ISSN: 0884-6804
Page Count: 12

Failure Criterion for Thick Multifastener Graphite-Epoxy Composite Joints
Prasad, C
Research engineer, Analytical Services and Materials, Inc., VA

Cohen, D
Alliant Technosystems, Inc., UT

Shuart, MJ
Assistant chief, NASA Langley Research Center, VA

Hyer, MW
Professors, Virginia Polytechnic Institute and State University, VA

Griffin, OH
Professors, Virginia Polytechnic Institute and State University, VA

Yalamanchili, SR
Senior project engineer, General Motors Truck Engineering, MI

Abstract

A method for accurately predicting the strength of multifastener, thick composite joints is discussed. The method is based on the average stress criterion applied around the hole circumference. Basic laminate strength data are obtained from single-fastener and reduced-section notched specimens. Using ABAQUS finite element analyses (FEA), the stress-field distribution around the fastener-loaded hole in both the single-fastener and multifastener joints is determined. The single-fastener test data in conjunction with this FEA and the average stress criterion are then used to predict the multifastener joint strength. Multifastener joint strength of three different laminate layups is predicted to within 1% accuracy. However, the results show that the average stress criterion cannot accurately predict the location of failure initiation. In the current investigation, the maximum strain criterion is used to locate possible sites of failure initiation. When this information is used in conjunction with the average stress criterion, the predicted multifastener joint strength based on single-fastener net-tension data is reasonably accurate.

Keywords:
composite average stress criterion, multifastener joints, single-fastener joints, material strength, maximum strain criterion

Paper ID: CTR10489J
DOI: 10.1520/CTR10489J
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