Laser Raman Spectroscopy; A New Stress/Strain Measurement Technique for the Remote and On-Line Nondestructive Inspection of Fiber Reinforced Polymer Composites

A new nondestructive evaluation technique for stress/strain measurements in fiber-reinforced polymeric composites, laser Raman spectroscopy (LRS), has been developed over the past few years. When coupled with an optical microscope it is highly selective and can probe areas as small as 1–2 μm. In this review, the principles of LRS are explained. It is shown that LRS is an ideal technique for conducting stress or strain measurements in fibers, for assessing the strength of the fiber-matrix bond in composites, and for mapping fiber stresses and strains in commercial composite panels. It is envisaged that within a few years, major composites manufacturers and users will routinely employ remote LRS for in-house (or even in-service) inspection of composite components.