Fracture of Thermosetting Polymers: Experiments and Modeling

Abstract

ABSTRACT Fracture of Thermosetting Polymers: Experiments and Modeling. (April 2009) Brad Evin Burgess Department of Aerospace Engineering Texas A&M University Research Advisor: Dr. Amine Benzerga Department of Aerospace Engineering Aircraft are becoming extremely complex in the modern age. Fueled by the advent of new technology, a modern plane’s makeup and structure are changing considerably. Recently the idea to utilize a greater amount of composite materials in creating the next generation of aircraft has surfaced, creating a demand for detailed analysis of these materials. Specifically, the composite fan blade cases on turbofan engines, which protect the greater structure of the aircraft, have come under scrutiny. The cases consist of a carbon fiber resin matrix. The resin can be any one of a number of epoxies, most germane of which is E862. This resin has the effect of strengthening the overall casing structure, but the full nature of its use has yet to be acquired. This information would drastically improve the overall understanding of the uses and implications of E862 in an aerospace environment. During the summer of 2008, extensive tensile testing was conducted on notched E862 specimens at NASA Glenn Research Center in Cleveland, Ohio. It was discovered that the behavior of E862 in tension and fracture was drastically affected by the temperature of the specimen as well as the presence of thermal aging. Specifically, the specimens tested at higher temperatures appeared to yield at lower stress levels, and the aged specimens yielded at higher stress levels. While this testing and analysis exposed a number of interesting material parameters and behaviors, more research must be accomplished before a full understanding can be achieved. The specific fracture mechanics of the resin E862 is a major area of research which must still be considered. This research involves SEM analysis of the fracture surfaces of the test specimens as well as advanced modeling of the fracture using Abacus software and FEM analysis. Once completed, this vital research will serve as a basis through which a more thorough understanding of the fan blade case structure can be gained, and therefore a safer, more structurally sound aircraft will be attainable.