Performance enhancement, negative stiffness structural characterization, and energy absorption mechanisms of 3D-printed continuous carbon fiber reinforced composites

Negative stiffness (NS) structures leverage multi-stable mechanisms to demonstrate energy-absorbing capabilities. Nonetheless, existing implementations are impeded by material and manufacturing, which constrain load-bearing capacity, reusability, and energy absorption efficiency. The observed flexural bounce behavior in beam structures offers a promising avenue for achieving multi-stability and reusability. Consequently, we utilize continuous carbon fiber reinforced thermoplastic polymers (CCFRTP) and three-dimensional (3D) printing to fabricate NS structures featuring cosine beam cells, aiming to elucidate the mechanisms through which CCFRTP modulates their multi-stability. Prior to this, a wet twisted method for continuous carbon fiber (CCF) was employed to augment the mechanical properties and elucidate the failure behaviors and interfacial adhesion mechanisms. Building upon this, a one-stroke path planning model was utilized to delve into the bistability principles and energy absorption mechanisms of the CCFRTP cosine beam structure. The displacement-controlled loading and unloading experiments were conducted to assess the energy absorption characteristics of the structure in both energy-locked and repetitive energy absorption modes. Furthermore, a dual-unit assembly structure was fabricated to investigate its overall deformation and energy absorption properties, thereby validating the feasibility of the negative stiffness honeycomb structure. This approach holds promise for aerospace and naval applications requiring efficient energy absorption under large deformation and high loading.