Investigation of Tensile And Compressive Mechanical Behaviors in 3D Braided Composites Under Changing Thermal Environments

Introduction: The effects of varying thermal environments on the tensile and compressive mechanical behaviors of three-dimensional braided composites are investigated in this paper. Methods: A novel fusion of computational modeling and physical testing is employed to characterize the tensile/compressive behavior of 3D quadruple-orientation carbon/epoxy braided composites under changing thermal environments. This study uses the central trace lines of four helical fiber bundles to represent the spatial distribution of fiber bundles within the unit cell and the topological association of their main yarns. The load‒displacement curves and thermal stress field distributions of the 3D braided composites were obtained, and cross-validation between the numerical simulations and experimental data confirmed the fidelity of the computational model. Results: The longitudinal tensile strength of 3D quadruple-orientation carbon/epoxy braided composites is minimally sensitive to varying thermal environments, but significantly affects the longitudinal compressive mechanical properties. Moreover, temperature fluctuations intensified the weakening of the interface between the fiber bundles and the matrix, resulting in an uneven stress distribution within the material. This makes the material prone to local deformation and damage, thereby reducing its strength. Discussion: This study provides important model support and quantitative analysis methods for the accurate characterization of thermo-mechanical coupling behavior, revelation of damage mechanisms, and safety design and performance optimization of high-temperature engineering structures of woven composites, as well as references for related engineering patent research. Conclusion: This study provides reference data for research on the effects of 3D braided structures and the regulatory mechanism of the temperature gradient on the tension‒compression coordinated response of materials, and offers a theoretical basis for the design of aerospace thermal protection systems.