Aircraft structures made of Carbon Fiber Reinforced Composites (CFRP) are susceptible to impact damage in service. If the damage is of sufficient size, strength and service durability of the structure are degraded. The size and location of the damage are only predictable in a statistical sense; leading to excessive conservatism in design strains. Statistical approaches (1) have been explored, but condition monitoring is increasingly seen as the way forward. Smart materials are an attractive route to condition monitoring, and in the past ten years there has been considerable work to develop optic fiber strain and damage sensing techniques for composites, together with similar work on compliance change, acoustic emission and acoustic injection techniques (2). All of these involve use of discrete sensors, manufactured integral with the composite laminate. Many of the difficulties associated with use of discrete sensors may be overcome by adoption of techniques which rely on changes in the physical properties of the composite as a consequence of damage. A prime candidate is the electrical resistance technique. This relies on changes in electrical resistance, or of potential distributions in the laminate to characterize the damage state.