Accession Number : ADP006005

Title :   Bolted Joints in Composites Primary Structures,

Corporate Author : ADVISORY GROUP FOR AEROSPACE RESEARCH AND DEVELOPMENT NEUILLY-SUR-SEINE (FRAN CE)

Personal Author(s) : Ruiz, A.

Report Date : MAR 1988

Pagination or Media Count : 8

Abstract : In the design of composite parts in primary structures, it is necessary to use bolted joints because of inspection requirements and the need for partial disassembly, repairability, access to the structure and for manufacturing breaks. The proven methodology for bolted joints in metallic structures cannot directly be applied to bolted joints in composites because of: Material anisotropy, susceptibility to the environment and, specially, due to the brittle behaviour of typical carbon/epoxy joint members up to ultimate failure. In typical highly loaded multirow joints, a tension type failure generally occurs. Peak tangencial stresses at the edge of fastener hole produces fibres break-out. Stress concentration factors governs the failure, as in metal joints under fatigue loads. A methodology for composite bolted joints analysis must be able to size any particular joint design, avoiding the need for detail design tests. The approach under the present work is based on a methodology developed by J. L. Hart-Smith (Douglas. Long Beach) which correlates stress concentration factors in elastic-isotropic materials with those which appear in composites, by means of an empirically determined 'relief' factor. CASA has developed a test plan which includes several hundreds of coupons. Basically, bearing strength allowables and stress concentration factors, are investigated. The plan covers double and single shear specimens, environmental effects (cold-dry and hot-wet), different resin systems and fasteners, and various loading conditions. Provisions for evaluating hole size effect are also made. (SDW)

Descriptors :   *BOLTED JOINTS, *COMPOSITE STRUCTURES, ACCESS, ANISOTROPY, BEARING STRENGTH, BEHAVIOR, BRITTLENESS, COMPOSITE MATERIALS, DISASSEMBLY, ENVIRONMENTAL IMPACT, ENVIRONMENTS, FAILURE, FASTENINGS, FATIGUE(MECHANICS), HOLES(OPENINGS), INSPECTION, JOINTS, LOADS(FORCES), MATERIALS, METAL JOINTS, METALS, PARTS, PLANNING, POLYMERS, REQUIREMENTS, SHEAR PROPERTIES, SIZES(DIMENSIONS), STRESS CONCENTRATION, STRESSES, STRUCTURES, TENSION, TEST AND EVALUATION.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE