SEDL / STP / STP1044-EB / STP24593S

The Effect of Processing on Autohesive Strength Development in Thermoplastic Resins and Composites

Howes, JC
Graduate research assistant and associate professor, Virginia Polytechnic Institute and State University, Blacksburg, VA

Loos, AC
Graduate research assistant and associate professor, Virginia Polytechnic Institute and State University, Blacksburg, VA

Hinkley, JA
Chemical engineer, Polymeric Materials Branch, NASA Langley Research Center, Hampton, VA

Pages: 17    Published: Jan 1989

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Abstract

The effects of processing on autohesive bond strength development in polysulfone resin and graphite-polysulfone composites were investigated. Autohesive bond strength development in polysulfone resin was observed by measuring the refracture toughness of precracked compact tension specimens that were healed at a given temperature and contact time. The fractured specimens, when completely healed, achieved the original toughness of the virgin resin. Results of the compact tension (CT) tests, when corrected for nonisothermal effects, compared favorably with diffusion models explaining crack healing and welding of amorphous polymers. Interply strength development in graphite-polysulfone unidirectional composites was measured as a function of healing temperature and contact time using a double cantilever beam (DCB) interlaminar fracture toughness test. The critical strain energy release rate of the refractured composites did not show a strong time or temperature dependence as observed in the neat resin tests. Furthermore, only 80 to 90% of the undamaged fracture energy can be recovered. The fracture mechanisms were determined to be different in the healed DCB specimen from those in the virgin specimen due to resin flow at the crack plane upon healing.