Mechanical performance of hybrid thermoset composites: Effects of matrix and reinforcement hybridization

Hybrid epoxy/vinyl ester (EP/VE) and epoxy/unsaturated polyester (EP/UP) resins were used as matrices to prepare unidirectional carbon fibre (CF) and carbon/glass fibre (CF/GF) reinforced composites targeting toughness of improvement. Hybrid resins were produced simultaneously (one-pot) and sequentially. (Thermo)mechanical properties of hybrid resins were determined in surface hardness, three-point bending, dynamic mechanical analysis (DMA), and differential scanning calorimetry (DSC) tests. Hybrid matrix composites with CF and CF/GF hybrid reinforcements were characterized with quasi-static mechanical (three-point bending) tests performed in 0° (longitudinal) and 90° (transverse) directions. In addition, flexural fatigue tests were run on UD composites. Interlaminar properties were deduced from in-plane shear strength (IPSS) test and fractographic inspection in a scanning electron microscope. The EP/VE hybrid resin exhibited improved energy absorption compared to neat constituent resins in contrast to EP/UP. Using hybrid resins as matrix highly improved the toughness and durability of the corresponding composites. Improved energy absorption was attributed to the phase structure of the hybrid resins, which also positively affected the IPSS.