Microstructural Assessment of Freeze-Thaw Impact on Carbon/Glass/Epoxy Composites

Abstract

Cracks and debonded areas, nucleated by high residual stresses as a result of the changing temperature, can easily propagate at the weaker interface. The differential change in the condition of constituent phases (fibre, matrix resin and interphase) of fibrous polymer composites in freeze-thaw environments can result in a significant mismatch among constituents and this eventually leads to the evolution of localised stress and strain fields in composites. The situations could easily result in the nucleation of delaminating micro-cracks in the composites. The specimens were tested at 2, 50, 100, 200 and 500 mm/min crosshead speed to evaluate the microstructural integrity of glass, carbon and glass/carbon reinforced epoxy composites during 3-point loading at ambient, cryogenic (–50 ̊ C & –80 ̊C), fast thaw and slow thaw conditions. The SEM micrographs show changing failure behavior at different situations.