Flexural behaviors and failure mechanisms of CFRP sandwich structures with enhanced dual-phase lattice cores

Inspired by bionic/metallurgical microstructures, novel dual-phase lattice/ Carbon Fiber Reinforced Polymer (CFRP) composite sandwich structures are proposed to improve the energy absorption (EA). The composite sandwich structures for different dual-phase strengthening strategies are designed, where the topology optimization is used to yield efficient lattice distribution configurations. The experimental samples are fabricated by 3D-printing and three-point bending tests are conducted. The flexural failure process and failure modes are observed and analyzed to reveal the failure mechanisms. Results show that DPL-1-CFRP and DPL-2-CFRP have higher peak load (+24.8 % and 18.0 %), post-peak average load (42.6 % and 20.8 %) and specific energy absorption (+7.8 % and + 21.1 %) compared to SPL-1-CFRP. It is indicated that the interactive failure mechanism of dual-phase lattice is effective in improving the mechanical properties of sandwich structure. It represents the occurrence of synergistic deformation between struts rather than a single brittle fracture. Finally, several potential failure mechanisms for the separation of the core and end faces are revealed. This novel concept and structural design greatly contribute to improve mechanical properties of sandwich structure.