition temperatures of the [0]n and [0/90]n laminates decreased by 23.8% and 23.7% under hygrothermal aging compared with 9.0% and 6.9% under salt spray. The corresponding flexural-strength losses were 16.1% and 18.6% versus 9.6% and 10.7%. Although the [0/90]n laminate exhibited slightly lower moisture uptake, it suffered greater strength degradation because transverse cracking in the 90° plies promoted interfacial debonding and delamination. These results show that the environment governs degradation intensity, whereas stacking configuration controls damage propagation and flexural failure.