Effects of loading rate and temperature on crushing behaviors of 3D printed multi-cell composite tubes

Fiber-reinforced composites are widely used in energy absorbers structures due to their high specific strength and specific modulus. However, composite materials are sensitive to loading rate and temperature conditions. In this paper, multi-cell hexagonal tubes (MHT) were prepared using fused deposition modeling by carbon-fiber -reinforced polyamide. To study the loading rate and temperature effects on crushing behaviors, compression at constant rates of 10 mm/min, 100 mm/min, 500 mm/min and impact test with an initial velocity of 10 m/s at four different temperatures (-40 degrees C, -10 degrees C, 20 degrees C and 50 degrees C) were investigated. The results showed that MHTs exhibited progressive folding mode under compression conditions and the specific energy absorption increased with the increasing compressive rate. The collapse mode presented a ductile-to-brittle transition when loading condition changed from compression to impact. The peak crushing force of MHT increased with increasing loading rate. The deformation modes of MHT were influenced significantly by the temperature. Compared to the compression at 20 degrees C, it was increased that the half-wavelength of MHT at 50 degrees C, while the MHT presented continuous brittle fracture at -10 degrees C and -40 degrees C. In addition, the crashworthiness of MHT were less affected by temperature under impact than that of compression. Dynamic loading condition inhibited the material softening at high temperature. Therefore, at high temperature, MHT under impact condition show higher peak crushing force and specific energy absorption than those under compression condition.