THERMAL SHRINKAGE-INDUCED COMPRESSIVE FRAGMENTATION IN COMPOSITE-MATERIALS

Compressive thermal stresses in microcomposites-viewed by polarised li ght microscopy-produce a typical stress pattern comprising a regular s eries of fringes along the fibres. Our recent studies have regarded th at stress pattern indicative of a continuous fibre fragmentation proce ss and have used it to measure the compressive strength of the fibre a nd the fibre/matrix interfacial strength. In this study the nature of the compressive fragmentation process is examined by a matrix dissolut ion procedure proposed recently in the literature. It is found that st ress fringes are indeed indicative of fibre breaks but, in addition, t hey also reflect skin failure by shear deformation and microbuckling a nd, most importantly, they even reflect reversible microbuckling. Sinc e the reversible microbuckling occurs at a stress level which is just below the compressive strength of the fibre, it is suggested that this marks the onset of its compressive failure.