Abstract:
This Thesis investigates the damage sensing capabilities of the electrical potential
measurement technique in carbon fibre reinforced polymer composites.
Impact damage was introduced in multidirectional laminates and its effect on potential
distribution studied. It was found that delaminations and fibre breakages within the
laminate can be detected and located by measuring potential changes on the external
composite surface. The extent and size of potential changes were significantly affected by
the position of the current electrodes in relation to the potential measurement probes.
A numerical model was developed investigating the effect of different size delaminations,
located in various positions within the lamina, on electrical potential distributions on the
external ply, and a quantitative analysis of the numerical results is presented. The
numerical simulations demonstrated that the measured potential changes on the external
ply were in proportion to the delamination size. The numerical and experimental results
were compared and the optimum configuration of current electrodes and potential probes
for damage detection selected.
The response of electrical potential to mechanical strain, in unidirectional and
multidirectional samples was also investigated. It was found that the conductive medium,
used for introducing the current, defines the piezo-resistance performance of the
composite. A finite element model was developed able to predict the effect of
inhomogeneous current introduction in unidirectional specimens on electrical potential
and piezo-resistance. The effects of temperature and water absorption on potential
measurements were also presented.
