Hygrothermal aging of particle-filled epoxy-based composites

In this study hygrothermal aging in two particle-filled epoxy-based composites was investigated. The filler loading of both composites was comparable but differed in the filler type (portland cement; quartz). The influence of 10 different climates with varying humidities and temperatures on mechanical properties was examined periodically with tensile tests. The changes in structure and composition were investigated with microscopy, EDX, TGA, and XRD. Elastic properties were calculated with a Halpin-Tsai model and the tensile strength with an interface-dependent model proposed by Pukanszky. Here we suggest that physical aging and the growth of crystals within cement fillers contribute to stiffening effects. Water uptake by cement fillers also led to an increase in modulus and was ascribed to the formation of hydration products. The results indicate that the degradation of Young's modulus is not affected by the filler type, whereas the degradation of the tensile strength is substantially influenced.