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Impact events on composite structures that may cause damage can be readily detected and located using sensors that respond to the resulting impact stress waves as they propagate. This capability can be used as an alert to maintainers or operators who use the structures that an incident has occurred. However, for this capability to be truly useful it must include the capacity to determine automatically if the impact has caused damage. This will avoid the situation where a follow up inspection of the impact site reveals that no damage has been caused (no-fault found). This paper reports results from impact tests on glass and carbon composite, structural test specimens in which impact sensor data has been processed to reveal clear features that allow discrimination between damaging and non-damaging impacts.

A structural damage detection system has been used to sense the propagation of cracks in a metallic flight test specimen on board a Hawk jet trainer. The work has demonstrated that the growth of structural cracks can be successfully and automatically detected on board a fast jet while flying unrestricted flight profiles. The experiment was part of a European collaborative defense program designed to demonstrate a number of diverse structural health monitoring technologies during flight in a military jet environment. This paper focuses on the performance of an acoustic emission detection system that was able to detect the growth of cracks in an alloy cantilever specimen bolted to a structural bulkhead in a pod suspended beneath the aircraft's left hand wing.