SEDL / STP / STP1189-EB / STP24300S

Translaminate Fracture of Notched Graphite/Epoxy Laminates

Harris, CE
Branch head, Mechanics of Materials Branch, NASA Langley Research Center, Hampton, VA

Morris, DH
Professor and assistant head, Virginia Polytechnic Institute and State University, Blacksburg, VA

Pages: 24    Published: Jan 1993

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Abstract

The strength of three notched graphite/epoxy laminates has been shown experimentally to be a function of laminate thickness. The notched strength of the [0/±45/90]^ns and [0/90]^ns laminates decreased toward asymptotic values with increasing laminate thickness. Conversely, the notched strength of the [0/±45]^ns laminate increased toward an asymptotic value with increasing laminate thickness. For all three laminate types, the notched strength decreased with increasing notch size, regardless of thickness. The fracture of the thick laminates were essentially uniform and self-similar with the notch. The “universal” value of the general toughness parameter, Qc/ε^tuf = 1.5√mm (0.30√in.), developed by Poe successfully predicted the notched strength of the thick laminates. The strength of specimens with surface cuts was predicted using a linear elastic, homogeneous, isotropic fracture mechanics solution.