The strength of fiber-reinforced polymers after impact is a concern due to the brittle nature ofcarbon fibers and typical epoxies. At cryogenic temperatures the problem is more severe. Inthis paper the use of Naval Ordnance Laboratory (NOL) ring specimens to study the impactstrength of hybrid composites containing carbon and aramid Zylon~? fibers at cryogenictemperatures is explored. A repeatable and reliable method was established to cut NOL ringspecimens. These rings that represent the cylindrical geometry of a pressure vessel weredamaged by impact and loaded in tension at cryogenic temperatures; where impact damage in theNOL rings is defined as either high (75% of impact breaking energy at cryogenic temperature) orlow (25% of impact breaking energy at cryogenic temperature). Non-impacted rings for eachlayup were also pulled in tension to establish a baseline comparison. A description of the tensiletests conducted on the damaged NOL rings in liquid nitrogen (LN_2) is included. It was foundthat by adding the superior elastic Zylon~? fibers with the carbon fibers laminate brittle failuredue to tension after high and low impact was suppressed or mitigated. From these results it isseen that the Zylon~? drastically improves the impact strength of a carbon fiber based structure ina cryogenic environment.
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