Engineering topics
Publications and source records attributed to Marshall, D. B..
This viewgraph presentation provides an overview of research being conducted on the use of C-SiC composite structures for actively cooling rocket nozzles. Potential payoffs and design constraints are discussed. Other topics covered include: testing parameters, material selection, thermal analysis of joined tube structure, pressure containment, H2O2 combustion testing, and cooled re-entry.
Room temperature debonding and sliding of La-Monazite coated fibers is assessed using a composite with a polycrystalline alumina matrix and fibers of several different single crystal (mullite, sapphire) and directionally solidified eutectic (Al2O3/Y3Al5O12 and Al2O3/Y-ZrO2) compositions. These fibers provide a range of residual stresses and interfacial roughnesses. Sliding occurred over a debond crack at the fiber-coating interface when the sliding displacement and surface roughness were relatively small. At large sliding displacements with relatively rough interfaces, the monazite coatings were deformed extensively by fracture, dislocations and occasional twinning, whereas the fibers were undamaged. Dense, fine-grained (10 nm) microstructures suggestive of dynamic recrystallization were also observed in the coatings. Frictional heating during sliding is assessed. The possibility of low temperature recrystallization is discussed in the light of the known resistance of monazite to radiation damage. The ability of La-Monazite to undergo plastic deformation relatively easily at low temperatures may be enabling for its use as a composite interface.
A technique is presented for analyzing high-temperature oxide superconductors using hysteretic magnetic force/distance measurements. Emphasis is placed on developing low weight, highly robust superconducting materials for space applications. Bi-Ca-Sr-Cu superconductors are prepared and characterized by standard techniques. It is found that standard techniques such as XRD, SEM, and TEM are insufficient to completely characterize superconductors. The magnetic properties of the superconductors are studied with the new technique, based on measuring the force between a magnet and the superconductor as a function of their separation.