The Mechanisms of Elevated Temperature Property Losses in High Performance Structural Epoxy Resin Matrix Materials after Exposures to High Humidity Environments
Abstract
The objective of this research program was the determination of the mechanisms by which epoxy resins utilized in high performance composites and adhesives exhibit losses in their elevated temperature properties as a result of exposure to a humid environment. The study specifically considered an epoxy resin formulation that is characteristic of a variety of composite and adhesive systems. The moisture absorption and diffusion characteristics of this resin system were first investigated as a function of simple humidity environments and simulated real-life environments which included therm spikes. In addition, the effect of absorbed moisture on the resin system's glass transition temperature, T(g), was determined as a function of both simple humidity and real-life exposures. This was followed by a study into the tensile and creep behavior of the epoxy resin as a function of absorbed moisture. A variety of experimental techniques were utilized to accomplish these studies: constant strain rate and dynamic tensile measurements, infrared spectroscopy, heat distortion tests, bomb creep tests, scanning electron microscopy, polarized-light photomicroscopy, and ESCA. The results established that moisture plasticized this particular epoxy resin, causing a lowering of the Tg which in turn affected mechanical response, such as by shifting the relaxation moduli to shorter times. This phenomenon is described and quantified in terms of an existing free volume theory relationship.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1977
- Accession Number
- ADA039754
Entities
People
- Charles Edward Browning
Organizations
- Air Force Research Laboratory