High-frequency dielectric spectroscopy as NDE technique for adhesively bonded composites structures

Abstract

This paper discusses the application of high-frequency non-destructive techniques to the ageing study of carbon fibre reinforced plastics (CFRP) adhesively bonded composite structures. The effect of changes in the surface alignment and subsequent bulk orientation of carbon fibres on the dielectric propagation has been investigated. The ingress of moisture in the raw materials and in the joint structure is presented. The high-frequency time domain response (TDR) analysis allows the integrity of the structure to be explored and a good correlation is shown between TDR analysis and gravimetric results. This study indicates that the application of high frequency dielectric measurements is applicable to CFRP bonded structures. The dielectric study not only indicates a new way to assess the state of such a structure but is also producing new insights into the application of TDR measurement to non-isotropic materials.