Influences of Hygrothermal Aging on Low‐Velocity Impact Damage Characteristics of Carbon Fiber Reinforced Composite Laminates: An Experimental and Numerical Study

ABSTRACT It is of great significance to investigate the influences of hygrothermally aging on the low‐velocity impact (LVI) response of carbon fiber reinforced polymer (CFRP) laminates in railway vehicle design. However, existing studies are still insufficient. In this study, CFRP laminates with stacking sequences of [(0/90)] 20 and [(±45)/(0/90)] 5S were fabricated and hygrothermally aged. LVI tests were performed at impact energy levels of 18, 27, and 36 J. Impact damage was characterized through optical inspection and phased array ultrasonic testing (PAUT). A progressive damage model incorporating hygrothermal effects was established. The experimental results demonstrate that hygrothermal aging had a negligible impact on the force‐displacement curve and surface failure, but significantly degrades the impact resistance. At an impact energy of 36 J, the peak contact force decreased by 9% and 5% for the [(0/90)] 20 and [(±45)/(0/90)] 5S laminates, respectively, whereas the corresponding maximum displacements increased by 14% and 4%. Compared to unaged specimens, aged specimens exhibited significantly larger surface crack dimensions. Numerical simulation results further confirmed this trend, indicating a 34% increase in the average delamination area for the aged [(±45)/(0/90)] 5S laminate under 36 J impact.