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Title: Tensile and fatigue strength properties of Kevlar 29 aramid/epoxy unidirectional composites

Static and fatigue tensile strength properties of filament wound undirectional Kevlar 29/epoxy, typical of filament wound material used in flywheel rotors, were studied. Machining techniques were developed to minimize fiber fuzzing on edges. The static modulus, normalized to 70% fiber volume fraction is 8.87 x 10/sup 6/ psi. The major Poisson's ratio is 0.37. The static composite tensile strength, normalized to 70% fiber volume fraction is 200 x 10/sup 3/ psi, corresponding to a fiber stress at failure of 286 x 10/sup 3/ psi, which is good for materials having a very high fiber volume fraction. The S-N curve for R = 0.7 was found to be quite flat. Although the techniques used in this program had previously been employed successfully to study the fatigue behavior of Kevlar 29/epoxy and Kevlar 49/epoxy unidirectional materials, we were unable to overcome the persistent problem of cohesive material failure in the tab regions. The apparent reason for this is the very low interlaminar shear strength of the filament wound material. 16 figures.
Authors:
Publication Date:
OSTI Identifier:
5742716
Report Number(s):
UCRL-15404
ON: DE82006777
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Technical Report
Research Org:
Lawrence Livermore National Lab., CA (USA); General Electric Co., Philadelphia, PA (USA). Valley Forge Space Center
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COMPOSITE MATERIALS; TENSILE PROPERTIES; ARAMIDS; EPOXIDES; FAILURES; FATIGUE; FILAMENTS; POISSON RATIO; MATERIALS; MECHANICAL PROPERTIES; ORGANIC COMPOUNDS; ORGANIC OXYGEN COMPOUNDS; PETROCHEMICALS; PETROLEUM PRODUCTS; PLASTICS; SYNTHETIC MATERIALS 360303* -- Composite Materials-- Mechanical Properties-- (-1987)