Separation of crack extension modes in composite delamination problems
- Carnegie Mellon Univ., Pittsburgh, PA (United States)
In order to predict composite delamination resistance, an applied stress intensity factor, K, or energy release rate, G, must be compared to a mode-dependent critical value of K or G from experiment. In the interfacial fracture analysis of most composite applications and some tests, the mode of crack extension is not uniquely defined. It is instead a function of distance from the crack tip due to the near-tip oscillatory singularity. The virtual crack closure technique (VCCT) is a method used to extract mode I and mode II energy release rate components from numerical (typically finite element) models. Crack extension modes extracted from oscillatory analyses using the VCCT are a function of the virtual crack extension length, {Delta}. In this work, a modified method is presented for using the VCCT to extract crack extension modes for the case of an interface crack between two in-plane orthotropic materials. The method does not attempt to alter the analysis to eliminate its oscillatory behavior (e.g. by changing material properties or by embedding the crack in a homogeneous interlayer). Instead, the argument is made that the oscillatory behavior is non-physical and that if its effects were separated from VCCT quantities, then consistent, {Delta}-independent modes of crack extension could be defined. Knowledge of near-tip fields is used to determine the explicit {Delta} dependence of VCCT parameters. Energy release rates are then defined with the oscillatory {Delta} dependence factored out. This modified VCCT method is applied to results from finite element analyses, showing that {Delta}-independent modes of crack extension result. The modified VCCT approach shows potential as a consistent method of extracting crack extension modes. The {Delta}-independent modes extracted using the modified approach can also serve as guides to test the convergence of finite element solutions.
- OSTI ID:
- 175168
- Report Number(s):
- CONF-950686-; TRN: 95:006111-0081
- Resource Relation:
- Conference: Joint applied mechanics and materials summer meeting, Los Angeles, CA (United States), 28-30 Jun 1995; Other Information: PBD: 1995; Related Information: Is Part Of AMD - MD `95: Summer conference; PB: 520 p.
- Country of Publication:
- United States
- Language:
- English
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