Effect of Thermal Cycling on Hardness and Impact Properties of Polymer Composites Reinforced by Basalt and Carbon Fibers

The polymer-matrix composites may be significantly affected by cyclic temperature changes. This study investigates the effects of thermal cycles on hardness and impact resistance of three types of phenolic-matrix composites, that is, phenolic resin reinforced with (1) woven basalt fibers, (2) woven carbon fibers and (3) hybrid of basalt and carbon fibers. The effect of thermal cycling on hardness and impact resistance was material-dependent. While, the thermal cycling rapidly decreased the hardness of composites reinforced by carbon fibers, it gradually decreased the hardness of composites reinforced by basalt fibers. While, the Charpy impact energy of carbon/phenolic (CFP) and basalt/carbon/phenolic (BCFP) composites was not significantly affected by thermal cycles, the Charpy impact energy of basalt/phenolic (BFP) composites shows a sharp decline with increasing thermal cycling, and reaches a plateau after a certain cycle. Based on the results, the BFP composites was significantly harder than CFP and the composites containing carbon fibers in spite of demonstration of low impact resistance at primal cycles, possessed very gradual decline in impact resistance compared to BFP composites after the thermal cycling.