复合材料蜂窝夹芯板结构损伤及其修理后仿真分析

发布时间：2018-10-08 14:09

【摘要】：结构轻量化是航空航天发展的永恒主题,复合材料蜂窝夹芯板凭借比强度高、比刚度大、抗失稳能力强等优越性能,被广泛应用在飞机的主、次承力结构。在制造、装配和使用过程中,复合材料蜂窝夹芯板容易受到冲击等损伤并需要进行修理。夹芯板结构修理后可能在复材层合板、粘接胶层和蜂窝芯层出现不同类型的损伤,修理结构的损伤预测和强度评估已成为复合材料研究中急需解决的问题。本文针对复合材料蜂窝夹芯板及其典型的胶接挖补修理结构,通过试验结合仿真分析的方法,开展渐进损伤分析和强度预测研究。针对复合材料层合板胶接挖补修理结构,基于复材层合板CDM模型和胶层CZM模型建立三维渐进损伤分析的有限元仿真模型,基于Hashin准则编写UMAT程序实现复材纤维和基体的损伤模拟。仿真结果在胶层、母板和补片的失效模式,以及极限强度方面与试验结果相符,为蜂窝夹芯板修理结构仿真分析提供了层合板部分的有效模型。针对典型Nomex?蜂窝芯层进行平压和剪切力学性能试验,获得了等效刚度、强度等材料参数,总结蜂窝芯层损伤和变形过程分为“弹性-压溃/剪溃-皱曲-密实/撕裂”4个阶段,发现蜂窝芯层破坏后依然保留部分承载能力,剪切/平压的剩余强度约占极限强度的40%~45%。基于试验结果对Sandwich夹芯板理论中的蜂窝等效模型进行改进,引入蜂窝压溃剪溃损伤和损伤后剩余强度,建立了有限元损伤分析模型。采用Besant准则作为蜂窝损伤判据,分别编写USDFLD和UMAT程序实现刚度突然退化和渐进退化的两种损伤演化规律。通过蜂窝夹芯板三点弯曲的仿真与试验对比,验证了模型的可靠性和高效性。最后针对复合材料蜂窝夹芯板典型胶接挖补修理结构,建立三维渐进损伤分析的有限元模型并进行仿真计算。分析发现夹芯板修理后强度明显恢复,修理结构在侧压载荷下未修理区域发生局部屈曲,蜂窝和复材损伤并扩展,导致结构最终失效。模型仿真结果在失效模式和极限载荷方面与试验吻合较好。修理参数仿真分析表明,随着补片附加层厚度和搭接宽度增加,结构由于附加弯矩提前失稳,极限载荷降低;挖补角度和补片搭接宽度越小,胶层内部剪应力越高。建议修理设计时应避免局部刚度改变过大而对结构承载造成的不利影响。
[Abstract]:Structural lightweight is the eternal theme of aerospace development. Composite honeycomb sandwich panels are widely used in aircraft main and secondary load-bearing structures due to their high specific strength, high specific stiffness, strong ability to resist instability, and so on. During manufacture, assembly and use, composite honeycomb sandwich panels are vulnerable to impact damage and need to be repaired. Different types of damage may occur in laminated laminates adhesive layers and honeycomb core layers after repair. The damage prediction and strength evaluation of the repaired structures have become an urgent problem in the study of composite materials. In this paper, progressive damage analysis and strength prediction are carried out for composite honeycomb sandwich panels and their typical glued repair structures. The finite element simulation model of 3D progressive damage analysis is established based on CDM model and CZM model of composite laminates. Based on Hashin criterion, UMAT program is compiled to simulate the damage of composite fiber and matrix. The simulation results are consistent with the test results in the failure mode of rubber layer, motherboard and patch, and the ultimate strength, which provides an effective model for the simulation analysis of honeycomb sandwich panel repair structure. For typical Nomex? The material parameters such as equivalent stiffness, strength and other material parameters are obtained. The damage and deformation process of honeycomb core layer is divided into four stages: elastic-crushing / shear-wrinkling, compacting / tearing. It is found that the honeycomb core layer still retains part of the bearing capacity after failure, and the residual strength of shear / flat compression is about 40% of the ultimate strength. Based on the experimental results, the honeycomb equivalent model in Sandwich sandwich panel theory is improved, and the finite element damage analysis model is established by introducing honeycomb crushing damage and residual strength after damage. The Besant criterion is used as the criterion of honeycomb damage and the USDFLD and UMAT programs are written to realize the two kinds of damage evolution laws of sudden and progressive degradation of stiffness respectively. The reliability and efficiency of the model are verified by comparing the simulation and experiment of honeycomb sandwich panel with three-point bending. Finally, the finite element model of 3D progressive damage analysis is established and simulated for the typical adhesive repair structure of composite honeycomb sandwich panel. It is found that the strength of sandwich panels recovers obviously after repair and local buckling occurs in the unrepaired area of the repaired structure under lateral pressure. The damage and expansion of honeycomb and composite materials lead to the ultimate failure of the structure. The simulation results agree well with the test in failure mode and limit load. The simulation analysis of repair parameters shows that with the increase of the thickness of the additional layer and the width of the lap, the ultimate load of the structure decreases due to the instability of the additional bending moment, and the smaller the mending angle and the width of the lap, the higher the internal shear stress of the adhesive layer. It is suggested that the local stiffness change should be avoided during the repair design and the adverse effect on the bearing capacity of the structure should be avoided.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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