A New approach for the numerical assessment of failure of the composite dovetail joint under tensile loading

This paper proposes and tests a new approach to assessing stress-strain states and determining failure regions of thick-walled tapered composite elements. The mesostructure features of composites, such as ply drops and resin pockets, are not explicitly considered in this approach. The constitutive model based on the multiphase finite element approach was extended to describe the three-dimensional stress-strain state. The model consisted of orthotropic linear-elastic and isotropic elastic-plastic sub-elements which simulate the properties of the fibres and matrix, respectively. The assumption of independence of the shear curve from the type of stress state was adopted to describe the nonlinear deformation response in the model. The calibration of the interlaminar nonlinear response of the constitutive model was performed using the test results of V-notched specimens under combined loading. Then, the verified model was used to determine the delamination load of the dovetail specimens. The delamination load of the dovetail specimens was estimated with the Nouthwestern (NU-Daniel) and the Hashin failure criteria. Finite element analysis of the influence of interlaminar strength and taper angle on the failure load of the dovetail specimens was performed. Based on the results obtained, we proposed the method for determining the rational parameters of the dovetail specimen. It was shown that the new approach could be effective for strength assessment and nonlinear behaviour analysis of tapered thick-walled composite structures at interlaminar shear strains up to 6%.