Natural-Based Composites: A Framework for Interpreting Engineering Evidence

Natural-based composites have received increasing attention as engineering materials because they can incorporate renewable feedstocks, valorize agro-industrial residues, and support more circular resource use. Their engineering interpretation, however, remains challenging because reported performance depends on formulation, reinforcement or filler characteristics, interphase condition, processing history, defect state, environmental exposure, and testing context. This review organizes a bounded evidence set, selected using explicit evidence-relevance criteria, into evidence maps to examine how these variables affect cross-study interpretation and evidence reuse. Across the mapped studies, nominal material designation alone did not provide a reliable basis for comparison, and recurring gaps were identified in defect characterization, durability and retained-property assessment, and validation of end-of-life claims. Quantitative comparisons were retained only when the relevant formulation, processing, exposure, and test conditions were sufficiently defined. Based on these observations, the review proposes a qualification-oriented framework comprising an Evidence Readiness Score, four Evidence Readiness Levels, and a staged roadmap linking evidence completeness with comparison, scale-up, predictive design, and application-specific qualification. The resulting framework provides a structured basis for determining whether reported evidence is sufficiently complete and contextually defined to support comparison, scale-up, and application-specific engineering decisions.