Crush energy absorption of composite channel section specimens

Carbon/epoxy square tubes and channel sections have been used in modern automotive and aircraft structures, respectively, as dedicated components designed to dissipate energy under controlled collapse. However, there are currently no specialized test methods for the characterization of Specific Energy Absorption (SEA) of composite materials. A systematic experimental investigation is conducted to evaluate the effect of geometric features on crush behavior. From a square tube, individual test segments are machined in order to isolate corner radii and flat sections of varying sizes, for a total of five different test geometries. Laminate thickness, material system, manufacturing process, and test methodology are kept constant throughout the study. For the material system and lay-up considered in this study, fiber tensile fracture and tearing at the corners is responsible for the vast percentage of the energy absorbed, while frond formation and splaying of the flat segments is responsible for a much lower percentage. An analytical expression is derived that accounts for the combined behavior of corner elements and flat segments in the crush behavior of more complex test articles, such as tubes.