Enhancing carbon fiber thermoplastic sandwich structures with springback effect

In this research, a sandwich structure is manufactured using a thermally deformed (springback) core. Non-woven carbon fiber reinforced thermoplastic (NW-CFRTP) was used for the core, and uni-directional carbon fiber reinforced thermoplastics (UD CFRTP) and carbon fiber reinforced thermoplastics sheet molding compound (CFRTP-SMC) were used for the skin. Statistical flexural properties were investigated by conducting three-point bending experiments. Specimens with different springback ratios were assessed, and the critical springback ratios of the individual core and whole sandwich structure indicated the peak points of mechanical properties in the corresponding tests. Diverse results were acquired and a springback ratio of approximately 1.7 was found to give optimal static mechanical properties during various scenarios. Different fracture models that appeared during the research were also studied, and improvements were made based on the findings. To improve the properties along the thickness direction, the molding method and material set were improved, and the enhancement of interlaminar properties also contributed to better mechanical properties. Specifically, the energy absorption capacity of the structure more than doubled. Stable and ductile sandwich structures were achieved with a density lower than water, and the excellent specific mechanical properties could open up new avenues for the application of recycled carbon fibers.