Carbon matrix materials

Curing primarily refers to the process of solidification of polymer matrix materials. Metal matrix materials are simply heated and cooled around fibers to solidify. Ceramic matrix and carbon matrix materials are either vapor deposited, mixed with fibers in a slurry and hardened, or, in the case of carbon, subjected to repeated liquid infiltration followed by carbonization. Thus, we concentrate here on curing of polymers. 

Those basic matrix selection factors are used as bases for comparing the four principal types of matrix materials, namely polymers, metals, carbons, and ceramics, listed in Table 7-1. Obviously, no single matrix material is best for all selection factors. However, if high temperatures and other extreme environmental conditions are not an issue, polymer-matrix materials are the most suitable constituents, and that is why so many current applications involve polymer matrices. In fact, those applications are the easiest and most straightforward for composite materials. Ceramic-matrix or carbon-matrix materials must be used in high-temperature applications or under severe environmental conditions. Metal-matrix materials are generally more suitable than polymers for moderately high-temperature applications or for modest environmental conditions other than elevated temperature. 

Historically, polymer-matrix composite materials such as boron-epoxy and graphite-epoxy first found favor in applications, followed by metal-matrix materials such as boron-aluminum. Ceramic-matrix and carbon-matrix materials are still under development at this writing, but carbon-matrix materials have been applied in the relatively limited areas of reentry vehicle nosetips, rocket nozzles, and the Space Shuttle since the early 1970s. 

The design of lithium ion batteries has been a great achievement toward overcoming this defect. In these rechargeable batteries, a carbon matrix material is used instead of hthium as the negative electrode which, during charging, takes up hthium ions by cathodic intercalation ... 

Often, the assumption is made that n = 6 i.e., calculations are referred to the graphite ring Cg as a unit in the carbon matrix material.)... 

Murdie, N. Ju, C.P. Don, J. Wright, M.A. Carbon-Carbon Matrix Materials in Carbon-Carbon Materials and Composites, Buchley, J.D., Edie, D.D., Eds. Noyes Publications New Jersey, 1993. 

By solvent extracting the pitch with a solvent system having a solubility parameter of 8.63 a more or less ideal fraction for carbon fiber production is obtained. Extraction with solvent systems of different solubility parameter results in uniform changes in extracted product characteristics which can be tailored to other specific carbon product applications, such as carbon/carbon matrix materials, anodes, etc. 

METHODS OF PROCESSING CARBON-CARBON MATRIX MATERIALS 14.3.1 Introduction... 

CARBON-CARBON COMPOSITE is a carbon fiber reinforced carbon matrix material. The carbon matrix phase is typically formed by solid, liquid or gaseous pyrolysis of an organic precursor material. The matrix is either a GRAPHITIZABLE CARBON or NON-GRAPHITIZABLE CARBON, and the carbonaceous reinforcement is fibrous. The composite may also contain other components in particulate or fibrous forms. 

In addition to differences in the activation energy for the parabolic (diffusion-controlled) portion of the reaction, the extent of the nonparabolic initial portion of the reaction was very dependent, on the nature of the calcium carbonate matrix material. This effect is readily apparent in the data presented in Fig. 4, which is a plot of the weight loss data for samples consisting of 57-// quartz particles in various matrix materials. Although a portion of the curves in the initial few minutes of reaction could be a result of differences in the number of reaction sites, as determined by the number of Si02-CaC03 point contacts, the relative displacement of the curves was found to be far greater than these differences would indicate. 

Fig. 4. Effect of calcium carbonate matrix material on the initial reaction in dry CO2.

An HF acid test was made of the calcium carbonate matrix after mechanically separating it from the reacted quartz particles to determine if the initial portion of the reaction was caused by a rapid silicon transport into the calcium carbonate bulk and subsequent reaction. This analysis showed negligible silicon in the matrix for all the samples. This indicated that differences in the amount of the initial reaction for the various calcium carbonate matrix materials were not due to reaction away from the periphery of the quartz particles. 

A typical product layer on a quartz particle after being reacted with calcium carbonate under dry CO2 conditions at 842°C can be seen in Fig. S(a), The sample consisted of 57-// quartz particles in a matrix of Ge I CaCOa. The weight loss data indicated a 46% reaction. Assuming Ca2Si04 as the reaction product, layer thickness measurements indicated a 58% reaction. The product layer for these conditions was observed to be well defined. The amount of reaction calculated from weight loss data agreed well with values calculated from product layer thicknesses on the basis of 20 different measurements. This agreement was found for all three calcium carbonate matrix materials and confirmed the HF acid test in that reaction was restricted to the quartz particle surfaces. 

Carbon-Carbon Composites. Carbon—carbon composites are simply described as a carbon fiber reinforcement in one or many directions using a carbon or graphite matrix material (see Composite materials). 

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

Naturally, fibers and whiskers are of little use unless they are bonded together to take the form of a structural element that can carry loads. The binder material is usually called a matrix (not to be confused with the mathematical concept of a matrix). The purpose of the matrix is manifold support of the fibers or whiskers, protection of the fibers or whiskers, stress transfer between broken fibers or whiskers, etc. Typically, the matrix is of considerably lower density, stiffness, and strength than the fibers or whiskers. However, the combination of fibers or whiskers and a matrix can have very high strength and stiffness, yet still have low density. Matrix materials can be polymers, metals, ceramics, or carbon. The cost of each matrix escalates in that order as does the temperature resistance. 

The basic questions of The What, The Why, and The How of composite materials and structures have been addressed. Much more could be said about, for example, polymers, metals, ceramics, and carbon used as matrix materials. Also, many more composites manufacturing techniques are available. Moreover, many more examples of effective use of composite materials in structures do exist. However, an introduction to each topic has been provided, and hopefully, those introductions will suffice for the purpose of giving background on composite materials prior to studying their mechanics. 

Shear-stress-shear-strain curves typical of fiber-reinforced epoxy resins are quite nonlinear, but all other stress-strain curves are essentially linear. Hahn and Tsai [6-48] analyzed lamina behavior with this nonlinear deformation behavior. Hahn [6-49] extended the analysis to laminate behavior. Inelastic effects in micromechanics analyses were examined by Adams [6-50]. Jones and Morgan [6-51] developed an approach to treat nonlinearities in all stress-strain curves for a lamina of a metal-matrix or carbon-carbon composite material. Morgan and Jones extended the lamina analysis to laminate deformation analysis [6-52] and then to buckling of laminated plates [6-53]. 

Thermal decomposition of the matrix material offers a simple way of recovering the relatively expensive reinforcing fibres from a fibre-reinforced laminate. The epoxy resin matrix was made to decompose by thermal treatment in air or nitrogen, this treatment allowing the carbon fibres to be recovered without damage. 

As expected, the EDS data set indicates that the polymeric matrix material (the PE-PP blend) is composed only of carbon (hydrogen is not detectable by this method). The particle, however, appears to be composed mainly of aluminum and oxygen along with small amounts of copper. The ratio of aluminum to oxygen is consistent with the chemical formula for aluminum oxide (A1203). The SEM-EDS results are consistent with aluminum oxide and traces of copper as the primary constituents of the particulate contamination. (Al2O3.3H20 is a commonly used fire-retardant additive in polymeric products.)... 

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