Quality Assurance Tests of Five Y-12 Kevlar-49 Spools Used to Fabricate Strands and Reliability Specimens for Stress-Rupture Tests,

An important component of the composite reliability program is the assurance of quality of Kevlar 49, 380-denier yarn and epoxy-impregnated yarn. This yarn, which is used in the fabrication of W-82 components from Kevlar 49/epoxy composites, is also formed into test specimens for long-term, stress-rupture studies and reliability studies. The QA work covered in this report encompasses preparation of impregnated-yarn specimens, examination of the yarn itself and individual fibers therefrom, tensile testing of bare and impregnated yarns and heat-degraded yarns. The yarn samples were all drawn from spools of 380-denier Kevlar 49 shipped to LLNL from Y-12. The resin matrix is an amine-hardened epoxy with low viscosity and long pot life, intended for filament winding. The components are Dow epoxy resin (DER) 332 and Jeffamine T-403 triamine hardener. The stoichiometric combining ratio, which we used in our work, is 100 parts by weight resin to 44 parts hardener. Quality-assurance testing not only verifies that the yarns actually meet the manufacturer's specifications, but also provides data on the relationships between fiber characteristics and the lifetime reliability of fabricated items.