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TITLE	RECENT BIAXIAL TEST RESULTS OF LAMINATED COMPOSITES AND ANALYTICAL MCT PREDICTIONS
AUTHOR(S)	Jeffry S. Welsh, Ph.D. Air Force Research Laboratory/VS 3550 Aberdeen Ave SE, Bldg. 472 Kirtland AFB, NM 87117-5776 Tel: 505.846.7344 Jeffry.Welsh@kirtland.af.mil J. Steven Mayes, Ph.D. Assistant Professor Mechanical Engineering Division Alfred University, Alfred New York, USA Tel: 607.871.2058 mayesjs@alfred.edu
ABSTRACT	As the use of advanced composite materials continues to expand into new technology areas, a troublesome issue arises involving the inability of mainstream designers to accurately predict the initiation and growth of the material damage under multiaxial stress states. This shortcoming has been clearly illustrated in impressive fashion under the recent “World Wide Failure Exercise”. The inability of predict the load response of composite materials in the region of their ultimate load has been primarily attributed to both incomplete development of a general composite failure theory and insufficient multiaxial experimental data for verification. To this end, an ongoing analytical and experimental effort has been pursued by the authors. More specifically, a thickness-tapered cruciform specimen has been developed and shown to be capable of producing acceptable multiaxial results for specific composite laminate architectures. All biaxial tests were performed utilizing a triaxial testing facility located at the Air Force Research Laboratory, Space Vehicles Directorate. This electromechanical test facility was developed specifically to evaluate the biaxial (in-plane) and triaxial (three-dimensional) response of composite materials. This experimental test facility is capable of generating any combination of tensile or compressive stresses in s1:s2:s3 stress space. To date, biaxial tests and numerical predictions have been performed on two laminate stacking sequences, cross-ply and quasi- isotropic, and two material systems, carbon/epoxy and E-glass/vinyl ester. A discussion of the advantages, challenges, and accuracy inherent in the thickness-tapered cruciform specimen’s ability to accurately evaluate the biaxial strength of fiber-reinforced composites will be presented. The results between analytical predictions generated using Multicontinuum Theory (MCT) will be correlated with multiaxial experimental results providing further insight to the capabilities of the current experimental approach.
CONFERENCE	SAMPE 2004 - Long Beach, CA May 16 - 20, 2004
PAGES	15
PRICE	$30.00
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