Micro-mechanical investigation of glass fibre/resin interface failure in mode I and mode II

Fibre reinforced composites are experiencing a period of consistent and significant growth which is predicted to continue, due to the sustained global increase in demand across a number of industrial sectors. One of the critical elements in the success of such composites in both the short and longer term is the interface/interphase between reinforcement fibres and matrix. Poor adhesion will generally lead to composites with insufficient mechanical performance. Degradation of the interface/interphase region during service life will lead to a decrease in performance, eventually to a point where the part can no longer fulfil its intended function. Micro-mechanical test methods can be an advantageous approach to analysing the fibre-matrix interface as they reduce material consumption and simplify the analysis compared with composites. In this paper some of the disadvantages of the commonly used microbond test are discussed, particularly difficulties related to testing of vinyl esters. A new micro-mechanical interface test is introduced which induces failure at the interface in mode I as opposed to the shear failure that occurs with microbond and several other contemporary interface tests.