Depth-resolved stress field measurement of multilayered system using swept-source polarization-sensitive optical coherence tomography

Non-destructive, layer-resolved stress field measurements of multilayered systems are essential for structural optimization, mechanical property induction and product inspection. This paper presents a depth-resolved stress field measurement method for multilayered systems based on swept-source polarization-sensitive optical coherence tomography (SS-PS-OCT). A circularly polarization state (CPS) SS-PS-OCT stress measurement setup was developed, enabling real-time visual and digital adjustment of the polarization state. The SS-PS-OCT stress birefringence response of the multilayer sample is determined, and a depth-resolved stress mapping algorithm is proposed, both based on the re-modeled sample with equal thickness slices. Tensile experiments on rubber samples show good agreement between tensile machine and PS-OCT measurements. The stress field of a bilayer thermoplastic elastomer (TPE) specimen shows the high accuracy of our proposed method in determining depth-resolved stress fields. All the experiments show that the method has an error in stress magnitude of less than 5% and an error in principal stress direction of less than 6%, the accuracy has been greatly improved. The SS-PS-OCT-based depth-resolved stress field measurement method expands the internal stress measurement and has great potential for the internal mechanical measurement of multilayered systems.