A mesoscale structure design methodology based on strain energy to enhance mechanical properties in additive manufacturing

Purpose In this study, a novel methodology for the design of mesoscale structures is proposed. This methodology is based on the U* theory, where U* is calculated by strain energy. The purpose of this study is to enhance the mechanical performance of material extrusion (MEX) structures by overcoming the limitations of conventional grid infill patterns. Design/methodology/approach A strain energy-based framework is developed to optimize the printing path by constructing U* value distributions through numerical simulations and experimental validation. Load transmission paths are delineated via contour lines, regional partitioning is conducted using second-order difference analysis, and optimal path orientations are iteratively determined. A variable-angle lattice structure aligned with load path trajectories is subsequently generated. Findings Compared to conventional grid structures, the mesoscale structure based on U* theory achieves a 33.9% increase in ultimate load-carrying capacity and a 10.4% improvement in stiffness. When compared to principal stress trajectories structures, it demonstrates a 6.9% enhancement in ultimate load-carrying capacity. Experimental and simulation results are consistent, validating the effectiveness of this approach. Originality/value This research pioneers the integration of U* theory into MEX mesoscale structure design, realizing cross-scale optimization from macro-scale load analysis to mesoscale path planning. It establishes a theoretical and methodological foundation for the development of high-performance, customized additive manufacturing structures.