Undergraduate Research on High Temperature Creep Behavior of Polymers

Creep is very slow deformation of materials at cons ta t temperature and under steady stress. It is a diffusion phenomenon accelerated by higher temper atures at stress level below yield strengths. Although the result of creep in all materials are s imilar but physical mechanisms of creep in metals and polymers are very different because of t he difference in the atomic and crystal structures. Specific knowledge of creep deformati on is necessary for design and application of polymer based products at elevated temperatures. A senior design group was assigned a project to design and build a high temperature tester for p olymers. The tester was designed to utilize small standard dog bone specimens under tensile loa d inside a heated chamber. It was equipped with automated temperature control and instrumented for computerized monitoring and logging of both temperature and elongation over time. Succ essful tests on a limited set of industrial polymers demonstrated the functionality of the test er. The results provided good estimates of the creep behavior of the experimental polymers for design purposes that were not easily available in the literature. Two minority and two h nors research students were also engaged to fine tune the hardware, install and test the data a cquisition system, and finally perform a range of creep experiments on the tester. The data on creep rat s and times to failure conform to the hypothesis that these would be affected proportiona ely s stress and temperature are changed. Not only the design and operation of the tester gav e the students high level of creep awareness and knowledge but also the tester and the experimen tal process now provide opportunities for generating experimental creep data for design and r esearch purposes. The design groiup and the research students were all very enthusiastic to be part of such a novel laboratory experience. A few upgrading ideas are being considered for improv ing the functioning, monitoring, and utility of the tester.