The role of the resin matrix/hardener ratio on the mechanical properties of low volume fraction epoxy composites

The mechanical performance of composite materials is usually associated with the properties of their reinforcement. However the matrix materials also play an important role as is the case for thermoset resin matrix composites which can be designed for specific applications by properly changing the polymer used as matrix. The mechanical, physical and chemical properties of the polymer matrix can be tailored by changing the processing conditions and the type and amount of the chemical substance used as hardener. In this work an investigation was carried out on the variation of the mechanical properties of two composites of large commercial applications as a function of the resin matrix formulation. The mechanical properties of the matrix where modified by varying the amount of hardener Experimental results showed that it is possible to considerably vary the performance of low volume fraction composites by the proper processing of the matrix. In particular, it was observed that a significant change on the deformability of the composites can be obtained. Micromechanics equations were used to explain the experimental trends observed.