Evaluation of double- and triple-coupled triggering mechanisms to improve crashworthiness of composite tubes

A reasonable coupled triggering mechanism has greater potential to produce a progressive crushing mode and improve the crashworthiness of composite absorbers. To clearly understand coupled triggering mechanisms, the crashworthiness of composite tubes triggered by double- and triple-coupled triggers is comprehensively evaluated. Five double-coupled triggers including chamfer/hole, chamfer/slit, chamfer/saw tooth, chamfer/plug, and chamfer/material degradation (C-GMD) triggers are designed. To exhibit better crashworthiness, triple-coupled triggers are designed by coupling each double-coupled trigger with a plug trigger. Based on Finite Element Methods (FEM), comparisons of the crashworthiness of tubes using double- and triple-coupled triggers are conducted. Effects of width and height of plug on failure modes are further studied. From the predicted results, coupled triggering and energy-absorbing mechanisms are extensively revealed. Double-coupled triggers further weaken triggered regions to reduce the initial peak while triple-coupled triggered tubes improve Energy-Absorption (EA). Triple-coupled C-GMD-plug trigger presents 26.62% higher EA than C-GMD trigger. Material folding and buckling mechanisms have great effects on the material accumulating process. Failure modes are highly sensitive to plug width, plug height and a combination of both. Some design proposals for C-GMD-plug trigger are recommended.