Strengthening adjustment of 3D printed continuous fiber reinforced composites with soft-hard mesoscopic structures

The integrated manufacturing of continuous fibers and resin matrix improves the mechanical properties of composite materials. Multi-material 3D printing technology provides a new technological means to realize the performance adjusting of composite materials. In the paper, a mesoscopic soft-hard dual-material strategy was proposed to strengthen the mechanical properties of composite structures. Tensile, impact, and interlayer shear properties of 3D printed continuous fiber reinforced composite were investigated experimentally. Results showed that the introduction of soft materials significantly affects these mechanical properties. Tensile modulus of sample has little change, being 42.44 GPa and 45.52 GPa before and after adjusting respectively. Tensile strength after adjuting was 1365.67 MPa, which was 46.25 % higher than that of PA-CCF composite. Impact strength increased from 30.26 kJ/m² to 39.47 kJ/m², which was 30.44 % higher than that before adjustment. Interlayer shear strength was 29.79 MPa and nonlinear deformation occurred, indicating that interlayer shear strength was sensitive to the introduction of soft materials. In addition, the distribution of soft-hard materials in the test specimen was characterized by microstructure. The failure mode of three types of samples was observed to explain the mechanism of mechanical properties change. The work can provide a reference for the performance adjusting of 3D printing soft-hard multi-material composite structures.