Interaction between optical fibre sensors and matrix cracks in cross-ply GRP laminates—part 1: passive optical fibres

The obtrusivity of a passive optical fibre embedded in the 0° ply of a model cross-ply GRP laminate has been investigated experimentally and theoretically. The experimental results show that for quasi-static loading and cyclic loads with a peak strain greater than the quasi-static cracking threshold, both the initiation and development of matrix cracks are insensitive to the presence of the optical fibre. However, for cyclic loading with a peak strain just below the cracking threshold, the matrix crack-growth rate is reduced significantly in the vicinity of the optical fibre. The reduction in the crack-growth rate can be understood in terms of a reduction in the strain-energy release rate for cracking as a consequence of the local stiffening of the 0° ply due to the presence of the optical fibre.