Processing and characterisation of model optomechanical composites in the system sapphire fibre/borosilicate glass matrix

Optomechanical composites based on the system sapphire fibre/borosilicate glass matrix were fabricated and characterised. Different techniques of fabrication were used: composites with randomly orientated chopped sapphire fibres were produced by powder technology and pressureless sintering, whilst unidirectionally oriented fibre composites were fabricated by hot-pressing as well as by sandwiching glass slides and arrays of parallel fibres followed by heat-treatment. Pressureless sintered samples were poorly densified and were opaque. Hot-pressed and “sandwich structure” composites were dense and exhibited strong interfaces between fibres and matrix. Only the “sandwich structure” composites were transparent and showed significant light transmittance in the visible wavelength range, only 20% lower than that of the unreinforced matrix. Due to the strong matrix/fibre interface limited fibre pull-out during composite fracture was observed. The fabricated transparent composites represent an improved version of the traditional material wired glass. They are candidate materials for applications in high performance fire and impact resistant windows requiring high impact strength and avoidance of fragmentation upon fracture.