摘要
纤维增强复合材料(FRP)由于其优越的材料性能,在航空航天、汽车、土木工程等领域得到越来越广泛的应用。同时纤维复合材料在实际使用过程中也遇到了各种各样的问题,其中复合材料层合板的连接失效与低速冲击作用下复合材料层合板分层就是其中的两个重要方面。
本文采用粒子群算法对复合材料层合板销钉连接处分层挤压强度进行优化。首先采用三维有限元对连接模型进行应力分析,为尽可能模拟真实情况,考虑销钉与板之间的三维接触,然后采用修改的Ye分层准则对分层挤压强度进行预测,接着将预测的结果与文献中的实验值比较,以验证分层挤压强度计算的有效性。为了避免ANSYS中自带优化算法对初值敏感且易陷入局部最优的缺陷,借助粒子群算法与ANSYS之间的接口程序,采用全局智能优化算法(粒子群算法)对初始分层强度进行优化,在给定的约束条件下,寻找在相应的设计空间中最佳的设计变量值,以得到最优的分层挤压强度。该方法及结果可为实际工程中复合材料接头的设计提供有益的参考。
本文采用粘聚区域模型,对金属/纤维层合板在低速冲击载荷作用下的分层情况进行了研究。粘聚力模型对裂纹的模拟具有它独特的优势:一是该模型不需要预先假设初始缺陷;二是在计算过程中随着裂纹的扩展,该方法不需要重新对结构进行网格划分。首先为了考察粘聚区域模型对分层开裂模拟的有效性,本文对纤维层合板在低速冲击载荷作用下,层合板的分层进行了模拟。结果显示该模型可以对分层的扩展方式、分层形状进行有效地预测。在此基础上,本文研究了低速冲击载荷作用下,纤维/金属层合板的分层情况,并将其与纤维层合板进行了比较。同时本文还调查了等密度条件下,不同铺层结构和金属含量对纤维/金属分层的影响。
Fiber Reinforced Plastics (FRP) is widely used in aerospace industry, automobile area and civil engineering, owing to its excellent properties, such as high specific strength and modulus and its designability. But meanwhile, various problems come out during the application of FRP in the real engineering structure. Two important issuess are the failure of composites joints under bearing load and the delamination of composite laminates under low-velocity impact.
One aim of this paper is to develop a method that combines Finite Element Analysis (FEA) and evolutionary algorithms in predicting and maximizing the delamination bearing strength of composite pin joints. First, based on three-dimensional contact analysis around the vicinity of pin joints, the delamination bearing strength of joints is predicted using the modified Ye-delamination criterion. Then, the maximization of the strength is studied. To overcome the disadvantage that the optimization algorithm incorporated in ANSYS is both sensitive to the initial value and liable to get involved in the local optimum, a global intelligent optimization algorithm-Particle Swarm Optimization(PSO) is used to optimize the delamination bearing strength. The optimum design variables and delamination bearing strength are achieved under the given constraint condition and the influence of pin diameter on the optimum delamination bearing strength is investigated. The method and results in this paper can offer beneficial reference to the design of composite pin joints in the practical engineering.
In this paper, cohesive zone model is used to study the delamination of FMLs under low-velocity impact. The model owns two main advantages: one is that no initial crack is needed to be assumed; another is that there is no need to remesh the model during the crack propagation. First, to validate the cohesive zone model in dealing with delamination of composite laminates, the delamination simulation is carried out under the low-velocity impact and a relative good agreement is achieved with the experimental data. Next, the delamination of FMLs is investigated under low-velocity impact and the results are compared with that of composite laminates. What's more, the effects of stacking structures and metal ratios towards the delamination of fiber/metal laminates are studied.
引文
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