The fiber performance and potential as a reinforcement for fiber composites of a special PAN-based graphite fiber were evaluated by testing the fiber's tensile properties in an epoxy matrix. Representative strand samples were taken from 30 spools (~4 kg) of single-end, 1500-filament fiber to make over 5000 fiber-epoxy strand specimens using the filament-winding process. Characteristics studied were fiber uniformity, strength and modulus distributions at room and liquid nitrogen temperatures, stress-strain behavior, the effect of strain rate on fiber strength, and acoustic emission during tensile loading to failure. The fiber was found to have a 3570-MPa (517 ksi) failure stress, a 1.7 percent failure strain, a 206-GPa (30 x 106 psi) modulus, and a density of 1.77 Mg/m3 at 23 °C (73 °F). Liquid nitrogen temperature and various strain rates had no significant effect on fiber tensile properties.

Large Nd:glass laser disks for disk amplifiers require an edge cladding which absorbs at 1 ?m. This cladding prevents edge reflections from causing parasitic oscillations that would otherwise deplete the gain. We have developed a composite polymer-glass edge cladding that consists of absorbing glass strips bonded to the edges of laser glass disks using an epoxy adhesive. The edge cladding must survive a fluence of approximately 20 J/cm2 in a 0.5-ms pulse. Failure can occur either by decomposition of the polymer or by mechanical failure from thermal stresses which leads to bond delamination. An epoxy has been developed that gives the required damage resistance, refractive index match and processing characteristics, A slight tilt of the disk edges greatly reduces the threat from parasitic oscillations and a glass surface treatment is used to promote bond adhesion. Laser disks fabricated with this new cladding show identical gain performance to disks using conventional fused-glass cladding and have been tested for over 2000 shots (equivalent to about a 4-year lifetime on Nova) without degradation.