Applications of diffuse reflectance fourier transform infrared spectroscopy to fiber‐reinforced composites

Abstract Diffuse reflectance Fourier transform infrared (FT‐IR) spectroscopy can be used to obtain infrared spectra directly from the surface of composite materials with little or no sample preparation. It is thus of interest as a nondestructive method for industrial inspection. In many cases, the IR spectra provide detailed information concerning the chemical composition and molecular structure of the material. The technique works particularly well for carbon‐fiber composites. This paper describes the principles involved, some factors which influence the quality of the spectra, and a number of examples of applications. These include the characterization of epoxy matrices (composition, curing, degradation), the detection of surface contamination, and the determination of the degree of crystallinity in poly(phenylene sulfide)‐based composites.