Effects of Epoxy Molecular Structure on Photoelastic Properties for Micro‐Stress Optical Measurement

ABSTRACT Optical measurements can overcome bandwidth limits in space charge detection, achieving high resolution, and rapid measurement. As a key component, the photoelastic properties of sensor core materials determine system accuracy. Therefore, analyzing and designing the core sensor material with high photoelastic sensitivity can contribute to further improving the testing capability of the platform. Epoxy resins are ideal for photoelastic sensors due to their diverse types and pronounced stress‐birefringence effects, yet systematic studies on their photoelastic performance remain lacking, which impedes rational material design. This study elucidates molecular structure effects on epoxy resins' photoelastic performance by comparing five types with distinct chain configurations under uniaxial stress and elastic wave conditions. Molecular dynamics simulations reveal that microscopic chain motions govern stress‐induced refractive index changes, while structural analyses identify resin suitability for different testing scenarios. Results show E‐51 and F‐51, with their ether‐rich, benzene‐ring structures, and long flexible chains, exhibit superior photoelastic performance under uniaxial stress, while DE184, GTE, and TTA21, featuring compact chains with high rotational mobility, are more suitable for high‐frequency elastic wave measurements. Based on the analysis results, modification strategies such as adjusting molecular chain size or introducing high molar refractivity groups in appropriate proportions are proposed, which are expected to further improve the photoelastic performance of the materials. This work establishes a theoretical foundation for designing high‐performance photoelastic sensors used in space charge optical measurement.