High Performance Synthetic Fibers for Composites (1992) / Chapter Skim
Currently Skimming:
2 High-Performance Fiber Materials: Applications, Needs, and Opportunities
2 High-Performance Fiber Materials: Applications, Needs, and Opportunities
Pages 21-48
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 21... ...
their function is mainly to exploit some other ~hvsical only mechanical strength HIGH- PERFORMANCE FIBERS FOR POLYMERIC -MATRIX COMPOSITES In the United States, reinforced plastics represent a very large market of approximately 2.3 billion pounds/year, valued at about $2.5 billion. A very important high value-added, but relatively low-volume, sector of the reinforced plastics market is the advanced composites market.
|
From page 22... ...
TABLE 2.1. Advantages of PMCs Good specific stiffness and strength Low density Ease of fabrication Relatively low raw materials cost Potential for lower cost fabrication methods Corrosion resistance Fatigue resistance Low coefficient of thermal expansion Creep and creep fracture resistance Excellent in-service experience Property "tailorability" to application requirements | Major Current Fibers Properties; Demand PMCs are made by combining reinforcing fibers containing high strength and stiffness properties with polymeric matrices to produce tailored materials with combined performance not possible with either constituent alone.
|
From page 23... ...
industrial market segment has experienced gradually increasing growth rates, and it is now the second largest of the three major market segments. The industrial market uses chopped carbon fibers primarily for electromagnetic interference/radio frequency (EMI/RFI)
|
From page 24... ...
24 ma_ mu_ Em_ ~ · ~ ~ ~ ~ ~ ~)
|
From page 25... ...
9 8 in :, o o In A: o ._ 7 4 1 o 2 ~ ~ ~ Commercia/ Military 1976 1 988 1 989 1 990 Year FIGURE 2.2 U.S. Carbon Fiber Consumption Aerospace Market Industrial Sources; Industry Structure; Market Situation The advanced composites industry (particularly, the PMCs component of that industry)
|
From page 26... ...
During the past several years, PAN-based carbon fiber capacity has grown rapidly as companies expanded their capacity to establish market position and meet the growing demand for carbon fibers. For example, in 1980 the total free world capacity2 was just over 1400 metric tons (3 million pounds)
|
From page 27... ...
Future Appl ication Chal l enges The range of future applications for PMCs has the potential to be very large and to encompass a multitude of end-use sectors; some of these end uses, such as military applications will be driven primarily by performance, and the others, such as automotive and general industrial, will be driven primarily by cost e In order for the PMC sector to increase its market share in its current applications and to grow into new applications, it needs to overcome some key hurdles product performance, fabrication, and economic issues. Fiber developments can play an important role in all of these issues.
|
From page 28... ...
Examples of the broad range of applications would include robotics, ropes and cables, heat exchangers, bridge decking, and reinforced concrete. The key to increased consumption in these diverse end uses is reduced raw material costs and improved fabrication technology; with current raw material costs (fibers are a key component of the cost)
|
From page 29... ...
As in the case of other composites discussed in this report, the family of metal-matrix composites is made up of many varieties of materials, which can be categorized based on their matrix composition, fabrication process, or reinforcement type. The generic listing in Table 2.2 TABLE 2.2 Advantage of PMCs Matrix Reinforcement (alloy class)
|
From page 30... ...
Similarly, the mismatch in thermal expansion between fiber and matrix can ruin composite performance on thermal cycling. Finally, the composites may differ in corrosion resistance from the parent matrix because of the composite microstructure and the difference in fiber -matrix electrochemical potential.
|
From page 31... ...
, and Alcan Aluminum of Canada purchased the Dural composites activity and has invested heavily in its expansion. For aerospace-grade MMCs, the production applications, such as the Space Shuttle fuselage struts or satellite members, have occurred within the U.S.
|
From page 32... ...
An exciting future application of metal-matrix composites will be on airbreathing hypersonic vehicles. The national goal of demonstrating a spacecapable aircraft cannot be met with traditional manufacturing processes, materials, and structural concepts.
|
From page 33... ...
These composites constitute a subset of the more traditional MMC systems in that the matrices are ordered structures whose mechanical properties may include limited ductility over certain temperature ranges. The advantages of these systems, however, relate to their low density and high potential for use at elevated temperatures.
|
From page 34... ...
Recommendation: Fibers compatible with low-cost metal-casting processes should be developed. HIGH PERFORMANCE FIBERS FOR CERAMIC MATRIX COMPOSITES Major Current Fibers and Their Properties The addition of fibers and whiskers to ceramic matrices can result in structural composite materials that retain the important advantages of ceramics (i.e., high-temperature resistance, environmental stability, and low density)
|
From page 35... ...
Special mention should be made of the successful flight demonstration by the French company Societe Europeene de Propulsion (SEP) of its chemical vapor infiltration (CVI)
|
From page 36... ...
It is important to note that duPont in the United States has been licensed to use the SEP technology for making SiC-matrix composites by C~I and has made a major investment in establishing a domestic production capability. This is an important example of bringing a non-U.S.-based technology, superior to any in the United States, into this country for application.
|
From page 37... ...
In this case there are two important areas of interest. First, space satellite structures and reflectors must remain very dimensionally stable over the orbital temperature range, they must be resistant to attack by atomic oxygen, and they must be highly damage tolerant.
|
From page 38... ...
6 The potential use of CMCs at very high temperatures can be illustrated by comparing available tensile strength data of several composites with the strength of currently used superalloys (see Figure 2.5~. The comparison does not include the effects of environment since the composites were tested in inert atmosphere.
|
From page 39... ...
The use of carbon fibers provides the highest level of performance owing to carbon fiber's unique low density, high strength, and retention of strength to the highest possible temperature.
|
From page 40... ...
Greenleaf Advanced Composite Materials Oak Ridge National Laboratories GTE Norton Textron Kaiser Aerotech General Atomics Babcock & Wilcox Pratt & Whitney Lan~ude General Electric Although the Nicalon~ fiber tensile strength is expected to decrease significantly at about 1300°C, it is notable that composite strength is maintained even to this temperature. The strength and stability properties of newer versions of Nicalon@8 as well as these of new fibers such as Tyranno9 indicate the potential to increase maximum-use temperatures in the future.
|
From page 41... ...
. For continuously reinforced C-C composites, it is the mechanical properties of the carbon-graphite fibers that dominate the C-C composite properties, and it is the high-temperature capability of the carbon matrix that allows one to take advantage of the fiber properties at elevated temperatures, where most metal matrices have melted or polymer matrices have decomposed or melted.
|
From page 42... ...
The use of C-C composites in hypersonic vehicles will continue, but more benefits can be gained through incorporation of the newly developed, high thermal conductivity, pitch-based carbon fibers. Hypersonic vehicles will need C-C composite leading edge and skin materials to withstand the extreme aerothermal heating of the atmosphere.
|
From page 43... ...
The technical issues involved are discussed further in Chapter 4. HIGH PERFORMANCE FIBERS FOR NONSTRUCTURAL APPLICATIONS As pointed out earlier, composites especially advanced composites are used primarily in structural and semis tructural applications for which the dominant considerations are mechanical properties, such as stiffness, static strength, and resistance to fatigue, creep, and creep rupture.
|
From page 44... ...
The low density of carbon fibers makes them attractive candidates for electrical conductors in applications for which weight is critical. Aircraft and spacecraft are obvious examples.
|
From page 45... ...
Key requirements, in addition to low CTE, are high thermal conductivity and low density. There are no monolithic metals possessing all three characteristics.
|
From page 46... ...
Chemical Properties: Corrosion Resistance Relatively recent work on fiber-reinforced silicon carbide ceramics has shown promise for heat exchangers, furnace tubes, regenerators, nozzles, and other components that may be required to resist thermal shock and corrosive gases at high temperatures for extended periods of time. The ceramic composite type most frequently cited in recent presentations and publications is that prepared by the application of silicon carbide by chemical vapor deposition and chemical vapor infiltration on graphite, carbon, oxide, and silicon carbide textiles.
|
From page 47... ...
Cole, and F Huffman, ''CVD Silicon Carbide Components," Ceram.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.