DEVELOPMENT OF TEST METHODS FOR GRAPHITE FIBERS

ESTABLISHMENT OF A SET OF COMPREHENSIVE TEST METHODOLOGIES FOR DIRECTLY CHARACTERIZING STRAIN BEHAVIOR IN GRAPHITE FIBERS AND FILAMENTS WITH A NON-CONTACTING LASER EXTENSOMETER IS PROPOSED. THESE METHODS WILL ALLOW RESEARCHERS TO BETTER CALCULATE ELASTIC MODULUS, ELASTIC LIMITS, YIELD POINTS, ULTIMATE STRAIN, AND CONSTRUCT STRESS/STRAIN CURVES FOR INDIVIDUAL GRAPHITE FILAMENTS AND FIBERS BUNDLES. THE PROGRAM WILL DEVELOP LASER EXTENSOMETER TEST METHODS FOR CYCLIC AND MONOTONIC (OBSERVING ELASTIC AND PERHAPS PLASTIC BEHAVIOR) LOADING CONDITIONS, VARIOUS GRAPHITE SPECIMEN GEOMETRIES, AND TESTING WITH AN ENVIRONMENTAL CHAMBER. THE RAPID DEVELOPMENT OF NEW COMPOSITE SYSTEMS UTILIZING GLASS OR GRAPHITE REINFORCING FILAMENTS HAS MADE IT NECESSARY FOR RESEARCHERS TO USE NONCONTACTING, OPTICAL EXTENSOMETRY TECHNIQUES. THE LASER EXTENSOMETER IS A POWERFUL RESEARCH TOOL FOR STUDYING STRAIN BEHAVIOR BUT REQUIRES CAREFUL USE AND AN UNDERSTANDING OF PROVEN TEST METHODOLOGIES. THIS PROPOSED PROJECT WILL DEVELOP, THROUGH EXPERIMENTATION AND ANALYSIS, A SET OF COMPREHENSIVE TEST METHODS FOR SETTING-UP A LEASER EXTENSOMETER, ALIGNMENT TECHNIQUES FOR DARK GRAPHITE FILAMENTS (DIAMETER OF > OR - 0.001"), ON-LINE MEASUREMENT TECHNIQUES, DATA ANALYSIS FOR STRESS/STRAIN CURVES, AND ERROR ANALYSIS.