1. Definition of nanocomposites Nanocomposites are a novel class of composite materials whose reinforcements have dimensions in the range of 1-100 nm. Although nanoscale reinforcements (or nanofillers) of nanocomposites have different kinds of fillers such as nanofibers, nanowires, nanotubes and nanoparticles etc, their mechanical behaviors have some common features. Figure 1 shows a potential use of nanocomposites as multifunctional materials. Since many important chemical and physical interactions are governed by surfaces and surface properties, and nanoscale reinforcements have a large surface area for a given volume, nanocomposites are ideal multifunctional materials. For nanotube-reinforced materials, coupled mechanical and electric properties of nanotubes can be used for very small-scale health monitoring.

FACULTY POSITION
 
 
MECHANICAL ENGINEERING
COLLEGE OF ENGINEERING
UNIVERSITY OF CALIFORNIA, SANTA BARBARA
 
 

Recently, I am interested in the interface between two different masses. But, I don’t know how to characterize the interface between them, especially the adhesive strength and the mechanics model.

Finite element stress analysis and corner optimization of a tree-steel railing interface/joint (Mattheck, 1998) showed that the naturally formed tree/railing joint was very effective in reducing stress concentration. Using this principle, we designed and tested convex interfacial joints of dissimilar engineering materials, and find that these new joints will significantly increase ultimate failure load and even reduce material volumes.  Click here to read two related papers (a. Xu, et al., Experimental Mechanics, 2004; b. Wang and Xu, Mechanics of Materials, 2006).

This high-speed photography image shows a mode I crack (representing by a symmetric photo elasticity fringe pattern) is approaching a weak interface in a brittle polymer (Homatel-100). The crack tip speed is around 300-400 m/s. There will be three possibly situations for dynamic interfacial failure mode transitions : 1) crack kinks at the interface, 2) crack directly penetrates the interface and 3) interface debonding occurs before the incident crack reaches the interface. Which case will occur?