Novel Designs for Interfacial Mechanical Property Enhancement and Characterization of Dissimilar Materials and Structures

不同材料和结构的界面力学性能增强和表征的新设计摘要现代工程系统越来越多地由联合收割机结合两种或多种材料以提高性能的材料制成。通常，失效发生在材料界面或连接处，由于材料性质不匹配。因此，在不同材料之间的界面处的界面强度的准确测量对于这些新材料的材料开发和工程应用是至关重要的，范围从纳米尺度到宏观尺度。 然而，由于双材料界面处存在特殊的“应力奇异性问题”，现有的界面力学测量方法往往导致数据失效。为了准确测量不同材料的固有界面力学性能，本项目提出了新的试样设计，通过综合分析，数值和实验研究。一个初步的设计，灵感来自树木的形状和力学，开发，以获得最少的应力奇异性在双材料的角落，大多数工程材料组合。 新的设计不仅提高了异种材料接头的传力能力，而且得到了更合理的界面强度评估。对于凸聚碳酸酯-铝和PMMA-铝接头，静态极限拉伸载荷增加了81%，而总材料体积减少了至少15%，比传统的对接试样具有严重的自由边缘应力奇异性。 因此，主要研究者和他的研究小组成员计划开发一个更广泛的研究计划，界面力学性能的增强和评价。具体而言，目标是：1）测量新型界面接头在动态载荷下的载荷传递能力的改善; 2）进行轴对称试样设计，用于静态界面拉伸测量。拟议活动的智力价值在于为材料力学中的一个长期问题提出一种新的解决方案。树形的力学原理被用来设计新颖的关节标本。 该项目将提供一个成功的生物灵感设计的例子，以提高科学和技术的理解，即，大自然可以为某些技术难题提供有效的解决办法。由于异种材料界面/接头和失效广泛应用于航空航天、汽车、生物医学、民用、国防、电子、材料和机械工程领域，因此拟议研究的影响将非常广泛。 因此，该项目的研究成果将对信息技术、纳米技术、材料和制造以及民用基础设施非常有益。其他更广泛的影响包括为一名女博士生提供支持，并与国家实验室建立研究伙伴关系。

Novel Designs for Interfacial Mechanical Property Enhancementand Characterization of Dissimilar Materials and StructuresAbstract Modern engineering systems are increasingly made of materials that combine two or more materials for improved performance. Generally, failure occurs at the material interfaces or joints due to material property mismatch. Therefore, accurate measurement of interfacial strength at the interface between dissimilar materials is critical for material development and engineering applications of such new materials, ranging from nano-scale to macro-scale. However, current methods for interfacial mechanical measurement lead to invalid data because of a special "stress singularity problem" at the bi-material interface. In order to accurately measure the intrinsic interfacial mechanical properties of dissimilar materials, this project presents novel specimen designs through an integrated analytical, numerical and experimental investigation. A preliminary design, inspired by the shape and mechanics of trees, was developed to obtain the least stress singularities at bi-material corners for most engineering material combinations. The new design not only improves the load transfer capacity of dissimilar material joints, but also yields more reasonable interfacial strength evaluation. For convex polycarbonate-aluminum and PMMA-aluminum joints, the static ultimate tensile load increased up to 81% while the total material volume reduced by at least 15% over that of traditional butt-joint specimens with severe free-edge stress singularities. Hence, the principal investigator and his research group members plan to develop a broader research program for interfacial mechanical property enhancement and evaluation. In particular, the objectives are to: 1) measure the improvement of load transfer capability of the novel interfacial joint subjected to dynamic loading 2) conduct axisymmetric specimen designs for static interfacial tensile measurements. The intellectual merit of the proposed activity consists in presenting a new solution to a long-term problem in mechanics of materials. The mechanics principles underlying tree shapes are used to design novel joint specimens. The project will provide a successful example of biologically inspired design to enhance scientific and technological understanding, i.e., nature may provide efficient solutions for certain difficult technological problems. The impact of the proposed research will be very broad since dissimilar material interfaces/joints and failure are widely employed in aerospace, automobile, biomedical, civil, defense, electronic, material and mechanical engineering fields. Therefore, the research results from this project will be very beneficial to information technology, nano technology, materials and manufacturing and civil infrastructure. Other broader impacts include providing support for a female doctoral student and developing research partnership with national laboratories.