Structure–property relationships in 3D-printed onyx-based composites reinforced with continuous fibers: role of temperature and fiber orientation

This study investigates the flexural performance of 3D-printed continuous fiber-reinforced composites, focusing on the influence of fiber types, orientation, and temperature. Using a carbon, glass, kevlar fiber- and Onyx matrix- filaments, specimens were fabricated as 24 or 30-layer composites. Three-point bending tests were conducted under different temperatures. The results reveal a significant influence of fiber type and orientation. Carbon fiber composite showed the highest strength of 281 MPa at 0° orientation and 127 MPa at 90° orientation at RT. At -20 °C, Carbon, Glass and Kevlar composites revealed flexural strength of 422, 308 and 188 MPa respectively (0°). Similarly, with an increase in temperature, a decrement in flexural properties can be observed in all the fiber types. The modulus for kevlar decreased from 8.29 to 5.71 to 4.15 GPa with an increase in temperature from -20 to 27 to 85 °C. Additionally, microscopic analysis highlights the failure mechanisms, including fiber pull-out, delamination, and matrix softening. Grey relation analysis used two mutually conflicted parameters (strength, cost) and reported the best and worst composite amongst 18 combinations considered. The findings provide valuable insights for optimizing the design of 3D-printed composites at different fiber orientations and temperatures enhancing their applicability in structural applications.