Static Strength of Film Reinforced Mechanical Joints in Fibrous Composites.
Final technical rept. 8 Aug 69-20 May 71,
NATIONAL RESEARCH CORP CAMBRIDGE MASS
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The joint strengthening effect of plane- isotropic boron film reinforcement added to fibrous laminates was investigated. Uniaxial, bi-axial, and tri-axial graphite fiberepoxy resin composites were fabricated to form a series of double lap bolted joint models. There were tested to measure the joint-strength effectiveness of the plane- isotropic boron film when added locally at 6 and 12 volume percent levels. The results showed that the addition of omni-directional film plies to the highly directional fiber laminae increased the joint strength and stiffness up to 200, the chief contribution of the boron film being high bearing strength and resistance to shear distortion. A novel test method for bolted lap joints was developed in which the bolt head pressure was maintained constant by means of preloaded springs, thus eliminating the ambiquity resulting from an unknown contribution of the bolt clamping friction to the total joint strength. The strength- weight-effectiveness of boron film reinforcement was demonstrated. Author, modified-PL
- Laminates and Composite Materials
- Couplers, Fasteners and Joints