2.5D机织复合材料压缩性能实验与数值模拟

为了研究2.5D机织复合材料的压缩损伤和失效机制,验证双尺度渐进损伤有限元数值模拟方法的有效性,对这类复合材料分别沿经纱方向和纬纱方向进行了准静态压缩实验,获得了其相应的应力-应变曲线,并测定了材料的初始弹性模量和极限强度。在此基础上,利用双尺度渐进损伤有限元数值方法模拟分析了材料的压缩应力-应变响应和损伤演化行为,取得了与实验吻合较好的模拟结果。结果表明:2.5D机织复合材料在纬向压缩下的主要失效模式是纬纱的轴向压溃与断裂,可获得相对较高的压缩强度;但在经向压缩下,经纱因弯曲会承受附加弯矩作用,从而对周围基体造成挤压,故在经纱轴向断裂之前容易出现经纱之间基体的压溃和纱线之间的分层开裂,使强度降低,不利于发挥纤维的承载优势。

Experiment and numerical simulation on compressive properties of 2.5D woven fabric composites

To investigate the damage and failure mechanisms of 2.5D woven fabric composites under compression, and verify the effectiveness of the finite element numerical simulation method with a two-scale, progressive damage model, quasi-static compression experiments were conducted on both warp and weft directional specimens to obtain the corresponding stress-strain curves. And the initial elastic modulus and ultimate strength of materials were measured. On this basis, the compressive stress-strain responses and the damage evolution behavior were simulated using the two-scale, progressive damage finite element numerical method. The results from both experiment and simulation show good agreements, and indicate that the main failure mode of 2.5D woven fabric composites in weft directional compression is the axial crush and fracture of weft yarns, from which relatively higher strength is obtained. Meanwhile, additional bending moment is added to the warp yarn under warp directional compression due to bending, which causes extrusion on surrounding matrix. Therefore, matrix fracture and delamination cracking between neighboring warp yarns easily occur before the axial fracture of warp yarns, which are not conducive to utilize the advantage of fibers in bearing load, and result in relatively lower strength.