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<p>This paper reports the effects of cryogenic cycling range on dynamic mechanical responses, directional compressive stiffness and surface strain localization of 3D braided composites. Specimens were subjected to five cooling-heating cycles from room temperature to 20, 60, 100, 140, and −180 ℃, followed by dynamic mechanical analysis (DMA), in-plane/out-of-plane compression, and digital image correlation (DIC) measurements. The results show that the storage modulus (E’) is the most sensitive parameter to cryogenic cycling. E’ remained stable or slightly increased after mild cycling, with a 9.24% increase in the −20℃ group. When the lowest cycling temperature decreased below −100°C, E’ began to decline, reaching a maximum reduction of 36.19% at 180&#xa0;°C. Compression tests revealed stronger degradation in the in-plane direction, where compressive modulus decreased by up to 34.87%, compared with only 5.93% in the out-of-plane direction. DIC results showed that surface strain fields evolved from uniform deformation to localized strain concentration. Localization appeared earlier and varied more strongly during in-plane compression, whereas out-of-plane deformation remained more stable. These results indicate that the residual responses after cryogenic cycling are governed by coupled changes in matrix/interface stiffness, anisotropic load transfer, and surface strain localization.</p>

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Residual Dynamic Mechanical Responses and Compressive Strain Localization of 3D Braided Composites After Cryogenic Cycling

  • 期刊论文

  • 发表日期：

    2026年7月24日

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  • Qiannan Li,
  • Huijuan Li,
  • Baozhong Sun,
  • Meiqi Hu,
  • Bohong Gu

摘要

This paper reports the effects of cryogenic cycling range on dynamic mechanical responses, directional compressive stiffness and surface strain localization of 3D braided composites. Specimens were subjected to five cooling-heating cycles from room temperature to 20, 60, 100, 140, and −180 ℃, followed by dynamic mechanical analysis (DMA), in-plane/out-of-plane compression, and digital image correlation (DIC) measurements. The results show that the storage modulus (E’) is the most sensitive parameter to cryogenic cycling. E’ remained stable or slightly increased after mild cycling, with a 9.24% increase in the −20℃ group. When the lowest cycling temperature decreased below −100°C, E’ began to decline, reaching a maximum reduction of 36.19% at 180 °C. Compression tests revealed stronger degradation in the in-plane direction, where compressive modulus decreased by up to 34.87%, compared with only 5.93% in the out-of-plane direction. DIC results showed that surface strain fields evolved from uniform deformation to localized strain concentration. Localization appeared earlier and varied more strongly during in-plane compression, whereas out-of-plane deformation remained more stable. These results indicate that the residual responses after cryogenic cycling are governed by coupled changes in matrix/interface stiffness, anisotropic load transfer, and surface strain localization.