Through-thickness strain field measurement of polymethyl methacrylate sheet using phase-contrast optical coherence tomography

Strain field characterization for evaluating the mechanical properties of polymethyl methacrylate (PMMA) is highly significant. This study establishes a method based on phase-contrast optical coherence tomography for the through-thickness strain field measurement of PMMA sheets, which utilizes two methods of probing light passing through the specimen thickness in parallel or oblique to estimate thickness shrinkage and elongation. Two PMMA sheet specimens were measured under stretching for the validation test—one with and the other without a slotted hole. The results show that all the measured strain fields are non-uniform, stress concentration occurs in the defect, and Poisson's ratio of PMMA in this paper is 0.35–0.37. These results indicate good rationality, proving the feasibility of the proposed method for strain measurements. •The through-thickness strain field of the PMMA sheet was successfully measured using phase-contrast optical coherence tomography (PC-SOCT).•We utilized two methods of probing light passing through the specimen thickness in parallel or oblique to estimate thickness shrinkage and elongation.•The PC-SOCT method features quantitative and dynamic sensing advantages for studying the mechanical properties of polymers.