Fracture Mechanics of Interfaces of Laminates Subjected to Thermal Shock or Low Velocity Impacts

考虑了含有内部圆盘状界面裂纹的层合板。本文的主要目的是推导能量释放率，它是决定界面裂纹扩展条件的最重要的参数。首先，我们考虑了层合板受到热冲击的情况。假设通过例如激光加热突然将恒定热流施加在层合板的顶面上。随着温度的升高，板材通过厚度温度梯度弯曲。已知加热开始后任意时刻t的温度分布。利用这一结果，并将圆盘状裂纹上下两个圆板组成的板的一部分模拟为两个在其边缘铰接的重叠圆板，从理论上确定了层合板的挠度。研究发现，盘状…上方的板材部分由于温度梯度引起的径向压应力，更多的国家会引起局部屈曲。结果表明，由于能量释放率变得很大，这种屈曲将极大地促进分层的扩展。其次，我们考虑了低速冲击下圆盘状界面裂纹的扩展。假设冲击是由一根质量较大的自由下落的刚性柱撞击圆盘状裂纹中心正上方的板面上的点造成的。基于特征函数展开法，从理论上确定了碰撞点的集中力和板的挠度是碰撞瞬间后时间t的函数。通过与实验结果的比较，验证了本文的分析结果。能量释放率也是时间t的函数。结果表明，能量释放率比静载情况下的能量释放率大约3倍。较少

A laminated plate containing an interior disc-shaped interface crack is considered. The main aim of the present research is to derive the energy release rates, which is the most important parameter that determines the condition of interface crack growth.First, we consider the case when a laminated plate is subjected to thermal shock. A constant heat flux is assumed to be suddenly imposed over the top surface of a laminated plate by, for example, a laser heating. As the temperature is raised, the plate is bent by the through the thickness temperature gradients. The temperature distribution at an arbitrary time t after the initiation of heating has already been known. Utilizing this result and modeling the portion of the plate consisting of the two circular plates above and below the disc-shaped crack as two lapped circular plates hinged at their rims, the deflection of the laminated plate is theoretically determined. It is found that the portion of the plate above the disc-shaped delami … More nation causes local buckling due to radial compressive stress induced by the temperature gradients. It is shown that this buckling would greatly promote the growth of delamination, since the energy release rates become very large.Second, we consider the growth of a disc-shaped interface crack by the low velocity impact. The impact is assumed to be made by the strike of a freely falling rigid column with large mass at the point of the plate surface directly above the center of the disc-shaped crack. Based on the characteristic function expansion methods, the concentrated force applied at the point of collision and the deflection of the plate are theoretically determined as functions of the time t after the instant of impact. By comparing the results with experiments, the present analyses are well confirmed. The energy release rate is also derived as a function of time t. It is shown that the energy release rate becomes about three times larger than that for the case of statically applied load. Less