The increasing use of polymer matrix composites in safety critical applications highlights the need for reliable damage assessment techniques for these materials. One class of techniques involves the use of self-sensing elements to detect either mechanical damage or chemical degradation. Glass fibre reinforcements could potentially act as the sensing element, for at least of the former of these applications. However, conventional reinforcing fibres (e.g. E-glass) have refractive indices that are either similar to, or below that of the epoxy matrix (typically RI~1.6 in the visible), thus preventing light guiding in the fibres. We have, therefore, investigated two classes of glasses with high RI as sensing elements - germanium antimony lead sulphide glasses and silicate glasses modified with niobium. The former have the advantage of good infra-red (IR) transmission and RI values >2 in the IR regime and have been shown to work as chemical sensing elements using fibre evanescent wave spectroscopy. The RI values of the latter vary with composition but in the best case are ~1.7 in the visible regime; these glasses are also more compatible with existing reinforcing fibres and we are currently undertaking a more extended study of these niobium silicate glasses. The optical, mechanical and durability properties of the glasses developed have been assessed and reported. Their use as sensing elements will also be considered.
