SURFACE TREATMENTS FOR FIBROUS CARBON REINFORCEMENTS.
Technical rept. May 66-Feb 67,
AVCO MISSILES SPACE AND ELECTRONICS GROUP LOWELL MA AVCO SPACE SYSTEMS DIV
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The use of carbon and graphite fibers as reinforcement in plastics composites may be limited by poor resin-to-fiber bonding that can result in low composite interlaminar shear strength. Treatments have been developed for WYB 85 12 and Thornel 25 graphite fibers that activated the fiber surface and increased the shear strength of epoxy composites. The best treatment was a combination of chemical oxidation with nitric acid, followed by a polymeric coating. The chemical functionality of the fiber surface appeared to have a stronger effect on composite shear strength than did fiber surface area. Ablative composites containing carbon fibers may suffer because carbon is readily oxidized, and, for certain applications, oxidation is a major mechanism of ablation. Fiber treatments and coatings of metals, antioxidants and silica have been applied to carbon fibers in effort to increase their oxidation resistance. Phenolic composites tested in the Model 500 air arc operated under low to medium heating conditions indicated that only silica coatings increased ablative performance, but only at the lower heating conditions where chemical reaction rate is an important ablative mechanism. Author
- Laminates and Composite Materials