Continuous fiber reinforcement

Particle or discontinuously reinforced MMCs have become important because they are inexpensive compared to continuous fiber-reinforced composites and they have relatively isotropic properties compared to the fiber-reinforced composites. Figures la and b show typical microstmctures of continuous alumina fiber/Mg and siUcon carbide particle/Al composites, respectively. 

In aerospace appHcations, low density coupled with other desirable features, such as tailored thermal expansion and conductivity, high stiffness and strength, etc, ate the main drivers. Performance rather than cost is an important item. Inasmuch as continuous fiber-reinforced MMCs deUver superior performance to particle-reinforced composites, the former are ftequendy used in aerospace appHcations. In nonaerospace appHcations, cost and performance are important, ie, an optimum combination of these items is requited. It is thus understandable that particle-reinforced MMCs are increa singly finding appHcations in nonaerospace appHcations. 

Fig. 14. Failure mechanisms for continuous fiber reinforced ceramic matrices (58).

Domier has developed a production route for continuous fiber-reinforced ceramics based on the impregnation and pyrolysis of Si-polymers. This process is related to the manufacturing of fiber-reinforced plastics and allows the cost-effective production of large and complex CMC-structures. 

Continuous fiber reinforcement, 5 555, 654 performance in ceramic—matrix composites, 5 576-577 Continuous fibers, 11 177... 

James, N.A., Lovett, D.J. and Warwick, C.M. (1991). Mechanical behavior of a continuous fiber reinforced titanium matrix composites. In Proc. ICCMjS. Composites Design, Manufacture and Application (S.W. Tsai and G.S. Springer, eds.), SAMPE Pub., paper 191. 

Jansson. S. and Leekie, F.A. (1992). Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layer. J. Composite Mater. 26, 1474-1486. 

We will see in Section 5.4.2 that the elastic modulus of a unidirectional, continuous-fiber-reinforced composite depends on whether the composite is tested along the direction of fiber orientation (parallel) or normal to the fiber direction (transverse). In fact, the elastic modulus parallel to the fibers, Ei, is given by Eq. (1.62), whereas the transverse modulus, 2, is given by Eq. (1.63). Consider a composite material that consists of 40% (by volume) continuous, uniaxially aligned, glass fibers (Ef =16 GPa) in a polyester matrix (Em = 3 GPa). 

Fiber-Matrix Composites. As shown in Figure 1.75, there are two main classifications of FMCs those with continuous fiber reinforcement and those with discontinuous fiber reinforcement. Continuous-flber-reinforced composites are made from fiber rovings (bundles of twisted filaments) that have been woven into two-dimensional sheets resembling a cloth fabric. These sheets can be cut and formed to a desired shape, or preform, that is then incorporated into a composite matrix, typically a thermosetting resin such as epoxy. Metallic, ceramic, and polymeric fibers of specific compositions can all be produced in continuous fashions, and the properties of the... 

Due to the fact that the mechanical properties of unidirectional, continuous-fiber-reinforced composites are highly anisotropic, maximum effectiveness is often achieved by making laminate composites of multiple layers. This is particularly true of carbon and Kevlar -reinforced polymers, which will be described in Section 5.4.3. 

Assume that the conductivity of a undirectional, continuous fiber-reinforced composite is a summation effect just like elastic modulus and tensile strength that is, an equation analogous to Eq. (5.88) can be used to describe the conductivity in the axial direction, and one analogous to (5.92) can be used for the transverse direction, where the modulus is replaced with the corresponding conductivity of the fiber and matrix phase. Perform the following calculations for an aluminum matrix composite reinforced with 40 vol% continuous, unidirectional AI2O3 fibers. Use average conductivity values from Appendix 8. 

In most materials selection processes, it is virtually impossible to make materials choices independent of the product shape. This includes not only the macroscopic, or bulk, shape of the object such as hammer or pressure relief valve, but also the internal or microscopic shape, such as a honeycomb structure or a continuous-fiber-reinforced composite. Shape is so important because in order to achieve it, the material must be subjected to a specific processing step. In Chapter 7, we saw how even simple objects made from a single-phase metal alloy could be formed by multiple processes such as casting or forging, and how these processing steps can affect the ultimate properties of the material. As illustrated in Figure 8.6, function dictates the choice of... 

Calado, VM.A., Advani, S.G. Processing of Continuous Fiber Reinforced Composites Ch. 2, Hanser... 

Continuous-fiber reinforcement gives plastic products which are not simply quantitatively, but often qualitatively, superior to most present commercial practice. Most plastic processing is limited to conventional melt flow of short-fiber reinforcements, which sacrifices much of the potential benefits of reinforcement. There are a few processes for incorporating continuous fiber reinforcement—filament-winding, pultru-sion, swirl conformation of fibers in polymer... 

In the presentation of the elevated temperature mechanical behavior of ceramic matrix composites, some degree of separation has also been made between fiber-reinforced and whisker- or particulate-reinforced composites. This has been necessary because of the way the field has evolved. The continuous fiber-reinforced composites area in many ways has evolved as a field in its own right, driven by developments in fiber processing technology. 

Following the multiple matrix cracking, the composite can continue to carry the load until fiber failure. The ultimate tensile strengths of several continuous fiber-reinforced ceramic composites versus temperatures are shown in Fig. 

Elevated Temperature Creep Behavior of Continuous Fiber-Reinforced Ceramics... 

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