Enhanced energy absorption and reusability of 3D printed continuous carbon fibre reinforced honeycomb beams under three-point bending loads

The integration of continuous carbon fibre (CCF) into 3D printing technology enables the fabrication of enhanced honeycomb structures. While CCF reinforcement demonstrates considerable potential for improving structural performance, comprehensive research is required to evaluate these fabricated honeycomb structures under bending loads, particularly regarding their shape-memory characteristics and reusability under cyclic loading conditions. This study investigates the response and energy absorption performance of novel reusable 3D-printed honeycomb beams reinforced with CCF under three-point bending loads through both experimental and numerical approaches. Specimens were manufactured using a dual-nozzle fused deposition modelling 3D printer by combining a thermoplastic polyurethane (TPU) matrix with varying CCF volume fractions. The mechanical behaviour was characterized through force-displacement curves obtained from monotonic and cyclic three-point bending experiments. Finite element models were developed and experimentally validated to simulate the mechanical responses, enabling parametric studies of CCF volume fraction and impact velocity effects. The cyclic bending experiments demonstrated reusability, with specimens maintaining at least 61 % of their initial energy absorption capacity after 10 cycles. Impact velocity proved to be a significant factor in honeycomb beam behaviour, with higher velocities leading to increased deformation and energy absorption. However, the incorporation of CCF introduced repulsive forces that caused fluctuations in force-displacement curves at higher speeds. Higher CCF volume fractions enhanced both load-bearing capacity and energy absorption, with the highest CCF content model achieving a 7.24 % weight reduction while improving energy absorption by 59.45 %. These findings provide valuable insights for designing reusable lightweight honeycomb beams with superior energy absorption capabilities.