Fiber-matrix mixture

In the in situ consolidation model of Liu [26], the Lee-Springer intimate contact model was modified to account for the effects of shear rate-dependent viscosity of the non-Newtonian matrix resin and included a contact model to estimate the size of the contact area between the roller and the composite. The authors also considered lateral expansion of the composite tow, which can lead to gaps and/or laps between adjacent tows. For constant temperature and loading conditions, their analysis can be integrated exactly to give the expression developed by Wang and Gutowski [27]. In fact, the expression for lateral expansion was used to fit tow compression data to determine the temperature dependent non-Newtonian viscosity and the power law exponent of the fiber-matrix mixture. 

Carbon Composites. In this class of materials, carbon or graphite fibers are embedded in a carbon or graphite matrix. The matrix can be formed by two methods chemical vapor deposition (CVD) and coking. In the case of chemical vapor deposition (see Film deposition techniques) a hydrocarbon gas is introduced into a reaction chamber in which carbon formed from the decomposition of the gas condenses on the surface of carbon fibers. An alternative method is to mold a carbon fiber—resin mixture into shape and coke the resin precursor at high temperatures and then foUow with CVD. In both methods the process has to be repeated until a desired density is obtained. 

Poly(2-hydroxyethyl methylmethacrylate) (PHEMA) has been used as a matrix for the detection of metal ions. 79 A near-IR dye (2,3-naphthalocyanine-tetrasulphonic acid) was immobilized in a polymer matrix which was attached to the reaction phase of two optical fibers. A mixture of the matrix and the dye was prepared by mixing PHEMA and dye in a 60/40 ratio. The optimum ratio of polymer and dye were not fully investigated. The dye/polymer mixture was applied to the tip of the probe in 10-to 15-/iL aliquots forming a thin coating on the probe after solvent evaporation as shown in Figure 7.9. 

Arib et al. [40] investigated the tensile and flexural behaviors of pineapple leaf fiber-reinforced polypropylene composites as a function of volume fraction. The tensile modulus and strength of the composites were found to increase with fiber content in accordance with the rule of mixtures. The flexural modulus gives higher value at 2.7% volume fraction. Scanning electron microscopic studies were carried out to understand the fibers-matrix adhesion and fibers breakage. 

I nformation on the properties of carbon-fiber, metal-matrix composites is still scanty with little or no suitable comparative data available. I n many reports, important variables such as fiber-matrix ratio and fiber orientation are not mentioned. As a rule, the mechanical properties of present composites are still far short of the potential predicted by the rule-of-mixtures. 

Zinc electrodes can also be manufactured by the plastic-bonded method, similar to that of the nickel electrode described above. The zinc oxide dry powder, PTFE binder and other additives are blended with an organic solvent and then the mixture is passed through a calendaring process similar to that in Fig. 31.1. The PTFE fibriUates into a nano-structured three-dimensional fiber matrix. This electrode structure for the calcium zincate electrode is shown in Fig. 31.3 for a freshly prepared electrode. The active materials are locked into the electrode structural matrix which helps to reduce the tendency towards shape change and dendritic growth. 

The impact strength of the composites depends on the nature of the fibers, matrix, fiber-matrix interface, and the test conditions. The experiment results in Table 4.3 may be explained by the interaction observed between fiber and matrix during the mixture process. 

Fig. 2. Ultrafine fibers are produced by spinning bicomponent or biconstituent polymer mixtures, highly stretching such products to ultrafine deniers, and extracting or otherwise removing the undesked matrix carrier to release the desked ultrafine fibers (30). For example, spinning polyester islands in a matrix of polystyrene and then, after stretching, dissolving the polystyrene to leave the polyester fibers cospinning polyester with polyamides, then stretching,...

The density p of the composite material is then related to the density of the fiber and matrix p by the rule of mixtures ... 

Dietary fiber is a mixture of simple and complex polysaccharides and lignin. In intact plant tissue these components are organized into a complex matrix, which is not completely understood. The physical and chemical interactions that sustain this matrix affect its physicochemical properties and probably its physiological effects. Several of the polysaccharides classified as soluble fiber are soluble only after they have been extracted under fairly rigorous conditions. 

---