SBIR-STTR Award

MMC are viable candidates satellite and spacecraft structures. Their properties and behavior at the low temperatures experienced in low-earth or geocentric orbits or for deep space missions are inadequately known. Netco proposes to obtain these data utilizing specimens of a gr/al unidirectional fiber-reinforced composite. Preliminary non-destructive methods for characterizing panel-to-panel and specimen-to-specimen variability will first be undertaken, and a small number of specimens will be tested at rt 20.0 deg C for longitudinal and transverse strengths, dynamic and static moduli, and strains to failure in tension and compression. Wet chemical analysis will be obtained. Half the remaining specimens will be immersed once or more times in Ln(2 ) and aged to t6. There will be complete characterization and half of them will be statically tested at rt with particular care being taken to determine the elastic limits in longitudinal tension and compression. The remaining t6 specimens will be tested for CTE(l) in the range of rt-Ln(2)-rt, and a small number statically tested in the Ln(2) temperature (-195.8 deg c) .

This effort will determine the cryogenic temperatures at which P100/6061 in the T6 and the annealed condition suffer a decrease in modulus of elasticity. It will also provide data on this material and B(4)C/6o6lt6 after 2000 thermal cycles between -250 deg f and 250 deg f. Also to be evaluated under these conditions will be an adhesively bonded couple simulating the Lockheed truss tubes and end fittings. Damage tolerance as affected by cryogenic temperatures will be determined on B(4)C/6o6lt6, Sic/6o6lt6 and B(4)C/mg by the use of both a mild stress riser (drilled hole) and a severe one (sharp edge crack). Additional work will be performed further defining cryogenic lap joint problems in the bonding of MMC with differences in CTE and investigating the problem of low bond strength of face sheet to matrix of p100 6061 at 250 deg f. Because the truss tubes for Lockheed will be fabricated by pultrusion and diffusion bonding both of these material will be investigated for this problem.