叠层密度梯度材料的静动态力学行为及失效机理研究

Laminated density gradient material is a kind of multi-interface composite designed by a variety of dissimilar metals arranged according to their density. This laminated structure has superior mechanical properties compared to homogeneous material and it could meet the needs of advanced material in areas such as aerospace and national defense military. In present research, laminated density gradient material is fabricated by explosive welding using material and mechanical approaches, in which the macro-mechanical properties of the laminated composites, especially the dynamic mechanical behavior, damage evolution and failure mechanics under impact loading are focused on research. Firstly, SEM, TEM and XRD tests are applied to study interface microstructure evolution; Secondly, tensile, split Hopkinson bar and impact experiments have been performed in the laminated composites to show the static, quasi-static and dynamic mechanical properties, e.g. strength, ductility, fracture, Hugoniot elastic limit(HEL) and spall strength; Lastly, thought building the relation of mechanical properties and material mechanics, the plastic deformation mechanics and failure behaviors are characterized to give an evaluation for the service performance of laminated density gradient material under extreme circumstances. The investigations in this project are expected to show some guidance in preparing laminated composites with superior mechanical properties to meet the needs of national defense military and other industry fields.

叠层密度梯度材料是由多种异性金属按密度梯度排列叠加形成的一种多界面复合材料，这种层状强韧化结构具有均质材料无法比拟的力学性能,能满足航天、国防领域对先进材料的要求。项目以爆炸焊接为手段，从材料学角度，辅以严格的力学计算，制备叠层密度梯度材料，重点分析其宏观力学特性,特别是动态力学性能以及冲击加载下损伤演化、失效机理。首先，利用SEM、TEM、XRD等表征其界面处的微观结构，分析异性界面结合的形貌、组织演化规律；然后，通过静态、准静态以及动态加载实验，测试叠层密度梯度材料在不同速率加载条件下的力学特性，包括：强度、韧性、断裂、Hugoniot弹性极限、层裂等；最后，通过建立宏观力学特性和微观机理的直接联系，揭示叠层密度梯度材料的变形机制、失效机理，评估其在极端环境下的服役可靠性，为其在国防、生产中应用奠定基础。

叠层金属复合板由于其多组元性能以及多界面强韧化特点，是一类兼具功能和结构双重属性工程材料，能满足航天、国防领域对先进材料的要求。爆炸焊接是生产叠层金属复合板的重要方法之一。本项目通过理论设计、实验手段以及数值模拟，对叠层复合板的制备、表征和静、动态力学行为开展了细致深入的研究。主要研究内容包括如下：提出两种适用于薄板的爆炸焊接方法，水下爆炸焊接以及铝板驱动式爆炸焊接，并给出了详细的装置图以及焊接参数；设计单轴拉伸、三点弯曲、预制缺口三点弯曲以及摆锤冲击试验，设计小型试样和夹具，对层合板的应力-应变曲线、拉伸强度、弯曲强度、冲击功等进行详细的研究；从材料学和力学角度，对叠层复合板强韧化机理进行分析。重要结果如下：利用爆炸焊接制备钛-铜，镁-铜以及镍-铜多层板，微观结构显示典型均匀波状界面，无缺陷和空隙；静、动态力学实验表明，各组层合板拉伸强度、弯曲强度、断裂强度以及抗冲击能力均高于基体材料以及基于强度混合法则推算出的理论强度；微观结构、断口形貌以及裂纹轨迹分析显示，层合板强韧化机理在于爆炸焊接产生的加工硬化以及层状结构独特的裂纹阻滞能力。裂纹阻滞能力主要表现为裂纹萌生阻滞和裂纹偏转。在裂纹传递过程中，相较于均质材料，层合板通过裂纹的阻滞和方向偏转显示出了优秀的裂纹抑制能力。本项目的研究成果对于深入理解叠层金属复合板的强韧化机理，更好的为其在工程中应用奠定了基础，同时为同类型金属复合材料的设计和开发提供指导。总体来说，基本完成了本项目预定研究内容，研究结果丰富了爆炸焊接以及叠层复合板的研究。