Investigating the effects of UV light and moisture ingression on low-impact resistance of three different carbon fiber–reinforced composites

Abstract

In this article, the effects of ultraviolet light (UV) and moisture exposure on the low-velocity impact behavior of three different carbon fiber (CF) laminate composites (unidirectional fibers, plain weave woven fibers, and non-crimp fibers (NCF)) are reported based on the experimental observations. The composite laminate was fabricated by vacuum bagging method following the manufacturing specifications with symmetric and asymmetric stacking, and then the test coupons were extracted for impact testing, C-scan, and surface characterization studies before and after UV light and moisture exposures. A low-velocity impact test was carried out to evaluate the damage resistance and tolerance of the laminate specimens. The test outcomes uncovered that the NCF laminates were far predominant in load-carrying capacity than the woven and unidirectional laminates, with the NCF-asymmetric (NCF-NS) laminate exhibiting the greater load-carrying capacity of 3017.7 kN/m and impact energy of 7.07 kJ/m (NCF-NS). The NCF-symmetric (NCF-S) laminate showing impact energy of 7.0 kJ/m and load-carrying capacity of 2886.8 kN/m with some decrease after UV and moisture exposure for both cases. The ultrasonic C-scan revealed that NCF laminates, both NCF-S and NCF-NS, have the least penetration indicating greater out of plane fracture toughness and damage tolerance. The NCF-NS laminate has the least damage area (33.35 mm2) and dent depth (0.12 mm) as compared with other laminate studied here. The wettability of the panels was similar; however, the woven (baseline) panel showed the highest water contact angle (112°). After the UV and salt fog exposure, the contact angles of the composite panels were reduced between 66° and 58°. In addition, this study also reveals the effect of stacking sequence on the impact properties of the NCF composite laminate.