Static and dynamic testing of a quasi-isotropic composite with embedded optical fibres

An efficient use of composite materials in loaded structures requires NDT techniques that can reliably monitor the damage state of these materials in situ and continuously during service. A promising solution to this problem is the incorporation of optical fibres into the composite structure during manufacture. However, because optical fibres are always an order of magnitude bigger than material fibres, stress concentrations will inevitably be created which can lead to premature damage initiation and thus to a reduction in the mechanical properties. Therefore the first step in the development of a damage detection system based on optical fibre technology always has to be an investigation of the mechanical properties of the resulting structures. In this paper, optical fibres were incorporated in the different interfaces of a quasi-isotropic composite laminate. Both static and dynamic mechanical tests were carried out to determine the influence of the optical fibres on the mechanical properties of the resulting composite structures. Differences in behaviour between the different configurations were correlated with differences in damage propagation.