Analysis of Composite Double Cantilever Beam Specimen using13; Various Plate Theories

Mathematical formulation for the analysis of symmetric multidirectional double cantilever beam (DCB) specimen using classical plate theory, first and higher order shear13; deformation plate theories under both generalized plane stress and cylindrical bending conditions is developed to determine the mode I interlaminar fracture toughness of symmetric multidirectional composites. In the present formulation, appropriate matching conditions are applied at the crack tip and these matching conditions at the crack tip are derived by enforcing the displacement continuity at the crack tip in conjunction with the variational equation. Variationally derived matching conditions at the crack tip enforce the shear force to be13; discontinuous at the crack tip. Strain energy release rate (SERR) is calculated using compliance approach. Generalized plane stress and cylindrical bending models are applicable and close to each other for unidirectional and cross-ply composite DCB specimens, where as they differ with each other for composite DCB specimens with angle-ply layers. For multidirectional DCB specimens, appropriate compliance/SERR values are obtained from the13; combination of compliance/SERR values of generalized plane stress and cylindrical bending models and appear to be 13; reasonable and encouraging. Performances of first and 13; higher order plate theory models of DCB specimen are close to each other in predicting the SERR. However, higher order plate theory models of DCB specimen are necessary to determine the proper interlaminar normal stress distribution ahead of the crack tip