2.5D机织石英纤维增强树脂复合材料不同方向力学性能测试与模量预测2.5D机织石英纤维增强树脂复合材料不同方向力学性能测试与模量预测

石英纤维增强树脂复合材料常用于多物理场耦合环境下，为保证足够的层间性能，常采用2.5D机织的结构形式。本文对一种浅交弯联2.5D机织石英纤维增强双马树脂复合材料的三维力学性能进行全面测试，对比分析了材料在不同方向的拉伸性能和压缩性能，以及面内、面外剪切性能。测试结果表明，该复合材料的纬向拉伸、压缩模量略高于经向，而拉伸、压缩强度远高于经向，导致经向和纬向拉、压破坏模式差异显著，拉伸时弯曲的经向纤维被拉断，平直的纬向纤维劈裂，压缩时平直的纬向纤维压断，弯曲的经向纤维屈曲。同时，该种材料具有较高的面内、面外剪切变形能力。此外，本文基于混合定律，提出了一个2.5D机织复合材料经、纬向模量估算公式。基于材料微观结构特征，以包含经纱和纬纱的一个单胞作为代表性体积单元，建立有限元模型，预测该2.5D机织复合材料经向模量，预测结果与试验结果吻合很好。本文的研究对2.5D机织石英纤维/双马树脂复合材料的研发具有一定的指导意义。 

Mechanical properties testing for 2.5D quartz fiber reinforced resin composites in different directions and module prediction

Quartz fiber reinforced composites are often used in multi-field coupling environments. To ensure enough interlaminar performances, quartz fiber reinforced composites often exist in the form of 2.5D braided structures. In this paper, the three dimensional mechanical properties of a 2.5D quartz fiber reinforced bismaleimide resin composites (shallow bend-joint) were comprehensively tested. The tensile and compressive properties in different directions, and in-plane and out-of-plane shear property were compared and analyzed. It has been found that the tensile and compressive module of the warp direction are slightly higher than those of the weft direction, while the tensile and compressive strenghth of the warp direction are significantly higher than those of the weft direction. Tensile and compressive failure modes of the material in the warp and weft direction are significantly different. In case of tension, the waved warp fibers are pulled out, and the straight weft fibers are split. In case of compression, the straight weft fibers are broken, and the waved warp fibers buckling happen. The material shows high shear deformation capacities in both the in-plane and out-of-plane directions. Besides, a formula for estimating the tensile modulus of the 2.5D material was proposed based on the rule of mixtures of unidirectional composites. Based on the microstructure characteristics of the material, a unit cell containing warp and weft yarns was used as a representative volume unit to establish the finite element model, and the meridional modulus of the 2.5D woven composite was predicted. The prediction results are in good agreement with the experimental results. This study can provide some guidance for the development of the 2.5D quartz fiber/bismaleimide composites.