Graphite fiber reinforced composite, polyimide

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. 

Sliney, H.E. and Jacobson, T.P., Graphite-Fiber-Reinforced Polyimide Liners of Various Compositions in Plain Spherical Bearings, Proc. 2nd ASLE Inti. Conf. on Solid Lubrication, Denver, Colorado, (15-18 Aug. 1978) ASLE SP-6, p. 258. 

Graphite Fiber Reinforced TSTR Polyimide Composites (3). 

The flexural strengths (three-point method) of these two unidirectional HMS graphite fiber reinforced TSTR polyimide composites with or without post curing were measured with a universal Instron machine at room temperature and at 316°C. These results are shown in Table II. 

Figure 5. Bunsen burner burning test of graphite fiber reinforced polyimide composites. Key a, TSTR-XL-PI/GrF specimen before test b, TSTR-XL-PI/GrF specimen after test and c, PMR-15-PI/GrF specimen after test.

A large number of studies have been made on a of polymer matrix composites of epoxy, polyimide and other polymers reinforced with carbon and Kevlar fibers [117-123]. The carbon and graphite fibers are characterized by slightly negative (Xi in their axial directions and very large positive aj in their radial directions [122-124]. The unidirectional and bidirectional composites based on them are found to demonstrate highly anisotropic thermal expansion behavior. In unidirectional composites,... 

Kimura [37] selected three kinds of thermosetting resins—furan, diphenylether-formaldehyde and polyimide resins—as matrix precursors to fabricate carbon fiber reinforced carbon composites (C/C composites). After heat treatment at 2000-3000°C, the graphitization process of the matrix was examined by optical microscopy and X-ray diffraction. In the C/C composite derived from a polyimide, the graphite structure was not as well developed as the others. This retarded development is attributed to less internal stress between fibers and matrix as well as to less stretching of the matrix. 

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