The Challenge of Attaching Dissimilar Materials - Structural Interfaces and Attachments in Biology - page 2

Chapter 1
The Challenge of Attaching Dissimilar Materials

Stavros Thomopoulos, Victor Birman, and Guy M. Genin

1.1 Introduction

Interfaces between dissimilar structural materials have existed since our first
multicellular ancestors evolved. Attachments and joints between dissimilar materials
are commonly found throughout nature, physiology, and engineering. A difference in
material properties may be realized as either a step-wise change from one material to
the other or as a gradual variation across a short distance, as is the case with
functionally graded interfaces. A mismatch between material properties at the inter-
face raises unique problems related to strength, stiffness, and fracture behavior of the
attachment. For example, the difference in stiffness between bone and tendon, where
the modulus of elasticity varies by almost two orders of magnitude over a short
distance, could cause severe problems at the tendon-to-bone attachment; the potential
stress concentrations are alleviated in part through gradation of properties at the
interface. Fracture along the bondline between a metal hip replacement and bone is
driven by a mismatch in the properties of these materials. Issues related to interfaces
between dissimilar materials arise in many engineering applications as well. For
example, high thermal stresses are problematic in electronic packaging along the
junction between the chip and the substrate due to the different thermal expansion
coefficients of the two materials.

S. Thomopoulos ( * )
Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO, USA
e-mail: [e-mail]
V. Birman
Engineering Education Center, Missouri University of Science and Technology, Rolla, MO, USA
e-mail: [e-mail]
G.M. Genin
Department of Mechanical Engineering and Materials Science, Washington University
in St. Louis, St. Louis, MO, USA
e-mail: [e-mail]