SEDL / STP / STP636-EB / STP27972S

Improvement of Fatigue Life of Boron/Epoxy Laminates by Heat Treatment Under Load

Sun, CT
Professor, School of Aeronautics and Astronautics, Purdue University, West Lafayette, Ind

Roderick, GL
Aerospace technologist, U.S. Army Air Mobility R&D Laboratory—Langley Directorate, NASA-Langley Research Center, Hampton, Va

Pages: 14    Published: Jan 1977

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Abstract

A heat-treatment procedure was used to produce compressive residual stresses in the matrix of notched [90²/0²]^s and [0²/90²]^s boron/epoxy laminated composites. The residual stress was obtained by using the creep behavior of epoxy under high temperatures. A simple expression for the creep strain was derived from measured creep properties of epoxy. Using this expression a simple creep analysis showed that the residual stress induced by creep of matrix was of the same order of magnitude as the curing stress. Static strength and fatigue tests were conducted on both treated and untreated specimens. The results indicate that the heat treatment has the potential to increase significantly the fatigue life without reducing the static strength of the laminates.