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大开口复合材料层合板强度破坏研究

STRENGTH ANALYSIS OF FIBER REINFORCED COMPOSITE LAMINATES WITH BIG CUTOUTS

  • 摘要: 复合材料层合板的各向异性及非均质,使得复合材料层合板内部的破坏形式非常复杂.在复合材料结构的设计中,为满足制造及使用功能上的需求,在复合材料层合板承力结构件上不可避免地需要设计各种开口.然而,含大开口复合材料层合板的强度破坏问题变得更为复杂,使得现有的强度理论面临新的挑战.针对碳纤维增强复合材料大开口层合板受单向拉伸载荷作用下的强度破坏问题进行了数值分析和实验研究.首先,根据Hashin准则和刚度退化模型,对含不同圆形开口尺寸的010单向铺层、0/905和±455正交铺层的层合板,进行了单向拉伸载荷作用下渐进失效的数值模拟分析,获得了对应结构的极限载荷和破坏模式.在此基础上,采用数字图像相关方法,进行复合材料大开口层合板强度破坏的实验研究.研究结果表明,大开口复合材料层合板在单向拉伸加载下主要呈现脆性破坏形式,破坏起始位置处于应力集中区.此外,破坏强度和失效模式与复合材料铺层方式和开口尺寸大小密切相关.其中±455铺层的开口层合板承载能力最弱,分层破坏最严重.开口尺寸越大,结构的极限载荷值越低.同实验测试结果相比,数值模拟对复合材料层合板的损伤失效分析略显不足,往往很难全面分析复合材料层合板破坏失效过程中的各种因素的影响.

     

    Abstract: As a heterogeneous anisotropic material, the failure behavior of composite laminate is very complicated. In order to meet manufactural and functional requirements, it is unavoidable to have cutouts on primary composite structures. However, it makes the failure criterions face new challenges due to the more complicated failure processes of composite laminates with big cutouts. In this paper the strength analysis of carbon fiber reinforced composite laminate with big cutout under unidirectional tension is studied by numerical analysis and experimental tests. Firstly, consider the composite laminates with different layups, such as010 unidirectional laminate,0/905 and±455 cross-ply laminates, and different circle cutouts, Hashin criterion and stiffness degradation model are applied to analyze the progressive failure process under unidirectional tension by numerical simulation to obtain the ultimate load and failure mode for each laminate. Furthermore, according to the numerical models, experiments are carried out based on 3D digital image correlation (DIC) method. Results show that the failure mode of fiber reinforced composite laminate with big cutout under unidirectional tension is a typical brittle fracture, and the crack onset happens to the high stress concentration area. In addition, the failure mode and crack propagation strongly depend on the ply sequences and the cutout size. Therefore, comparing to others,±455 cross-ply laminate with big cutout has the lowest ultimate load for its serious delamination failure mode. The bigger of the cutout size, the lower of ultimate load. After comparison of experimental and numerical results, it is concluded that the numerical simulation for strength analysis of composite laminate should be improved by further developed criterions.

     

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