Effects of Fiber Orientation, Thermal Post-Curing, and Corrosive Environment on the Mechanical Properties of CFRP Laminates.

Carbon fiber-reinforced polymer (CFRP) composites are widely used in engineering applications due to their high strength-to-weight ratio and corrosion resistance. However, their mechanical performance depends strongly on laminate architecture, processing conditions, and environmental exposure. This study investigates the effects of fiber orientation, thermal post-curing, and corrosive SO2 atmosphere on the mechanical properties of CFRP laminates. Three-layer carbon/epoxy laminates with 90°, 45°, and [90°/45°/90°] fiber orientations were manufactured by vacuum-assisted lamination. Selected specimens were post-cured at 80 °C for 10 h and exposed to sulfur dioxide according to ISO 3231. Tensile and Charpy impact tests showed that the 90° laminate exhibited the highest tensile strength (484 MPa), whereas the 45° laminate showed the lowest value due to shear-dominated load transfer. Post-curing increased tensile strength by approximately 10-30%, while exposure to the corrosive environment reduced both tensile strength and impact toughness. The observed behavior was associated with differences in load-transfer mechanism, possible increased degree of cure and/or residual stress relaxation after post-curing, and degradation of the epoxy-matrix and fiber-matrix interface after SO2 exposure. The results demonstrate that suitable selection of laminate architecture and thermal treatment can significantly improve the durability of CFRP structures intended for aggressive environments.