Effects of the hygrothermal aging history on epoxy resins and GFRP composites

Abstract

As the success of fiber reinforced polymers (FRP) has reached a wide range of industries, sustainability, reliability, and durability are increasingly important requirements. Complex processes occur in the polymeric matrices and the multiscale composites, especially under challenging conditions (humidity, water, temperature). Due to the variety of available constituents (fibers, sizings, resins) and the high time pressure for new products and innovations, long-term property predictions rely mostly on accelerated aging procedures. However, since the available materials can differ considerably in their characteristics, aging effects need to be understood better. Therefore, long-term studies on four epoxies demonstrate the importance of the hygrothermal aging temperature affecting their thermo-mechanical properties by plasticization and physical aging processes. Additional investigations on several glass fiber composites under the same aging conditions reveal that the matrix and interphase dominated properties are likely to develop differently from neat epoxy. The sizing durability is essential here.