Performance regulation and intelligent application of 4D-printed carbon fiber-reinforced TPU/PLA/CF composites
Abstract
This study aims to develop carbon fiber (CF)-reinforced thermoplastic polyurethane/polylactic acid (TPU/PLA) composite filaments tailored for 4D printing, with systematic investigation into the effects of CF content on material properties and shape memory behavior. Dog-bone tensile coupons, rectangular strips, complex honeycombs and biomimetic petals were additively manufactured by fused deposition modeling. Mechanical tests on dog-bone tensile coupons revealed that the incorporation of an optimal amount of CFs significantly enhanced the tensile strength of the composite. Uniaxial tensile tests with three parallel replicates were conducted, and all results were statistically processed as mean ± standard deviation. For instance, specifically, as the CF content increased from 0 wt.% to 2 wt.%, 4 wt.%, and 6 wt.%, the tensile strength rose from 3.5 ± 0.28 MPa to 5.5 ± 0.32 MPa, 8.08 ± 0.41 MPa, and 10.86 ± 0.53 MPa, respectively, representing a maximum increase of 210% compared to the pure TPU/PLA matrix. Thermal responsive shape memory tests demonstrate that CF fillers accelerate thermal-induced shape recovery, consistent with widely recognized heat conduction mechanisms reported in existing CF/polymer composite literatures. Specifically, the 6 wt.% CF sample attained roughly 80% recovery within 4 s and a final recovery ratio of 93.33 ± 1.08%. The honeycomb recovered 98.88% in 6 s under thermal stimulation, and the bilayer petals showed programmable sequential actuation, confirming their smart-structure potential. By simply replacing the petals with soft robotic grippers and using the same material system and printing process, diverse deformation sequences can be on-demand programmed. This strategy makes the low-cost, mass-producible fabrication of such intelligent structures readily achievable. These findings highlight the composite’s potential for flexible sensors and 4D-printed intelligent structures.