Research on the Crashworthiness of Composite Foam Gradient-Reinforced Carbon Fiber Tubes

Due to the excellent energy-absorbing properties of the tubular structures, they are commonly used as energy-absorbing elements. In this paper, two types of hollow glass microspheres (HGMs) are mixed with epoxy resin to prepare composite foams. Three densities of composite foams were used as reinforcing materials for carbon fiber tubes (CFRTs). The CFRTs were reinforced with uniform and gradient structures (A, X, O). The axial compression tests were conducted under quasi-static loading to observe the mechanical properties, failure modes, and crashworthiness. The specific energy absorption (SEA) of the CFRTs reinforced with gradient structures to compare with metal energy-absorbing structures. The distribution and fragmentation of HGMs in the epoxy resin by were observed using a scanning electron microscope (SEM). The results show the C20/60 exhibits the highest peak force (PF) of 85.17 kN. Different types of composite foam and gradient designs have different effects on the structure’s failure modes, including tearing of the tube walls, shearing, and compression failure of the core. The SEM observed the HGMs of C20 are the most broken. The X-gradient composite foam-filled tube demonstrates superior crashworthiness compared to C20/60, except for the PF. The energy absorption (EA), SEA, meaning crushing force (MCF), and crushing force efficiency (CFE) have improved by 9.8%, 17.1%, 9.8%, and 25.9%, respectively. The SEA of X is higher than the aluminum round tube, the aluminum alloy secondary nested square tube, and the magnesium round tube, the value is 3.6, 2.7, and 1.3 times, respectively. Therefore, the composite foam-reinforced CFRTs are an ideal energy-absorbing configuration.