CHARACTERIZATION OF THE FIBRE MATRIX INTERFACE IN REINFORCED POLYMERSBY THE PUSH-IN TECHNIQUE/

The push-in test is the only micromechanical rest method that is not r estricted to artificial fibre/matrix arrangements, but allows the in s itu characterisation of interfaces in composites fabricated and stress ed under realistic conditions. However, with the application of this m ethod to reinforced polymers some problems ar ise both in the mathemat ical model for evaluating test data and in the practical performance o f the test. Because in some cases the deformation of the relatively co mpliant polymeric matrices cannot be neglected an extension of the exi sting model is required. For this purpose, the elastic energy of the m aterial around the debonded part of the fibre is estimated and include d in the energy-balance analysis. Because of the small diameter of the fibres usually used for reinforcing polymers, a test apparatus was de signed which ensures a high positioning accuracy in the xy plane as we ll as in the z direction. In order to minimise thermal and mechanical influences, the microscope for fibre selection and the force sensor/in denter are directly connected together and the apparatus is designed t o be stiff in all components. A solid-state bending joint guarantees v ery precise control of the axial movement. Three examples of the appli cation of this easy-to-handle and low-cost test apparatus are presente d briefly in the paper: assess fibre/matrix combinations, measures to improve the interfacial adhesion and the influence of water on the int erface. (C) 1997 Elsevier Science Limited.