Compressive thermal stresses in microcomposites-viewed by polarised light microscopy-produce a typical stress pattern comprising a regular series of fringes along the fibres. Our recent studies have regarded that stress pattern indicative of a continuous fibre fragmentation process and have used it to measure the compressive strength of the fibre and the fibre/matrix interfacial strength. In this study the nature of the compressive fragmentation process is examined by a matrix dissolution procedure proposed recently in the literature. It is found that stress fringes are indeed indicative of fibre breaks but, in addition, they also reflect skin failure by shear deformation and microbuckling and, most importantly, they even reflect reversible microbuckling. Since 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.