Accession Number : ADP006011

Title :   Behaviour of Mechanically Fastened Joints in Advanced Composites,

Corporate Author : NATIONAL AERONAUTICAL ESTABLISHMENT OTTAWA (ONTARIO) STRUCTURES AND MATERIALS SECTION

Personal Author(s) : Poon, C. ; Gould, R.

Report Date : MAR 1988

Pagination or Media Count : 13

Abstract : In this report, experimental results obtained to date from an on-going test program are presented. The purpose of this program is to evaluate the performance of mechanical fastener systems in Narmco IM6/5245C, a high strain/tough resin composite identified as a promising material system for new aircraft designs. Preliminary results obtained from tensile tests on open-hole specimens and double-lap joints were used to characterize the notch strength and the bearing strength as influenced by the effect of design parameters involving geometric ratios, hole size and fastener torque. A constant amplitude tension-compression (R=-1) fatigue test was performed on a double-lap composite joint to assess a simple and effective technique based on hysteresis measurements for monitoring progressive elongation of a fastener hole. It was found that the hysteresis measurement technique underestimates the actual hole elongation by as much as 26% at the end of the fatigue test. This was explained by the observation that graphite particles formed during the fatigue test reduce the clearance between the hole and the pin. Single-shear composite/titanium joints were tested to evaluate three fastener systems designed specifically for composite applications. Four single-shear joints were tested to date to the ultimate tensile strength. It was found that the Huck interference fit lockbolt fastener system provides a single-shear joint strength 30% higher than that provided by the Cherry Maxifoot blind fastener system and 44% higher than that provided by the SPS COMP-TITE blind fastener system respectively. The single-shear specimens tested were strain-gauged for the purpose of measuring the load transfer and secondary bending. (SDW)

Descriptors :   *COMPOSITE MATERIALS, *FASTENINGS, *JOINTS, AMPLITUDE, BEARING STRENGTH, BENDING, COMPRESSION, ELONGATION, FATIGUE TESTS(MECHANICS), GEOMETRY, GRAPHITE, HOLES(OPENINGS), HYSTERESIS, MEASUREMENT, MECHANICAL COMPONENTS, PARTICLES, RATIOS, REPORTS, SECONDARY, SIZES(DIMENSIONS), STRENGTH(GENERAL), TENSILE PROPERTIES, TENSILE STRENGTH, TENSION, TEST AND EVALUATION, TORQUE, TRANSFER.

Subject Categories : Laminates and Composite Materials
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE