Experimental Evaluation of Compressive Properties for 3D-printed Continuous Carbon Fiber Reinforced Thermoplastics

Recent years have witnessed the development of 3D printing systems of continuous carbon fiber reinforced thermoplastics (CFRTP) for use in various applications. In terms of convenience, 3D printing of CFRTP has attracted considerable attention in various fields and industries. In this study, non- and open-hole compressive (NHC and OHC) properties of 3D-printed CFRTP were evaluated. In an NHC test, the compressive elastic modulus and strength in the fiber alignment (0º) direction were obtained with values of 58.1±4.0 GPa and 368.0±33.3 MPa, respectively. A theoretical study of the relationship between compressive strength and the initial fiber misalignment angle showed that the latter was greater than that of conventional hot-pressed CFRTPs, suggesting that the fiber waviness of 3D printing has a negative effect on the longitudinal compressive strength. In an OHC test, cross-ply laminates with center holes were prepared, where the OHC strength was 165.6±1.2 MPa. Both fracture surface and X-ray CT observations showed that kink bands occurred in the 0º layer at the edge of the center hole and that extensive delamination was observed at the 0º/90º interface around the hole. These observations suggest that the voids attributed to 3D printing merged with the delamination derived from fiber buckling near the center hole, leading to rapid expansion of the delamination.