Crashworthiness Enhancement of Kelvin-Cell Lattice Structures Through CFRP Rod Reinforcement: An Experimental and Data-Driven Assessment

Lattice structures are widely utilized in lightweight engineering due to their design flexibility and tailorable mechanical properties. However, polymer lattices often exhibit limited load-bearing capacity and moderate crashworthiness under compression. This study proposes a hybrid reinforcement strategy based on the integration of carbon fiber-reinforced polymer (CFRP) rods into polymeric Kelvin-cell lattices. The specimens were manufactured via masked stereolithography, and the effects of rod placement pattern, the number of rods, and rod-length configuration were systematically investigated under quasi-static compression. Crashworthiness was evaluated in terms of force–displacement response, deformation mode, and crashworthiness metrics. Compared with the empty Kelvin-cell lattice, the best-performing hybrid configuration increased energy absorption, specific energy absorption, and mean crushing force by approximately 356%, 307%, and 356%, respectively. Mechanistically, distributed rod placement promoted more uniform load sharing, while the effect of increasing rod number depended strongly on the rod-length configuration. In addition, delayed or sequential reinforcement strategies provided superior performance and an enhanced balance between energy absorption and force efficiency. Regression models and ANOVA consistently identified rod-length configuration as the dominant design variable. These findings demonstrate that CFRP rod reinforcement can effectively enhance the crashworthiness of polymeric Kelvin-cell lattices, provided that the rod placement pattern, rod number, and rod-length configuration are designed jointly.