An analytical technique is presented in this paper to analyze the crush strength (or force-deflection curve) of lightweight vehicle frame components which are made of: 1) high-strength steel, 2) aluminum alloy, and 3) fiber-reinforced composite. Experimental data are also included. It has been found that plastic flow of material and local buckling of sections are the key factors influencing the crush strength of metal structures, while elastic modulus and fracture strain are the dominant factors for fiber-reinforced composites such as glass-polyester and graphite-epoxy in their crush strength.
High-strength steel and aluminum alloy offer the best alternatives to mild steel in terms of meeting the required crush strength with maximum weight savings. For a given design peak force, use of fiber-reinforced composites can generally result in significant weight savings. However, when the energy absorption capability is concerned, fiber-reinforced composites such as glass-polyester and graphite-epoxy used in this particular frame application are not as efficient as their metal counterparts due to their brittle fractures at low strength values.