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An analogy between damage inflicted by a single-point hard-particle impact and damage inflicted by inserting a flaw of known dimensions in a static tensile coupon is discussed. The results suggest that residual strength can be predicted as a function of kinetic energy of impact by executing two experiments, a static tension test on an unflawed specimen and a static tension test on a coupon previously subjected to a single-point impact. The model appears to be accurate for impact velocities which are less than the penetration velocity. For velocities above complete penetration, the residual strength is identical to the static strength of a coupon with a hole having the same diameter as the impacting particle. Comparison of various materials indicates that the impact strength of composite materials is strongly influenced by the strain energy to failure of the reinforcement.

Recent developments in hot-melt impregnation, extrusion, and thermoforming offer multiple avenues for the design and manufacture of low-cost thermoplastic composites for mass transit and automotive applications. Fiber reinforced thermoplastics such as glass/polypropylene (glass/PP) have found their applications in front-end bumper beams, under body shields, and other automotive applications. These materials also have potential usage in mass transit vehicles, such as buses. The present study focuses on the design and manufacture of a segment of the floor of a mass transit bus using glass/PP woven tape forms developed through a hot-melt impregnation process. An initial study on the existing mass transit buses found that a metal skeletal frame and plywood panels are used in the construction of the floor structure. The representative thermoplastic composite floor segment featured a glass/PP woven tape material, belt-pressed to form a flat laminate, and adhesively bonded to a vacuum thermoformed ribbed laminate. A combination of analysis software including Pro/Engineer, Hyper Mesh, and ANSYS 7.0 were used for the design and analysis. Weight savings up to 40% were realized using glass/PP woven tape thermoplastic composites as compared to the conventional metal/ plywood design