【作者】 阮江涛；

【导师】 王世斌；

【作者基本信息】 天津大学 ， 固体力学， 2012， 博士

【摘要】 本文的主要工作是对缝合和未缝合复合材料层合板在低速冲击后压缩实验研究与数值分析。在实验研究中,先对散斑干涉条纹图滤波处理和相位测量进行了研究,然后利用载波电子散斑干涉法(electronic speckle pattern interferometry,ESPI)测量了含冲击损伤缝合和未缝合层合板试件压缩时离面位移场。在数值分析中,分析了不同冲击损伤对层合板压缩变形的影响,以及考虑了缝线对含冲击损伤层合板压缩离面位移的影响。电子散斑干涉法具有全场性、非接触、测量灵敏度高等优点,对试验环境要求较低,广泛应用于对物体表面微小的位移等物理量的精密测量。针对散斑干涉条纹图具有很强颗粒噪声的特点,提出了改进的各向异性扩散方程ESPI条纹图去噪方法。根据去相关最优停止准则,确定了最优迭代次数。ESPI条纹图相位场直接反映物体变形信息,研究了条纹中心线法、相移法、载波法和单幅ESPI干涉条纹图提取相位的不同方法。对散斑干涉条纹图去噪和相位测量方法的研究,提高了实验测试精度。层合板受低速冲击后的压缩变形分析对于结构的强度有非常重要的意义。本文利用载波ESPI方法测量含冲击损伤和无损伤缝合和未缝合层合板[03/903]S四种不同试件在整个压缩过程中离面位移的变化过程。实验结果表明,缝合增加了板沿厚度方向的约束,提高了板的层间性能,从而有效地阻止或抑制由分层损伤引起局部离面位移的产生,提高层合板的抗损伤容限。冲击损伤一方面使层合板易产生离面位移,另一方面由于较大的冲击分层损伤,使层合板面内刚度下降较大,易于整体变形的发生。利用有限元方法分析了不同冲击损伤对层合板压缩变形的影响,冲击点背面处离面位移随着冲击能量、最大冲击力和分层面积、长度、宽度的增加而增加。考虑了缝线对含冲击损伤层合板压缩离面位移的影响。随分层面积的增大,缝线抑制或减小层合板离面位移越明显。同时,将有限元计算结果与部分实验结果进行了比较,结果表明两者变形规律基本一致。更多还原

【Abstract】 The main works of this paper are to research the compressive deformation after impact loading of stitched and unstitched composite laminates using experimental method and numerical analysis. In the experiments, the filtering methods and phase measurement techniques for speckle fringe patterns are studied firstly, and then the carrier electronic speckle pattern interferometry (ESPI) is applied to measure the out-of-plane displacement field on stitched and unstitched composite laminates with impact damages under compressive loads. In the numerical simulations, FEM is used to investigate the effect on the compressive deformation of laminates with different impact damages. Meanwhile, stitch line that has influence on the out-of-plane displacement for laminates with impact damages under compression are taken into account.Electronic speckle pattern interferometry is a whole-field, non-contact, high accuracy measurement technique, which can be used under poor testing environment. It is well-known for micro deformation precision measurement of object surface. Due to the serious speckle grain random noise in speckle interferometry, an improved anisotropic diffusion is presented for ESPI fringe pattern denoising in this paper. Moreover, the optimal iteration times are determined based on decorrelation optimal stopping criteria. As the phase field of ESPI fringe patter reflects the deformation of object directly, the fringe-centerline method, phase shifting technology, carrier method and phase extraction method of an ESPI fringe pattern are studied. The results are helpful for improving the experimental measurement precision. It is of great useful for understanding the strength of engineering component to know the compressive deformation of laminate after impact. In this work, carrier-ESPI method is applied to measure the out-of-plane displacement of the stitched and unstitched laminates [03/903]S with impact damages or without damage.The experimental results show stitching improve the through-the-thickness constrains and the inter-laminar performance, which can effectively prevent or restrain the growth of out-of-plane displacement because of delamination damage, and can improve the damage tolerance of laminate. On one hand, the impact damage prone to produce the out-of-plane displacement of laminate. On the other hand, the impact damage leads to the dramatic decrease for in-plane rigidity of laminate. Therefore, the global deformation arises easily.Additionally, FEM is used to research the deformation behavior of laminates with different impact damages. The out-of-displacement of a point on the impact back surface corresponding to the impact axis is increase with the increasing of impact energy, maximum impact force, delamination area, length, width, et al. The effects of stitching for laminates with impact damages are also taken into account. With the increasing of delamination area, the effects of stitching which can prevent or restrain the out-of-plane displacement growth appear apparently. Meanwhile, the FEM results are compared with experimental ones. The results indicate that the both deformation feature tends generally to be consistent with each other.更多还原