Date of Graduation
Statler College of Engineering and Mineral Resources
Chemical and Biomedical Engineering
Hota V. S. GangaRao
Lack of long term performance data inhibits the widespread use of composites. The long-term response/performance of composite materials and structures exposed under service conditions (load, time, temperature, water, and others) must be established. Creep response under sustained load results in rupture but the time to rupture depends on environmental conditions. Creep rupture tests at higher fractions of ultimate failure load are often used to determine the time necessary to produce failure. Creep data are generated first in terms of deformation/strain versus time up to rupture for each test under a fraction of rupture load at a given temperature. Then the creep data from a large number of tests at various stresses and temperatures are used to develop log-log scale plots of applied stress versus time to failure and the data trend can then be used to extrapolate time to failure (stress rupture, life) under lower fractions of rupture loads for general design purposes. Such an approach is referred to as development of Master curves.;This work, at the Constructed Facilities Center of West Virginia University, focuses on characterization of creep rupture behavior of composite materials using both experimental and theoretical approaches. Composite materials with varying fiber orientations, thickness and manufacturing process were first evaluated under static (tension, compression and bending) loads for their mechanical properties under various environmental conditions. Their flexural creep behavior was also investigated under varying temperatures, moisture contents and loads. Static property data were then used to predict creep curves based on Time Temperature Superposition (TTS) Principle and Miyano's Accelerated Testing Methodology (ATM) approach (Miyano and Nakada, 2008). The predicted creep curves were finally validated through experimental creep data. In addition, Findley Power Law was employed to describe creep strain --time dependence. Our studies demonstrated that the predicted master curves are in good agreement with the experimental data and show great potential to estimate service life of the given composite, thus avoiding cumbersome and time consuming creep tests; and the Findley Power Law is capable of well representing creep strain responses at secondary creep phase for one of the composite materials studied.
Batra, Saurabh, "Creep rupture and life prediction of polymer composites" (2009). Graduate Theses, Dissertations, and Problem Reports. 2035.