EFFECTS OF DISPLACEMENT VELOCITY TO FRACTURE OF LAMINATE

研究了在冲击载荷作用下含边缘脱层的层合梁。通过测量引起脱层扩展的冲击载荷，得到了最大冲击载荷、初始脱层长度与脱层扩展距离之间的关系。结果发现，初始裂纹长度存在一个不易发生分层扩展的区域。通过假设裂纹面相互接触，采用局部柔度法得到了能量释放率，并进行了有限元分析。结果表明，裂纹长度存在一个不易发生分层的区域，与实验结果一致。本文还研究了含初始脱层的层合梁和含盘状脱层的层合板的自由振动问题。基本假设是梁或板在裂纹面上方和下方的部分相互接触。分析和实验了分层长度（或圆盘状裂纹直径）、分层位置和组成材料的弹性模量对振动特征频率和振型的影响。还分析了相互接触力的分布。理论和实验结果吻合良好，这验证了我们在本研究中假设的分析模型。本研究给出了一种方法，以确定长度（或直径）的脱层和他们的位置从测量的振动行为的变化。

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.