Accession Number : ADP006004

Title :   Bearing-Bypass Loading on Bolted Composite Joints,

Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER

Personal Author(s) : Crews, J. H., Jr. ; Naik, R. A.

Report Date : MAR 1988

Pagination or Media Count : 13

Abstract : A combined experimental and analytical study has been conducted to investigate the effects of simultaneous bearing and bypass loading on graphite/epoxy (T300/5208) laminate. Tests were conducted with a test machine that allows the bearing-bypass load ratio to be controlled while a single-fastener coupon is loaded to failure in either tension or compression. Test coupons consisted of 16-ply quasi-isotropic graphite/epoxy laminates with a centrally-located 6.35-mm bolt having a clearance fit. Onset-damage and ultimate strengths were determined for each test case. Next, a finite element stress analysis was conducted for each test case. The computed local stresses were used with appropriate failure criteria to analyze the observed failure modes and strengths. An unexpected interaction of the effect of the bypass and bearing loads was found for the onset of compression-reacted bearing damage. This interaction was caused by a decrease in the bolt-hole contact arc and a corresponding increase in the severity of the bearing loads. The amount of bolt-hole contact had a significant effect on local stresses and, thus, on the calculated damage-onset and ultimate strengths. An offset-compression failure mode was identified for laminate failure under compression bearing-bypass loading. This failure mode appears to be unique to compression bearing-bypass loading and, therefore, cannot be predicted from simple tests. (SDW)

Descriptors :   *BEARINGS, *BOLTED JOINTS, *COMPOSITE MATERIALS, FAILURE, FINITE ELEMENT ANALYSIS, JOINTS, LAMINATES, LOADS(FORCES), MACHINES, STRESS ANALYSIS, STRESSES, SYNCHRONISM, TEST AND EVALUATION, TEST EQUIPMENT.

Subject Categories : Laminates and Composite Materials
      Couplers, Fasteners, and Joints

Distribution Statement : APPROVED FOR PUBLIC RELEASE