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<div class="section abstract"><div class="htmlview paragraph">Evolving fuel efficiency and emissions standards, along with consumer demand for performance, are strong pressures for light-weighting of performance oriented motorcycles. The field of topology optimization (TO), with the extension of multi-material topology optimization (MMTO) provide manufacturers with advanced structural light-weighting methodology. TO methodology has been adopted in many industries, including automotive where light-weighting assists in meeting efficiency regulations. The development of process specific manufacturing constraints within MMTO is a critical step in increasing adoption within industries dealing with manufacturing cost restrictions. This capability can decrease design complexity, lowering manufacturing costs of optimization solutions.</div><div class="htmlview paragraph">A conventional all-aluminum perimeter style motorcycle chassis is analyzed to develop baseline compliance (total strain energy) metrics. An MMTO design space is created and optimized with steel and aluminum, such that results match the baseline design weight. This formulation demonstrates increased structural efficiency through stiffer structures at equivalent weight. Results are generated with standard MMTO, symmetry, and extrusion constraints to demonstrate utility of these manufacturing constraints. Material ratios are used to enforce lower cost material distribution selections.</div><div class="htmlview paragraph">The usage of MMTO with manufacturing and material ratio constraints has resulted in up to 60.4% reduction in structural compliance of designs, and a multitude of lower cost alternative designs. The usage of symmetry constraints provides effectively identical results to standard MMTO, with a computational time reduction of 29%. Extrusion constraints demonstrate decreased manufacturing difficulty with a computational time reduction of 52% and structural performance penalty of 58.6% from the lowest compliance MMTO result. The enforcement of steel has demonstrated a decrease in structural performance (increase in compliance) and material costs, with varying degrees depending on manufacturing constraints and enforcement limits. The MMTO based designs provide a range of solutions to designers, which can be selected based on the importance of structural efficiency, manufacturing difficulty, and material costs.</div></div>

<div class="section abstract"><div class="htmlview paragraph">The field of topology optimization (TO) has been evolving rapidly, notably due to the emergence of multi-material topology optimization (MMTO) algorithms. These developments follow the establishment of TO tools within industry, which has been accelerated and promoted through the introduction of various manufacturing constraints within algorithms. The integration of manufacturing constraints within MMTO is critical for promoting industry usage and adoption of these new software algorithms, as current usage of MMTO is dissuaded by the typically complex design solutions.</div><div class="htmlview paragraph">The presented MMTO implementation is an extension of classical single-material topology optimization (SMTO). The TO problem is expanded to consider both material existence and selection, solid isotropic material with penalization (SIMP) is utilized for material interpolation. The method of moving asymptotes (MMA) has been integrated into MMTO as the optimization algorithm as it can handle large-scale problems with many design variables.</div><div class="htmlview paragraph">A design variable mapping system has been incorporated into MMTO, which determines element groups based on symmetry or extrusion manufacturing constraints. The design variables of the group elements are constrained to equivalent values, resulting in either extruded or symmetric MMTO geometry. Several problems, of varying scale and optimization problem statement are solved using MMTO without manufacturing constraints, MMTO with extrusion, and MMTO with symmetry constraints. The optimized geometry and numeric performance are analyzed to determine the feasibility of the manufacturing constraints in reducing computational time and increasing design manufacturability. These benefits are contrasted against the reduction in structural performance; a consequence of reduced design freedom when enforcing manufacturing constraints.</div></div>

<div class="section abstract"><div class="htmlview paragraph">Topology optimization (TO) represents an invaluable instrument for the structural design of components, with extensive use in numerous industries including automotive and aerospace. TO allows designers to generate lightweight, non-intuitive solutions that often improve overall system performance. Utilization of multiple materials within TO expands its range of applications, granting additional freedom and structural performance to designers. Often, use of multiple materials in TO results in material placement that may not have been previously identified as optimal, providing designers with the ability to produce novel high performance systems. As numerous modern engineering materials possess anisotropic properties, a logical extension of multi-material TO is to include provisions for anisotropic materials. Herein lies the focus of this work.</div><div class="htmlview paragraph">A TO algorithm capable of considering anisotropic material properties is used to investigate a case study on the design of an automotive hood panel. A baseline aluminum hood panel is used to generate stiffness targets for optimization, followed by the generation of a design space model to allow the algorithm to determine optimal material placement. Optimization is undertaken with two types of AS4 continuous carbon fiber reinforced epoxy, each in two orientations. Optimal hood panel solutions that maintain stiffness levels of the conventional baseline are achieved. The mass of the design space is minimized, and constrained through the baseline displacement values. The effect of hood panel thickness and offset distance between panel layers is also investigated.</div><div class="htmlview paragraph">The optimal topologies indicated an overall mass savings of up to 44.5% in relation to the baseline, while maintaining hood panel stiffness. Comparative mass savings decreased as hood panel thickness increased and offset distance decreased. The allocation of stiffer materials was observed near locations of applied loads and constraints, with highly anisotropic materials placed along hood panel extremities. The practicality of anisotropic multi-material TO in lightweight design was thus demonstrated.</div></div>

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