A structurally embedded fibre optic damage detection sensor for composite
materials is described. The system is designed specifically for the detection
of barely visible damage resulting from low-velocity impacts in Kevlar-epoxy
laminates. By monitoring the light transmission properties of optical fibre
embedded in the composite, it has been shown that the integrity of the material
can be accurately determined. The effect of several parameters on
the sensitivity of the system has been investigated, including the effect of
the optical fibre orientation and depth of embedding within the composite.
A novel surface treatment has also been developed for the optical fibres to
ensure they will fracture at the requisite damage level. The influence of the
optical fibre sensors on the tensile and compressive material properties and
on the impact resistance of the laminate has also been studied. Extensive
experimental results from impact tests are reported and a numerical model
of the impact event is presented which is able to predict and model the
damage mechanism and sensor system. A new and powerful method of nondestructive
evaluation for translucent composite materials based on image
enhanced backlighting is also described.Ph.D