Physical Mechanisms Governing the Intersonic and Supersonic Decohesion of Bimaterials: Effects of Interfacial Strength, Loading Rate and Confining Pressure

将对与双材料界面和简单单向复合材料的高动态解粘相关的物理现象进行分析研究。该项目的具体目标是建立在各种状态(亚音速、跨音速和超音速)下动态双材料退缩的必要条件，并描述相关的物理现象。为了实现这些目标，将选择允许界面强度、围压和界面上的机械性能(最重要的是波速)不匹配的材料组合和加工技术。此外，将选择能够提供一定范围的撞击速度的加载配置。将进行分析研究，以建立一个理论框架，通过该框架，可以用适当的断裂参数来鉴定实验观察到的以瞬时、跨声速和超音速剪切为主的机械场。还将研究由观测到的大范围摩擦接触产生的热场和相关的能量耗散。动态加载或扩展界面裂纹附近的变形场和热场的实验测量将使用超高速光学和热像诊断技术实时进行。形变场将使用高速摄影结合两种光学技术：相干梯度传感(CGS)和动态光弹性来表征。用最新研制的高速红外相机测量了剪切为主的跨声速和超音速界面裂纹附近的温度场，以研究局部能量耗散机理。

An analytical study will be conducted of the physical phenomena associated with highly dynamic decohesion of bimaterial interfaces and simple unidirectional composites. Specific goals of the project are to establish the necessary conditions for dynamic bimaterial decohension in various regimes (subsonic, intersonic, and supersonic) and to characterize the associated physical phenomena. To accomplish these goals, material combinations and processing techniques will be chosen that allow for the variation of interfacial strength, confining pressure and mismatch of mechanical properties (most importantly wave speeds) across the interface. In addition, loading configurations will be selected that can provide a range of impact velocities. Analytical studies will be undertaken to develop a theoretical framework by which the experimentally observed transient intersonic and supersonic shear dominated mechanical fields can be qualified in terms of appropriate fracture parameters. Thermal fields resulting from the observed large scale frictional contact and the associated energy dissipation will also be investigated. Experimental measurements of the deformation fields and thermal fields in the vicinity of a dynamically loaded or propagating interfacial crack will be performed in real time using ultra-high speed optical and thermographic diagnostic techniques. The deformation fields will be characterized using high speed photography in conjunction with two optical techniques: Coherent Gradient Sensing (CGS) and dynamic photoelasticity. Temperature fields near shear dominated intersonic and supersonic intrfacial cracks willb measured using a recently developed high speed infrared camera in order to study local mechanisms of energy dissipation.