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Currently, it is important to manufacture fiber‐reinforced epoxy matrix composites with high impact resistance besides their high strength and modulus values for industries such as automotive, aerospace, and aviation due to the brittle structure of epoxy. In this regard, we found the attractive results of the 0.5 wt% poly(vinyl butyral) (PVB)‐containing epoxy blend in terms of strength, Young's modulus, and impact resistance. These results substantially motivated us to manufacture fiber‐reinforced advanced epoxy/PVB matrix composites with 30–60 vol% carbon‐aramid fiber ratios. Flexural (three‐point bending) and tensile tests were performed to obtain strength and modulus values by measuring the force required to break the fiber‐reinforced composite specimens and elongation at break points. Interlaminar shear strength tests were performed by the short beam bending method by measuring the resistance of the composite to delamination. The Charpy impact test was used to measure the energy absorbed during crack formation and fracture propagation. The composites with PVB were generally superior to those without PVB (EPCs). Two types of findings were observed. First, PVB increased the tensile and flexural strength values substantially for the 30 and 40 vol% ratios, but the modulus values slightly decreased. Second, PVB also substantially increased the modulus values for the 50 vol% ratio besides the strength values. It was thought that this result could be attributed to the increase in the compatibility of the fiber/matrix for the 50 vol% ratio. These decreases for EPCs could be derived from the micro‐cracks and weaker interface between fiber and matrix. [ABSTRACT FROM AUTHOR]

The tensile failure mechanism of carbon–aramid hybrid fibers/epoxy sandwich structure laminates was investigated by using experimental and finite element methods. Double curing agents, triarylsulfonium hexafluoroantimonates and triethylene tetramine with a mass ratio of 4:15 were introduced into the laminates. Sandwich structure laminates, with different proportions of hybrid fibers, were cured by UV-initiated anion/cationic dual curing technique. The results showed that the synergetic curing effects of two curing agents were observed under UV irradiation, leading to the better curing of the system, which further plays a positive influence on the mechanical performance. The tensile properties and failure mechanism of the laminates depended on the stacking sequence and fiber volume fractions of the layer structures. The interplay hybrid laminates, containing three alternate plies with fiber contents of 67.7 vol%, presented the optimal tensile performance, and its tensile strength and modulus were 0.82 GPa and 22.09 GPa, respectively. The fracture morphologies revealed that pull-out and debonding of fibers were the main failure mechanism of hybrid laminates. The performance of sandwich structure laminates was determined by the load-carrying capacity of carbon fiber and load-transferring capacity of the aramid fiber and adhesive. The finite element model based on experiments was established to simulate the stress state and failure mechanism of sandwich laminates. The results demonstrated that the stress was better transferred into carbon fibers from the aramid fibers and adhesive, and the relative error rate of maximum stress from finite element analysis and experimental results was less than 5%, which were in reasonable agreement with the experimental results. [ABSTRACT FROM AUTHOR]