3d printable joint bracket

3D printable mechanical load-bearing joint, strictly within 50mm×50mm×40mm envelope. Main structure: 8mm tall rectangular base + 32mm tall isosceles trapezoid, trapezoid top width 22.71mm, bottom width 50mm, total height 42mm, fully symmetric design. Material: PLA plastic, density 0.8g/cm³, total mass <30g, target 23-27g, maximize load-to-mass ratio. Load requirement: vertical static load capacity ≥80kg, compressive and shear resistant, all corners with R1mm fillet to avoid stress concentration, suitable for PLA brittleness. Hole requirements: - Φ10mm through hole at center of trapezoid upper part, hole center 10mm from top, 3mm thick solid reinforcement ring around the hole; - 4×Φ5.5mm through holes on 50×50mm mounting end face, hole coordinates (origin at bottom-left corner): (10,10), (40,10), (10,40), (40,40), compatible with M5 bolts. Structure optimization: 2mm external wall thickness, internal high-strength triangular truss/lattice bionic topology structure, retain main load path