Aluminum polymer-matrix composites

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. 

Polymer matrix composites (PMCs), or fiber-reinforced plastics (FRPs). provide a wide range of properties and behavior. Materials with discontinuous fibers are slightly stiffer than conventional unreinforced plastics, whereas the fully aligned continuous fiber systems can record exceptionally high specific properties (property divided by density), exeeeding those of competing materials such as steel and aluminum. There are a virtually infinite number of materials, and material formats that can be combined to form a composite material, as shown in Table 1. 

The slice compression test has been applied to polymer-matrix composites even though it was developed to probe the interface in ceramic matrix composites [16]. A thin slice sample of unidirectional composite is produced with the cut surface perpendicular to the fiber axis. The surfaces are cut and polished to be parallel to each other and perpendicular to the fibers. The thin slice is loaded in compression in the fiber axis direction with two plates. One of the plates is made of a very hard material such as silicon nitride and the other of a soft material, e.g. pure aluminum which can deform as the fibers are compressed into it. The thickness of the slice must be controlled to allow the fibers to debond without failing in compression as well as allowing them to slide inside through the matrix. The depth of the fiber indentation into the plate can be related to the interfacial shear strength [17]. 

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Often there is a borrowing of terms between metal-intense materials science and polymer-intense materials science where there is actually little relationship between the two. This is not the case with metal-matrix composites (MMCs). Although the materials are often different, there are a number of similarities. For polymer-intense composites, the matrix materials are organic polymers. For MMCs, the matrix materials are typically a metal or less likely an alloy. Popular metals include aluminum, copper, copper-alloys, magnesium, titanium, and superalloys. ... 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

In addition, the surface should be free of contaminating particles and occlusions that would interfere with the information retrieval process. A typical ablative-mode optical disk has the structure shown in Figme 16.14. The substrate is an optically transparent material such as polycarbonate, PMMA, polyfethylene terephthalate), or polyfvinyl chloride) topped by a subbing layer to provide an optically smooth surface for the recording layer. A metal reflector (typically aluminum) is then incorporated next to a transparent dielectric medium such as poly(a-methyl styrene) and, finally, the absorbing layer where the information pits are created is added. The latter can be a metal-polymer composite (silver particles in a gel) or a dye molecule dispersed in a polymer matrix such as squaryllium dyes, which act as infrared absorbers for GaAs lasers, typically... 

Both oxide and non-oxide matrices have been used with SiC reinforcements. Examples include alumina matrix composites fabricated by oxidation of an aluminum melt (DIMOX process) (Newkirk et al., 1986), glass-ceramic matrix composites fabricated by hot pressing (Prewo and Brennan, 1980), SiC matrix composites made by CVI (Stinton et al., 1986), SiC or SiC/Si3N4 matrix composites made by polymer pyrolysis, and SiC-Si matrix composites produced by silicon melt infiltration (Luthra et al., 1993). 

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