Durability of Adhesive Joints Subjected to Environemntal Stress

Type of Document Dissertation
Author O'Brien, Emmett P
URN etd-09302003-110117
Title Durability of Adhesive Joints Subjected to Environemntal Stress
Degree PhD
Department Chemical Engineering
Advisory Committee
Advisor Name Title
Thomas C. Ward Committee Chair
David A. Dillard Committee Member
Eva Marand Committee Member
Ravi Saraf Committee Member
Richey M. Davis Committee Member
Keywords

* ink
* dielectric spectroscopy
* diffusion
* electrochemical impedance spectroscopy (EIS)
* epoxy
* interface
* water
* sub-critical crack growth
* durability
* environmental degradation
* adhesion
* shaft-loaded blister test

Date of Defense 2003-08-28
Availability unrestricted
Abstract

Environmental stresses arising from temperature and moisture changes, and/or other aggressive fluid ingressions can degrade the mechanical properties of the adhesive, as well as the integrity of an adhesive interface with a substrate. Therefore such disruptions can significantly reduce the lifetime and durability of an adhesive joint.1-4 In this research, the durability of certain epoxy adhesive joints and coatings were characterized using a fracture mechanics approach and also by constant frequency impedance spectroscopy.

The shaft-loaded blister test (SLBT) was utilized to measure the strain energy release rate (G) or adhesive fracture energy of a pressure sensitive adhesive tape. In this study, support for the value of the SLBT fracture mechanics approach was obtained. The SLBT was then used to investigate the effects of relative humidity on a model epoxy bonded to silicon oxide. Lastly, the effects of water and temperature on the adhesion of a commercial filled epoxy bonded to silicon oxide was characterized and interpreted.

A novel impedance sensor for investigating adhesion was developed in a collaborative effort between Virginia Tech and Hewlett-Packard. Utilizing the technique of constant frequency impedance spectroscopy, the distribution and transport of fluids at the interface of adhesive joints was measured. A broad spectrum of adhesives was tested. In addition, the effects of hygroscopic cycling on the durability of adhesive coatings were measured for the commercial filled epoxy using the device. Lastly, recommended modifications of the experimental set-up with the new sensor are proposed to improve the technique.

free literature