Analysis on microscopic damage evolution in components of resin-based composite materials for engine nozzles

To accurately characterize the influence of the mesostructure of three-dimensional needle-punched resin matrix composites on their mechanical properties, in-situ tensile micro X-ray computed tomography experiments were performed on the composites. By integrating image processing techniques and mesostructural reconstruction methods, quantitative analysis of fine structural features such as pores, cracks, and fiber architectures was completed, the evolution patterns of pore volume parameters were revealed and a three-dimensional strain field of the material was established. An image boundary path extraction algorithm and tomographic data reconstruction algorithm were proposed, enabling the construction of a layered finite element model. The results indicated that resin-based composites exhibited distinct damage evolution behaviors across different fiber architectures under tensile loading: damage in woven fiber layers primarily concentrated on the matrix and warp fibers; damage in unidirectional fiber layers occurred between fiber bundles and propagated perpendicular to the tensile direction; the maximum damage in non-woven fiber layers appeared at needle-punched structures, demonstrating that the needling process enhanced interlayer strength while inevitably degrading material performance. Under tensile loading, the woven fiber layer exhibited the highest load-bearing capacity, with damage state parameters remaining below 0.1 at a tensile strain of 3%. In contrast, the non-woven fiber layer, due to its higher porosity, showed the most severe damage under the same strain, with a damage state parameter of 0.605.