EFFECTS OF DISPLACEMENT VELOCITY TO FRACTURE OF LAMINATE

研究了含边缘脱层的层合梁在脉冲载荷作用下的受力情况。通过测量引起分层生长的冲击载荷，得到了最大冲击载荷、初始分层长度和分层生长距离之间的关系。结果表明，在初始裂纹长度范围内存在一个不易发生分层扩展的区域。在有限元分析中，假设裂纹面相互接触，采用局部柔度法得到能量释放率。结果表明，裂纹长度存在不易发生分层的区域，与实验结果一致。因此，通过数值分析可以很好地预测分层生长。本文还研究了含有初始分层的层合梁和含有盘状分层的层合板的自由振动。基本假设是裂缝面上下的梁或板的部分是相互接触的。对分层长度（或圆盘状裂纹直径）、分层位置和组成材料弹性模量对振动特征频率和振型的影响进行了分析和实验。分析了相互接触力的分布。理论与实验结果吻合较好，验证了本文所建立的分析模型的正确性。本研究提供了一种方法，以确定长度（或直径）的分层和他们的位置，从测量振动行为的变化。

Laminated beams containing an edge delamination subjected to impulsive loads are studied. By measuring the impact loads that cause delamination growth, relations between the maximum impact load, initial delamination length and the distance of growth of the delamination are obtained. As a result, it is found that there exists a region of initial crack length for which delamination growth cannot occur easily. Finite-element analyses are also carried out, where by assuming the mutual contact of crack faces, energy release rates are obtained by the local compliance method. It is shown that there exists the region of crack length for which delamination cannot easily occur, agreeing with experimental results. Therefore it is concluded that the delamination growth can be predicted well from numerical analyses.Study is also made for free vibrations of both a laminated beam containing an initial delamination and a laminated plate containing a disk-shaped delamination. Basic assumption is that parts of a beam or plate above and below the crack faces are contacting one another. Analyses and experiments are carried out for the effects of the delamination length (or the diameter of a disk shaped crack), the location of delaminations and elastic moduli of constituent materials on the characteristic frequencies and modes of vibrations. Distributions of mutual contact forces are also analyzed. Theoretical and experimental results agree well, which validates the analytical models assumed in our present study. This study gives a means to determine the length (or diameter) of delaminations and their locations from the measurement of the change of vibration behaviour.