Nicalon fibre reinforced borosilicate glass composites were prepared under different processing conditions. Hot pressing parameters were changed from 900 degrees C to 1200 degrees C, to investigate the effect on the mechanical strength and interfacial properties of the composite. Bend strength was measured by a 3 point bend test arrangement. A nano indenter was used to measure the fibre-matrix interfacial shear stress, interfacial fracture energy and fibre residual stresses. X-ray diffraction analysis was employed to investigate matrix crystallisation, and transmission electron microscopy was used to analyse the fibre-matrix interface.