The effect of isothermal exposure on the transverse properties of a continuous fibre metal-matrix composite

The effect of isothermal exposure at 500° C on the transverse mechanical properties of 30 and 50 vol % continuous boron-fibre reinforced 1100 aluminium composites has been investigated. Experimental results indicate that the fibre-matrix interfacial reaction gives rise to an increase in the fibre-matrix bond strength. Consequently, the fracture mode undergoes a transition from interfacial debonding to fibre splitting with increasing exposure time. The fracture surfaces and fibre-matrix interfaces have been studied by scanning electron microscopy and the observations coincide with the above interpretation of the mechanical test results. Finally, a new theoretical model using Eshelby's theory is developed to analyse the stress-strain behaviour of a continuous fibre reinforced metal matrix composite subjected to transverse tensile loading.On leave from Pioneering R & D Laboratories, Toray Industries, Inc., 2-1, 3-chome, Sonoyama, Otsu, Shiga 520, Japan.     

Void growth in a viscous metal

An investigation is made of void growth in a viscous metal. First, the effective viscosity μ and expansion viscosity κ of a viscous body containing spherical voids is estimated. Then the growth of a typical void embedded in a compressible viscous body with μ and κ is studied. The analytical tool used in this study is a combination of Eshelby's equivalent inclusion method and Mori-Tanaka's back stress analysis. By Mori-Tanaka's back stress analysis the interaction among voids which is enhanced at larger volumn fractions of void can be taken into account in our analysis.     

Response of human epithelial cells to culture surfaces with varied roughnesses prepared by immobilizing dendrimers with/without D-glucose display

To investigate the response of human epithelial cells to substrates with nanoscale modifications, dendrimer-immobilized surfaces were prepared with or without D-glucose displayed as a terminal ligand, giving topographic structures with mean roughnesses (R(a)) of 1.8-11.0 nm. With an increase in the R(a) value up to 4.0 nm, the epithelial cells cultured on naked dendrimer surface without D-glucose display were somewhat stretched in their morphology compared with those on a nonmodified plain surface. However, for the R(a) values higher than 4.0 nm, such cell stretching was inhibited, resulting in the predominant existence of round-shaped cells. The change in cell morphology was appreciable on the surfaces with D-glucose-displayed dendrimers. When the R(a) value increased up to 4.5 nm on these surfaces, in particular, the enhancement of cell stretching was recognized, and fluorescence microscopic observation supported the hypothesis that the glucose-transporter-mediated adhesion of cells to the surface encouraged the development of filopodia and stress fibers, thereby improving focal contact with the surface. Our results suggest that the combination of displaying D-glucose and modulating roughness can promote cytoskeletal formation accompanied by marked cell elongation on culture surfaces.     

Characterization of spatial cell distribution in multilayer sheet of human keratinocytes through a stereoscopic cell imaging system

A novel system was developed to characterize the spatial distribution of human keratinocytes in cultured epithelial sheet, based on stereoscopic observation of nuclei using a confocal laser microscope in combination with image processing. The presented technique allowed understanding of the proliferative and growth-arrested states of cells in multilayered sheet.