In sustainable design, material selection determines the performance of a product throughout its entire life cycle—from research and development, through manufacturing, use, to recovery and recycling. It is closely intertwined not only with environm...
In sustainable design, material selection determines the performance of a product throughout its entire life cycle—from research and development, through manufacturing, use, to recovery and recycling. It is closely intertwined not only with environmental, economic, and social impacts but also with technical factors that determine product performance and market acceptance. However, sustainability assessment becomes complex due to the heterogeneity of units and boundaries between indicators, the incompleteness of quantitative information, and the coexistence of conflicting relationships. Furthermore, differences in knowledge structures and value orientations among stakeholder groups—such as experts, designers, and users—make it difficult to reliably explain collective decision-making using only single-layer, single-method weight calculations.
To overcome these limitations, this study proposes an integrated priority derivation pathway reproducible through a hybrid multi-criteria decision-making (MCDM) procedure centered on refining the sustainable material evaluation indicator system while simultaneously securing multi-stakeholder judgments through cross-validation from a triangulation perspective. This is achieved using the Fuzzy Analytic Hierarchy Process (FAHP) and the Fuzzy Technique for Order Preference by Similarity to Ideal Solution (FTOPSIS) as core methodologies. FTOPSIS) as its core. First, an initial indicator pool was constructed through a PRISMA-based literature review. Subsequently, an expert Delphi process and indicator selection principles (J1–J6) were applied to eliminate issues of indicator redundancy, incomparability, and difficulty in quantification. The final evaluation indicator system comprises four Gate threshold indicators—such as compliance and safety—with a ‘non-complementary rule’ (One-Vote Veto) nature, and sixteen Score indicators that differentiate relative superiority after threshold fulfillment. The dual-track Gate–Score structure prevents core compliance requirements from weakening during weight conversion.
Methodologically, a three-step integration pathway was established comprising ‘consistency verification, reliability-based group-weighted integration, and FTOPSIS optimization’. In the first stage, the expert group derived importance information for the top-level dimensions using FAHP (Fuzzy Analytic Hierarchy Process), the designer group used an AHP survey, and the user group employed survey-based statistical verification (including reliability, validity, and regression analysis). Additionally, pairwise comparisons were performed for the four top-level dimensions and their corresponding sub-evaluation indicators derived from the expert and designer surveys. Consistency Ratio (CR) verification was used to confirm that the judgment matrices constructed by each group met the logical consistency level required for academic analysis. This process minimized subjective bias among evaluators and established a foundation for ensuring the reliability of the evaluation results. In the second stage, the individual weights of the three groups were integrated based on the Consistency Principle and the Dispersion Weighting Principle. Specifically, groups exhibiting concentrated evaluation opinions and low dispersion were considered to have higher judgment stability, leading to the assignment of higher group weights in those dimensions. This relatively strengthened the voice of those groups in the comprehensive decision-making process. This weight integration method objectively reflected each group's evaluation characteristics and played a key role in supporting rational decision-making that synthesizes diversified perspectives. Third, using FTOPSIS, a Positive Ideal Solution (PIS) and a Negative Ideal Solution (NIS) were established. Group evaluation values and the integrated fuzzy weights were input to calculate the Closeness Coefficient (CC) for each top-level dimension. The calculated closeness coefficients underwent a normalization procedure to enhance comparability, enabling the derivation of the overall priority ranking for the four top-level dimensions.
The empirical analysis involved 10 experts in materials, manufacturing, and management; 102 designers in industry, product, and material design; and 404 general users. The internal weighting structures for the top-level dimensions within each group were: Technology > Society > Economy > Environment for the expert group; Technology > Economy > Society > Environment for the designer group; and Society > Technology > Economy > Environment for the user group, confirming differences in priority structures among stakeholders. The FTOPSIS-based integration yielded a comprehensive priority order of Technology > Society > Economy > Environment, with normalized proximity coefficients calculated as approximately 0.458, 0.340, 0.202, and 0.000, respectively. Furthermore, sensitivity analysis regarding group reflection ratios and fuzzy scale changes showed no variation in the top-ranked priorities, confirming the stability of the results.
This study's theoretical contribution lies in presenting the ‘Dual-Wheel Priority’ interpretive framework. Specifically, in the practical context of material selection, the technological dimension is a necessary condition for product success, the societal dimension is a sufficient condition for market diffusion and recycling, and the economic dimension mediates constraints and expansion between the two. Conversely, insufficient policy and institutional internalization leads to the ‘Environmental Underweighting Paradox’ at the environmental level—a structural disconnect between macro goals and micro decision-making priorities. This phenomenon stems from factors such as the indirect and abstract nature of environmental impacts, their high correlation and substitutability with technical and economic indicators, and incentive gaps caused by externalities. Methodologically, this study presents a reproducible procedure: first, it stabilizes inputs by verifying the consistency and reliability of judgments; then, it integrates intergroup reliability-based weights; and finally, it derives the final priority order using FTOPSIS. Furthermore, the model can be adjusted based on policy and management variables, such as the reflection ratio between experts, designers, and users, and threshold settings, making it highly applicable in practice. This system not only enhances transparency in comprehensive decisions across diverse groups but also provides guidelines for achieving consistency assessment and collaboration among various stakeholders in future complex material selection environments. This study proposes adopting a two-stage material selection mechanism. In the first stage, critical conditions are set as thresholds that cannot be exceeded for safety, regulations, and key environmental criteria (E1/E2, T1/T3). The second stage evaluates and selects candidate materials using FAHP+FTOPSIS. Thus, this study establishes an FAHP-FTOPSIS-based group decision-making framework applicable in multi-objective, multi-criteria, and uncertain environments, validating its validity and applicability. Furthermore, by demonstrating the entire comprehensive evaluation process—comprising gate selection and FAHP-FTOPSIS integrated assessment—through case-based virtual simulation, it presented a procedural pathway for companies and designers to apply this methodology to actual material selection tasks. Empirical results indicate the overall priority order is Technology > Society > Economy > Environment. These results do not deny the value of the environment but suggest that the environmental dimension is undervalued under current institutional and market signal conditions. It indicates that environmental externalities must be transformed into constraints and benefits that decision-makers can recognize, quantify, and act upon through policy/institutional internalization, standard thresholding, and design management precedence. This study not only proposes a feasible, reusable weighted integration and alignment method for sustainable material selection but also provides an extensible governance methodology to explore how stable consensus can be formed under diverse stakeholders, complex objectives, and uncertain information.