An experimental program was conducted to characterize the failure modes of fiber reinforced composite materials which are important to the automotive industry for both structural and non-structural applications. The composite materials utilized for this study included a randomly oriented, chopped glass reinforced polyester (SMC), Azdel's P-100 glass mat reinforced polypropylene, reaction injection molded (RIM) glass mat reinforced polycarbonate, Wellman's magnesium silicate filled nylon (Wellamid), and Dow's glass filled polyurea (Spectrum HT). The study included (1) conditioning and mechanical testing of samples, (2) fractographic examination, (3) development of a computerized atlas of all fractographs, and (4) design of a preliminary failure analysis expert system. Fractographs of all five materials unconditioned, and subjected to thermal aging or humidity aging identifying typical topographical features and fracture surfaces are presented for specimens subjected to tension, compression, flexure, impact, tension-compression fatigue, and flexure fatigue testing. The fractographic information obtained was summarized in two computerized atlases. In addition, the results were used to develop an expert system that guides the user in establishing potential failure modes based on the type of material, environmental conditions, and features observed on fracture surfaces. It should be noted that the expert system has been utilized for test specimens only and has not been tested on actual parts fabricated of the materials utilized in this study.