Nondestructive evaluation of composite materials using multi-axis fiber grating stain sensors

Fiber optic sensors may be used to monitor strain and temperature in composite materials. These measurements can be useful in determining rate and degree of cure of composite. Multi-dimensional strain measurements enabled by fiber gratings written onto polarization maintaining optical fiber enable monitoring changes in transverse strain, transverse strain gradients, and shear strain internal to composites and adhesive joints. This paper provides a brief historical overview of the usage of fiber sensors to provide strain measurements in composite parts, leading eventually to multi-axis strain sensing.