Evaluation of Shear Modulus of Lotus Root and Beetle Wing Inspired Particulate Hemp-PLA Cores Using ASTM E756

This study investigates the mechanical characterization of bio-inspired cellular cores utilizing polylactic acid (PLA) reinforced with hemp powder. Two distinct core geometries lotus root inspired and beetle wing inspired—were fabricated using fused deposition modeling with varying hemp content (0%, 2.5% and 5% by weight). Sandwich beam specimens with galvanized iron facings were evaluated using ASTM E756 standards for damping properties. Results demonstrated that lotus root-inspired cores achieved superior shear modulus values of 4.32 MPa for pure PLA representing a 20.7% advantage over beetle wing designs (3.58 MPa). Lotus root cores provided enhanced damping characteristics with loss factors up to 0.1497, while beetle wing cores showed optimal damping at 2.5% hemp content (0.1165 loss factor). Hemp reinforcement at 2.5% weight content emerged as the optimal composition for balanced performance, reducing core density by 31.9% while maintaining mechanical integrity. The 5% hemp composition achieved maximum weight reduction (37.2% density decrease) with superior damping characteristics but significant stiffness reduction. The bio-inspired geometries demonstrated 15-20% superior specific strength compared to conventional honeycomb designs, validating the feasibility of sustainable composite production through additive manufacturing with natural fiber reinforcement.