Nonintrusive Through Thickness Stress/Strain Sensor for Composites

The Air Force has indicated that current and future research in the area of high velocity ballistic impact will require the development of unique nonintrusive stress/strain measurement techniques for composite materials. Foster-Miller proposes a unique and highly effective solution to the problem of through thickness stress wave measurement in composite structures which uses through thickness embedded fiber optic sensors. The technique builds upon past research at Foster-Miller where fiber optic Bragg grating sensors were embedded through-thickness in composite laminates for detection of internal delaminations and crack propagation. This Phase I proposes to develop the technology required to resolve the strain distribution as a function of length along the sensor so that non uniform strain distributions and stress wave propagation during ballistic impact can be measured. Additionally, the proposed technology will enable the measurement of through thickness strains in composite structures for static and dynamic structural applications. There is no currently available technology which provides these capabilities.