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

Vanderbilt University, Nashville TN

Investigators

Abstract

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