Measurement of impact force for triboluminescent-enhanced composites by modified impulse method

Barely visible impact damage in composites can result in hidden damage such as delamination and cracking. Triboluminescence is currently being looked at as a way of inundating composites with a sensory level mechanism for impact events. ZnS:Mn doped resin sensing plates are embedded within glass fiber-reinforced composites and are impacted at low velocities (3.45-3.51m/s). The damage created by the impact can be seen under black light analysis and allows for quick visual inspection of the composite. The striker during impact registers a bounce which can be used to determine final impact velocity, which in turn defines the force at impact. By measuring the amount of time between consecutive impacts, an indirect estimation of impact force was made using the temporal occurrence of triboluminescence. Triboluminescent emissions occurred for impacts greater than 300N. The measured impact energy averaged 36.79J (+/- 0.48). The calculated impact force and impact energy corresponded to the amount of damage area found on the composite, showing that triboluminescent crystal inclusion into composites can provide damage sensing capability to woven fiber composites.