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Ultrasonic imaging in the C-scan mode was used in conjunction with the amplitude of the reflected signal to measure the temperature dependence of resin flow rate in single layers of woven carbon fabric. The RFI samples were vacuum-bagged and scanned in a water tank at 50°C, 60°C, 70°C, and 80°C. The measured flow rates were plotted versus inverse viscosity to determine the permeability in the thin film, non-saturated system. The permeability values determined in this work were consistent with permeability values reported in the literature. Capillary flow was not observed at the temperatures and times required for pressurized flow to occur. The flow rate at 65°C was predicted from the measured flow rates, and then measured in a 10-layer laminate. The investigation demonstrates that ultrasonic imaging in the C-scan mode in conjunction with the amplitude of the reflected signal is an effective method for measuring resin flow through fabric.

Pull-out and push-out measurements were performed on glass fibres in an epoxy resin to determine the dependence of bond strength on test temperature and on fibre surface treatment. A comparative analysis of the two techniques was carried out to elucidate elementary processes of polymer-fibre debonding and to determine energy values for adhesional bonds. Differences in bond strength values for pull-out and push-out tests were attributed to failure mechanisms that were either interface-controlled or matrix-controlled. Evidence for the different failure mechanisms characteristic of the two test techniques was provided by an estimation of failure parameters, such as the activation energy for debonding. Failure mechanisms also were manifest in AFM images, showing differences in topography and roughness that depended on fibre surface treatment, test geometry, and test temperature.

A transmission electron microscopy study is presented of sub-boundary defect structures in single crystal TiC. Sub-boundaries consisting of organized dislocation arrays and hexagonal networks were observed. The Burgers vectors of dislocations in the sub-boundaries were determined to be 1/2 , and the dislocations were approximately on {111} planes. Dislocation nodes in hexagonal networks provided preferential sites for nucleation of triangular planar defects. These defects were identified as platelet precipitates of TiB 2, although it was difficult to distinguish between precipitates and impurity-stabilized stacking faults during the initial stages of the precipitation. The precipitates were bounded by Shockley partial dislocations and resided on {111} habit planes. Segregation of impurities to sub-boundaries resulted in unusual platelet configurations involving beak-like extensions on intersecting {111} planes. In such cases, the beak-like extensions were bounded by two uncommon partial dislo...

Interfacial bond strength between epoxy resin and glass fibre was studied using the pull-out and push-out techniques. For untreated fibres, these micromechanical tests gave similar values of the local interfacial shear strength and critical energy release rate. In the case of fibres treated by γ-APS, both tests showed considerable increase in the bond strength. However, for the modified fibres, the pull-out test gave greater values of both interfacial parameters than the push-out test, a result attributed to the different modes of interfacial loading. The different loading patterns also cause different failure mechanisms in these two tests.

Whisker-reinforced ceramics show improvements in a variety of mechanical properties, and because of the inherent thermal and chemical stability of ceramics, it is natural to consider issues related to mechanical behavior at high temperatures. Implementation of ceramic materials in high-temperature structural applications is often limited by creep, and recent studies on Al2O3-SiCw have shown that creep resistance of ceramics can be enhanced by whisker reinforcement. These studies demonstrated that creep response is strongly affected by the presence of the reinforcing phase and the properties of the whisker-matrix interface, in addition, oxidation reactions that occurred during creep degraded interface properties, facilitated microstructural damage, and accelerated creep. The objective of the present study was to determine the effects of test ambients on creep damage mechanisms in Al2O3-SiCw composites and to correlate these observations with compressive creep response under different stress-temperature conditions.

Surfaces of commercially grown edge-defined film-fed growth sapphire (EFG α-Al2O3) were studied in the electron microscope using both reflection electron microscopy (REM) and conventional transmission electron microscopy (TEM). The as-grown sapphire surface, ostensibly $${\rm{\{ }}11\bar 20{\rm{\} }}$$ , was characterized by “rooftop” structures which were often locally periodic. These rooftop structures consisted of alternating $${\rm{\{ }}11\bar 20{\rm{\} }}$$ facets and additional facets inclined a few degrees. The crystallography of the surface facets was analyzed using REM imaging of bulk specimens, and trace analysis of back-thinned plan section TEM specimens. Surface roughness was measured by stylus profilometry. and these measurements were compared to the electron microscopy observations. Fine structural features parallel to $$ $$ directions were also observed in both REM and TEM experiments, and these were attributed to surface steps of atomic scales.

Transmission electron microscopy (TEM) and other techniques were employed to investigate the character of high and low angle boundaries and interfaces in several α-SiC-containing multiphase materials. In reaction-bonded SiC, the reaction of Si vapor with excess free C contained in an α-SiC matrix caused epitaxial growth of additional α-SiC and resultant sub-grain boundary formation. Climb-controlled deformation above 1773K caused the formation of additional, unique subboundaries in this material. In sintered α-SiC containing B and C, the occasionally predicted and reported amorphous boundary phase was not discerned in high resolution TEM or Auger analyses. The addition of MgO to an β-SiC whisker-containing Si3N4 composite resulted both in the formation of an amorphous phase and in the epitaxial crystallization of an MgO-containing silicate phase. Finally, ruby or eximer laser annealing of Ni-coated SiC caused the melting of the Ni and the diffusion of SiC into this molten phase. By comparison, the ion mixing of the Ni via the implantation of Si+ through this metal layer resulted in the sequential formation of numerous layers of varying chemistry. The following sections describe the several forms of these interphase regions and their effect on the structural properties of the various materials.

A primary objective of any wear study is to relate the wear and surface damage to corresponding changes in the subsurface microstructure. Transmission electron microscopy (TEM) is well-suited to this task, enabling one to image with good spatial resolution the internal structure beneath a worn surface. This approach is currently being applied along with scanning electron microscopy (SEIM) to the study of dry sliding wear of titanium against itself and other materials. Titanium is of particular interest because it is a metal with hexagonal structure and only nine available slip systems for plastic deformation by dislocation glide. Cubic metals such as iron and copper, on the other hand, have twelve slip systems and have been studied extensively in wear. Although the wear and friction properties of titanium generally are not good, titanium has seen increasing use in components involving mechanical wear because of its good corrosion properties and high specific strength.