Testing for Toughness and the Development of Toughened Thermosetting Moulding Compounds

This paper is part of a project aimed at improved toughness of phenolic materials. Although some improved toughness materials are included, the main thrust of the paper concerns the methodology associated with characterising toughness. Glass fibre reinforced phenolic systems are assessed using instrumented falling weight impact (IFWI) as well as fracture mechanics measurements of toughness and strength. Agreement between the two approaches is good provided that the IFWI method measures energy to initiate a crack. It is also established that optimisation of formulation of the resin system is most sensitive when directly applied to the resin system alone. A procedure for characterising such resins is described where fracture mechanics parameters are again used to monitor toughness.