Modeling of effects of adhesive interlayers on contact-induced radial cracking in brittle coatings on substrates
- PDF / 157,096 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 92 Downloads / 208 Views
Jong Ho Kim and Do Kyung Kim Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Yusong, Taejon 305-701, Korea (Received 12 December 2002; accepted 27 March 2003)
The effects of soft adhesive interlayers on contact-induced radial cracking in brittle coatings on supporting substrates were investigated recently. A semiempirical equation for the critical load to initiate radial cracking was derived, which used three fitting parameters obtained by comparison with the finite element results. An analytical model is derived in the present study to illustrate the effects of adhesive interlayers. This is achieved by adopting the analogy between the coating/substrate system and a plate on an elastic foundation. In the presence of an adhesive interlayer, the interlayer/substrate bilayer is treated as the effective elastic foundation. The effective modulus of foundation for the bilayer is derived, and the solution for coating/interlayer/substrate systems can be obtained from the existing solution for coating/substrate systems by replacing the modulus of foundation. Specific results are calculated for critical loads to initiate radial cracks in silicon coatings bonded by adhesive interlayers of different materials and thicknesses to glass substrates. The present analytical solution provides an alternative other than the existing semiempirical equation in predicting the effects of adhesive interlayers.
I. INTRODUCTION
Adhesive interlayers have been used extensively to join brittle layers to supporting substrates. The applications include dental crowns, car windshields, and other laminate structures. Because adhesives are soft, they provide damage tolerance by redistributing stresses and confining damage within individual brittle layers.1,2 However, when the top surface of the system is subjected to concentrated loading, the soft adhesive layer enhances flexural stresses in the brittle layer, which, in turn, facilitates radial cracking at the undersurface of the brittle layer.3 This radial cracking has been identified as a primary source of failure in dental crowns and car windshields.4–6 Hence, to maintain the functionality and reliability of laminate structures, it is essential to understand how the adhesive interlayer influences the critical load for initiating contact-induced radial cracking at the undersurface of the brittle coating on a supporting substrate. The first study of the effects of adhesive interlayers was performed by Chai and Lawn.7 A special case of two glass plates bonded by an epoxy adhesive was examined, and a semiempirical equation was formulated to express the functional dependence of the critical load for radial cracking on adhesive thickness and modulus. While Chai and Lawn’s equation was limited to the case where the coating and the substrate were the same material, Kim J. Mater. Res., Vol. 18, No. 6, Jun 2003
http://journals.cambridge.org
Downloaded: 17 Apr 2015
et al. extended the analysis to the case where the coating and the substrate were made
Data Loading...
