MULTI FIBRE

Journal of Materials Science Letters 15,No.21, lstNov.l996,p.l908-ll ANALYSIS OF STRESS CONCENTRATIONS IN MULTI-FIBRE MICROCOMPOSITES BY MEANS OF RAMAN SPECTROSCOPY Van Den Heuvel P W J Peijs T Young R J Eindhoven,University of Technology UMIST Manchester,University... 

Preliminary results are presented showing that Raman spectroscopy makes it possible to measure stress concentration factors in fibres adjacent to a fibre break. Use is made of a carbon/epoxy resin multi-fibre microcomposite, in which five different carbon fibres are aligned parallel in a planar array at a predefined interfibre spacing in a dumbbell-shaped tensile bar. 16 refs. 

T. F. Cooney, H. T. Skinner and S. M. Angel, Comparative study of some fibre-optic remote Raman probe designs. 2. Tests of single-fibre, lensed and flat- and bevel-tip multi-fibre probes, Appl. Spectrosc., 1996, 50, 849-860. 

The globalisation of supply chains and the trends to outsourcing and offshore manufacturing in the search for low labour costs have paradoxically exposed businesses to new risks. For example the abolition of the Multi Fibre Agreement which has removed quota restrictions on low labour cost economies, has enabled those countries to increase their penetration of the market with cheaper imports thus increasing competition for UK manufacturers. 

A similar process can also be used to produce multi-fibre optical elements. In this case, glasses with similar thermal but different optical properties, i.e. different refractive index, have to be used for the process. 

Among the several known types of carbon fibres the discussion in this chapter is limited to the electric arc grown multi-walled carbon nanotubes (MWCNTs) as well as single-walled ones (SWCNTs). For MWCNT we restrict the discussion to the idealised coaxial cylinder model. For other models and other shapes we refer to the literature [1-6],... 

Penetration of dimethyl phosphite into the fibre, accompanied by decomposition of salt linkages and elimination of structural water in a multi-step hydration process. New salt linkages are formed between cationic groups in wool keratin and anionic dimethyl phosphite. 

Figure 5. Single-point IR sensor head layouts a transmission probe with fibre coupling b transflectance probe with variable pathlength and single fibre coupling c (diffuse) reflection probe with single illumination fibre and collection fibre bundle d two-reflection ATR probe with fibre-optic coupling e multi-reflection ATR probe (DiComp -type) f ATR fibre...

Another approach, developed in our laboratory, consists of the compartmentalization of the sensing layer25"27. This concept, only applicable for multi-enzyme based sensors, consist in immobilizing the luminescence enzymes and the auxiliary enzymes on different membranes and then in stacking these membranes at the sensing tip of the optical fibre sensor. This configuration results in an enhancement of the sensor response, compared with the case where all the enzymes are co-immobilized on the same membrane. This was due to an hyperconcentration of the common intermediate, i.e. the final product of the auxiliary enzymatic system, which is also the substrate of the luminescence reaction, in the microcompartment existing between the two stacked membranes. 

The fabrication and characterization of a fiber optic pH sensor based on evanescent wave absorption was presented by Lee63. The unclad portion of a multi-mode optical fibre was coated with the sol-gel doped with pH sensitive dye. The sensitivity of the device increased when the multiple sol-gel coatings were used in the sensing region. The dynamic range and the temporal response of the sensor were investigated for two different dyes -bromocresol purple and bromocresol green. 

The wire beads used are produced from a combination of multi-strand copper, zinc or brass coated high-tensile steel wires. The required number of wires are formed into the required shape and then passed through a cross-head extruder to be coated with rubber compound. The coated wire layers are then formed into a coiled ring and the free wire ends secured together. For certain heavy duty applications use is made of either a light weight rubberised fabric or a small fibre filled rubber sheet to cover the joint area. In some cases the bead construction is also partially vulcanised. 

Because of the importance of particle surface charge in chemical interactions of components of the aqueous fibre and filler suspension, paper makers would like to know the charge characteristics of all of the individual components of the aqueous suspension. However, such information is difficult to obtain experimentally, and some kind of average value is normally the best that can be hoped for in a multi-component system. The techniques used to determine furnish charge are usually one of those described below. 

Accufiber, Inc., Model 100 multi-channel optical fibre thermometer system. Publicity data, Accuft-ber, Inc., Beaverton, Oregon (1989). 

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