Effects of Mode Ratio, Ply Orientation and Precracking on the Delamination Toughness of a Laminated Composite
- 1 February 1996
- journal article
- research article
- Published by SAGE Publications in Journal of Reinforced Plastics and Composites
- Vol. 15 (2), 141-173
- https://doi.org/10.1177/073168449601500202
Abstract
Results are presented from an investigation of the effects of mode ratio, interfacial ply orientation and precracking on the delamination toughness of a graphite/ epoxy composite. Delamination toughness tests were performed on specimens that exhibited growth at 00/00, 15°/15°, 15°/- 150, 30°/30° and 30°/-30° interfaces. Three mode ratios were considered. The double cantilever beam test was utilized for pure mode I, the end-notched flexure test was used for pure mode II, and the symmetrically delaminated single leg bending test was used for a mixed-mode condition, G,,IG, equal to approximately 0.4. All five interfaces were tested in both precracked and non-precracked conditions at each mode ratio. Also, for the 30°/30° and 30°/- 30° interfaces, two different stacking sequences were used to assess the effect of remote ply orientation on the perceived mode I and mode II toughness. For any mode ratio and interface angle, it was found that precracked toughness values were always lower than the corresponding nonprecracked result. No other consistent trends were observed in all of the data. For the mode I tests, the 30/30 interface exhibited the lowest toughness, for the mixed-mode tests, the 0/0 interface produced a minimum toughness, and for mode II no significant effect of interface angle on toughness was observed. These results are interpreted with the aid of recent three dimensional finite element analyses for energy release rate distributions along the delamination front for the different stacking sequences and test geometries. The accuracy of various data reduction techniques are also evaluated, and suggestions are made for future testing.Keywords
This publication has 28 references indexed in Scilit:
- Micromechanisms of Fracture in Toughened Graphite-Epoxy LaminatesPublished by ASTM International ,2008
- Influence of the Resin on Interlaminar Mixed-Mode FracturePublished by ASTM International ,2008
- Mode II fracture of +θ/-θ angled laminate interfacesComposites Science and Technology, 1993
- Stress intensity factors and energy release rates of delaminations in composite laminatesEngineering Fracture Mechanics, 1992
- Mixed-mode bending method for delamination testingAIAA Journal, 1990
- On the Use of Laminated Beams for the Determination of Pure and Mixed-Mode Fracture Properties of Structural AdhesivesThe Journal of Adhesion, 1989
- Interlaminar Shear Fracture Toughness and Fatigue Thresholds for Composite MaterialsPublished by ASTM International ,1989
- On strain energy release rates for interfacial cracks in bi-material mediaEngineering Fracture Mechanics, 1987
- On the Analysis and Design of the End Notched Flexure (ENF) Specimen for Mode II TestingJournal of Composite Materials, 1986
- Moisture and Temperature Effects on the Mixed-Mode Delamination Fracture of Unidirectional Graphite/EpoxyPublished by ASTM International ,1985