Multiscale Optimization of Joints of Dissimilar Materials in Nature and Lessons for Engineering Applications

In this chapter we review various aspects of biological attachments of dissimilar materials, concentrating on the example of tendon-to-bone attachment, a composite made up of compliant collagen fibers and stiff mineral platelets. The natural optimization of this attachment occurs on several scales, including macroscopic morphology and interdigitation. Macroscopically, interdigitation is analogous to z-pinning in composite joints. Microscopically, functional grading occurs for both the orientation of collagen fibers and the distribution of mineral. Nanoscopic optimization involves the sequencing of mineral deposition within and around the collagen fibrils. The lessons from the tendon-to-bone attachment are pertinent to the attachments of dissimilar materials in engineering. A discussion on possible applications of these lessons in engineering attachments is included in the concluding section of the chapter.