Toughening of Graphite-Epoxy Composites by Interlaminar Perforated Mylar (trade name) Films.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER
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Fracture and notch-strength tests of graphite-epoxy composites have shown that unidirectional lay-ups generally exhibit longitudinal cracking before failure, whereas multidirectional lay-ups fail transversely with little longitudinal cracking. A simple qualitative analysis suggested that the higher matrix shear stresses in unidirectional materials cause the longitudinal cracking, and that this cracking is responsible for the higher toughness of unidirectional composites. In a series of comparative tests, the interlaminar strength of multidirectional composites was reduced by placing perforated Mylar films between laminae tests on notched and slotted specimens showed that the inter-laminar films promoted delamination and longitudinal cracking near the notches and that, as a result, toughness, notch strength, and impact strength were substantially increased. MM
- Laminates and Composite Materials