Sustainability-oriented multimaterial topology optimization: designing efficient structures incorporating environmental effects

We propose a multimaterial topology optimization framework for sustainable infrastructure design with substantial mechanical and economical advantages. The framework optimally harnesses the mechanical superiority of steel and the environmentally sustainable properties of biomaterials, such as laminated bamboo and timber, to design stiff, strong, and sustainable structures. The fibrous characteristics of biomaterials are incorporated using the transversely isotropic constitutive relation and Tsai–Wu failure criterion, while steel is assumed isotropic with von Mises yield criterion. Two sustainability-oriented formulations are proposed to accommodate different design scenarios, accounting for performance, environmental impacts, and economic costs. Both formulations are capable of designing optimized steel-biomaterial hybrid structures with significant sustainability improvements. Through 2D and 3D example problems, we demonstrate that the proposed framework effectively leverages the unique advantages of steel and different biomaterials to strive an ideal balance among diverse mechanical, economic, and environmental design requirements. The results indicate that both steel and biomaterials are essential to achieve cost-effective sustainable design solutions with enhanced mechanical performance. Specifically, biomaterials are predominantly used in low or moderately stressed members, while steel is optimally utilized in high-stressed or primary load-bearing members. The proposed framework presents a rational design paradigm for high-performance and sustainable multimaterial engineering structures that can benefit construction industries from both economic and environmental perspectives.