Accession Number : AD0470121

Title :   FACTORS CONTROLLING THE STRENGTH OF COMPOSITE BODIES (INTERPHASE FRACTURNG OF COMPOSITE BODIES).

Descriptive Note : Final rept. 17 Feb 64-31 Mar 65,

Corporate Author : MATERIALS RESEARCH LAB INC RICHTON PARK ILL

Personal Author(s) : Mostovoy,S. ; Ripling,E. J.

Report Date : 31 MAR 1965

Pagination or Media Count : 2

Abstract : The fracture toughness of epoxy used in the bulk and adhesive form was measured by a previously developed technique. The uniform double cantilever beam specimen, which was described earlier, was modified to a tapered beam which simplified the experimental procedure and calculations for obtaining toughness measurements. By varying the ratio of hardener to resin and post-cure temperature on a single epoxy system, it was found that the toughness of the epoxy used in either bulk or bond form varied by a factor of approximately five. A particular combination of composition and post-curing temperature generally yielded higher toughness in the bulk than in the bond form. At high post-cure temperatures, however, where the bonds were very tough, their toughness exceeded that of the bulk material. Hence, it does not appear possible to predict joint toughness from bulk toughness measurements. The toughness of joints was found to be a single valued function of tensile modulus. For the bulk material, on the other hand the toughness obtained on the epoxy having a specific modulus depended on the combination of composition and post-cure temperature. Joint toughness for any combination of composition and post-cure temperature depended only on the cracking rate. If the epoxy was the type that caused cracks to jump rapidly, the epoxy was tough and vice versa. For a particular epoxy system, toughness was increased by driving the crack at an increasing rate. (Author)

Descriptors :   (*COMPOSITE MATERIALS, TOUGHNESS), EPOXY RESINS, FRACTURE(MECHANICS), TENSILE PROPERTIES, LAMINATED GLASS, LAMINATED PLASTICS, AGING(MATERIALS), TEST METHODS, ADHESION, BONDED JOINTS

Distribution Statement : APPROVED FOR PUBLIC RELEASE