An Assessment of the Fracture Resistance of Three Chopped-Fiber Reinforced Phenolic Materials.
ARMY MISSILE RESEARCH DEVELOPMENT AND ENGINEERING LAB REDSTONE ARSENAL ALA GROUND EQUIPMENT/MATERIALS DIRECTORATE
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Fracture toughness tests were conducted on three chopped-fiber reinforced phenolic materials. The three materials, supplied by Swedlow, Inc., are designated as FM 4030-190, FM 5821, and MX 2222-67. The standard ASTM method of three-point bending for the testing of metals was used as a guide for the testing program. FM 4030-190 and FM 5821 were also tested at approximate temperatures of -40 F and 140 F. The nonlinearity of the load-crack-opening displacement curves indicated a material toughness too great for the critical stress intensity factor to be determined by the ASTM method. In comparing the failure loads and the crack-opening displacement, the material MX 2222-67 was observed to have the least toughness, failing catastropically when the maximum load was reached. Materials FM 4030-190 and FM 5821 were much tougher, failing in a slow tearing mode. In comparison with MX 2222-67, the failure loads and the crack-opening displacement at failure, respectively, were about 3.6 and 6.4 times as grest for FM 4030-190 and about 3.7 and 4.9 times as great for FM 5821. The failure loads of FM 4030-190 and FM 5821 increased for the cold tests and decreased for the hot tests. The decrease at the higher temperature was not severe. The toughness of FM 5821 varied less with the changes in temperature. Results were also obtained for the strength of the MX 2222-67 material based on bending tests of small beams cut from four liners, aged from 11 to 55 months.
- Laminates and Composite Materials