Abstract: In order to improve the ductility of ultra-thin carbon fiber composites unidirectional laminates (UDLs), both CF/UHMWPE hybrid and ultra-thin carbon fiber UDLs with the same thickness were prepared. Their mechanical properties were tested, and the micro-morphology of the specimens was observed after tensile fracture in this paper. The results show that the average tensile strength of CF/UHMWPE hybrid UDL reaches 1 695 MPa, and the UDL presents a capacity withstanding 1 560 MPa load for 10 s after tensile damage occurred. Compared to ultra-thin carbon fiber laminates, although the average tensile strength of the hybrid UDLs is reduced by 11.6%, their average elongation is increased by 7.1%. The hybrid specimens do not develop brittle fracture damage during tensile testing, and the splitting phenomenon of the UDLs under macroscopic morphology is reduced. The decrease in tensile strength of the hybrid UDL is related to the lower volume fraction of carbon fibers, but the UHMWPE fibers, which were used as the inserted phase, increased the elongation of the hybrid UDL because of its good ductility. Microstructurally, the inserted ultra-thin UHMWPE fiber layer inhibits the generation and expansion of the cracks in the UDL and suppresses the brittle fracture of the adjacent carbon fiber layers, which improves the overall ductility of the hybrid UDL. The experimental results provide the basis for designing highly ductile hybrid composites further.

Key words: ultra-thin UHMWPE fiber intercalation, carbon fiber laminates, interlayer mixing, tensile properties, fracture morphology, composites