From cracks to informed circularity: Mechanics-guided decisions via high-throughput in situ failure analysis of recycled plastics.

Materials under real-world conditions are subjected to coupled mechanical and chemical stressors, yet current testing platforms cannot capture their combined effects on material behavior and failure, particularly when multiple specimens are required for robust measurements. This limitation is acute for recycled materials, whose performance cannot be inferred from a few conventional tests. Here, we introduce an in situ, high-throughput photoelasticity platform for multispecimen testing under controlled chemical conditions with full-field stress visualization. Using recycled polyethylene terephthalate (rPET) as a model system under simultaneous loading and varying pH, we reveal earlier onset of crack propagation and shorter lifetimes compared to virgin PET and quantify mechanochemical process zone expansion from ∼0.08 to ∼0.25 millimeters before failure. Extending these findings to landfill geotextiles, a growing application of rPET, we show that alkaline degradation erodes rPET environmental and economic advantages over virgin PET above pH 9. This integrated workflow, linking instrumentation to mechanistic insights to sustainability-informed decision-making, can accelerate the deployment of emerging, circular materials.