Machine for use in monitoring fatigue life for a plurality of elastomeric specimens

An improved machine is described for use in determining the fatigue life for elastomeric specimens. The machine is characterized by a plurality of juxtaposed test stations, specimen support means located at each of the test stations for supporting a plurality of specimens of elastomeric material, and means for subjecting the specimens at each of said stations to sinusoidal strain at a strain rate unique with respect to the strain rate at which the specimens at each of the other stations is subjected to sinusoidal strain

Mineral maturity and crystallinity index are distinct characteristics of bone mineral

The purpose of this study was to test the hypothesis that mineral maturity and crystallinity index are two different characteristics of bone mineral. To this end, Fourier transform infrared microspectroscopy (FTIRM) was used. To test our hypothesis, synthetic apatites and human bone samples were used for the validation of the two parameters using FTIRM. Iliac crest samples from seven human controls and two with skeletal fluorosis were analyzed at the bone structural unit (BSU) level by FTIRM on sections 2–4 lm thick. Mineral maturity and crystallinity index were highly correlated in synthetic apatites but poorly correlated in normal human bone. In skeletal fluorosis, crystallinity index was increased and maturity decreased, supporting the fact of separate measurement of these two parameters. Moreover, results obtained in fluorosis suggested that mineral characteristics can be modified independently of bone remodeling. In conclusion, mineral maturity and crystallinity index are two different parameters measured separately by FTIRM and offering new perspectives to assess bone mineral traits in osteoporosis

Chemical vapour deposition of very thin coatings on carbon fibre bundles

The continuous deposition of thin coatings of refractory materials on carbon fibre rovings is considered as the impregnation of a endless cylinder with slit-like pores in the direction parallel with the cylinder axis. From such a model, the limits of process parameters for the simultaneous coating of all individual monofilaments are derived. In detail a correlation between the deposition parameters and the resulting layer thickness is discussed for a deposition with high and low conversion respectively. 
 The deposition of thin (0.02 to 0.5 $\mu$m) SiC and TiN layers on carbon monofilaments is described in systematic experiments using a steady state laboratory equipment. The effect on the mechanical properties of the reinforcement fibers is shown

THE CHEMICAL VAPOUR IMPREGNATION OF POROUS SOLIDS. MODELLING OF THE CVI-PROCESS

The paper presents a model of the CVD- and CVI- proceses based on the principles for the description of the gas solid reactions on the outer surface of the substrate and the inner surface of the pores. The model parameters mass transfer coefficient and rate constant of the chemical reaction at the surface were determined experimentally. The model for the inpore deposition takes into account that during the CVI- process the geometry of the pores changes and thus no steady state is reached during the process. The precalculation of the CVI- effect using the above model and experimental results are compared for demonstration of the applicability of the mathematical model. Also for porous substrates with a pore size distribution the model describes quantitatively the impregnation effect. The experimental demonstration was performed as SiC- CVI of substrates with micropores between 3 and 15 µm in diameter and as SiC- CVI of SiC- whisker sheets with a diameter distribution ranging from 0.1 µm to 200 µm

PREPARATION OF SIC-WHISKER REINFORCED CVD-SIC

L'article décrit une étude expérimentelle de la préparation des composites SiC renforcés par des whiskers SiC par la déposition de SiC de la phase vapour (CVD) et l'infiltration de la phase vapeur (CVI) utilisant le trichloromethylsilane (H3CSiCl3, MTS) comme précurseur SiC volatile. La procédure expérimentelle est exprimé par la température de déposition, la pression totale, la composition du gaz porteur et par la concentration du MTS dans la phase gazeuse. Les résultats sont discutés par les changes de la masse, de la porosité et de la distribution de la grandeur des pores. Des micrographies électroniques par balayage sont présentées pour la description de la morphologie des couches déposées. Des dates préalables sur les propriétés méchaniques sont présentées comme résistance à la flexure à la température ambiente. Les paramètres utilisables à obtenir des "all-SiC-Composites" renforcés par des whiskers SiC avec une porosité d'environ 25 vol-% sont discutés en détail.The paper describes an experimental study on the preparation of SiC-whisker reinforced SiC-composites by Chemical Vapour Deposition (CVD) and Chemical Vapour Impregnation (CVI) with trichloromethylsilane as volatile SiC-precursor. The experimental procedure is described in terms of deposition temperature, total pressure, carrier gas composition and content of the MTS (H CSiCl)-precursor in the gas phase. The results are discussed in terms of weight gain, change in porosity and pore size distribution. Scanning electron micrographs are presented for the description of the morphology of the deposits. Tentative values on the mechanical properties of selected samples are given as room temperature flexural strength data. The process parameters to achieve whisker reinforced "all SiC-composites" with about 25 vol-% remaining total porosity are described in detail