Mechanical properties and fracture behaviors of epoxy composites with multi-scale rubber particles

In this work, we developed a strategy to balance the toughness and thermal resistance of epoxy composites by incorporating the multi-scale rubber particles. Two types of rubber i.e. the phase-separation-formed submicron liquid rubber (LR) and preformed nano-scale powered rubber (PR) particles were chosen as tougheners. It was found that the combination of these multi-scale rubber particles not only provides superior efficiency in enhancing the impact resistance of epoxy composites, but also results in balanced glass transition temperature. In particular, the highest gain in impact strength was obtained for the ternary composites containing 9.2 wt% submicron liquid rubber and 9.2 wt% nano-sized powered rubber which were similar to 112% higher than the maximum enhancements of similar to 49% and similar to 66% for the corresponding binary composite systems with the single-phase rubber, respectively. The damage zone observation and fracture surface analysis suggested that the combined use of multi-scale particles was effective to promote matrix plastic deformation including void growth and shear banding induced by the improved rubber cavitation/debonding, which is likely responsible for the highly improved impact resistance of the ternary composites. (c) 2013 Elsevier B.V. All rights reserved.