Evaluation of burst strength of FW-FRP composite pipes after impact using pitch-based low-modulus carbon fiber

In order to improve the burst strength after impact of the filament-wound carbon fiber reinforced plastics (FW-CFRP) composite pipes, three types of the low-modulus pitch-based carbon fiber with high-compressive failure strain were applied to the surface of the FW-CFRP composite pipes. Impact tests with impactor radius of 3, 10, 20 mm were conducted on the specimens. Cross-sectional observation were conducted to evaluate the impact damage, such as fiber microbuckling and delamination. Fiber breakages caused by microbuckling were suppressed in the specimen with the low-modulus pitch-based carbon fiber. Internal pressure tests were conducted on the specimen after impact tests. The burst strength of the FW-CFRP composite pipes after impact was observed to decrease with increasing effective damage depth, which is defined as fiber breakage depth divided by the thickness of the CFRP. Consequently, it is clarified that the residual burst strength was enhanced with the application of the low-modulus pitch-based carbon fiber.