Fiber-reinforced polymer matrix composites (PMCs) are among the most common materials in use in modern aircraft. In fact, the new Boeing 787 is 50% composite by weight compared with just 12% composite by weight in the Boeing 777. However, the resin matrices are susceptible to heat damage, and in particular suffer from loss of interlaminar shear strength. The Laser-Induced Fluorescence (LIF) Composite Heat Damage Detector was developed by Oak Ridge National Laboratory, Oak Ridge, Tenn., and Galt Technology LLC, Knoxville, Tenn., with rapid and non-destructive heat damage assessment of PMCs in mind. The LIF unit contains an excitation laser, a spectrometer, a linear-array photomultiplier tube detector, and an analog-to-digital convertor. The detector collects fluorescence spectral information from suspected damaged areas, which is then correlated with thermal history data from PMC samples. Controlled via laptop, the LIF has a marked advantage over previous methods, which were limited to ultrasonic inspection and visual observations.