An efficient numerical approach to evaluate process-induced free-edge stresses in laminated composites

This paper presents an advanced modeling approach to predict process-induced residual stresses at the free-edge of laminated structures. The numerical model is based on the Carrera Unified Formulation, a numerical tool that allows any kinematic model to be considered without an ad hoc implementation. A layer-wise kinematic model has been adopted to detect the through-the-thickness distributions of transversal stresses. The process's evolution of the material properties is obtained by the RAVEN ® software. A cure hardening instantaneously linear elastic (CHILE) constitutive model was adopted. Peeling and transverse shear stress distributions along free-edges were computed and proved to be very high and localized

A refined model for the prediction of process-induced deformations of composite structures

This paper presents an advanced modelling approach for the prediction of residual stresses and process-induced deformations. The numerical model is based on the Carrera Unified Formulation, a numerical tool that allows any kinematic model to be considered without an ad hoc implementation. The evolution of the material properties during the process is obtained by the RAVEN software. A cure hardening instantaneously linear elastic (CHILE) constitutive model was adopted to investigate the magnitude of residual stresses and deformations. The results have been compared with those from the literature. In addition, Different laminations have been investigated and compared

Buckling behaviour of laminated viscoelastic composites under axial loads

This study investigates the buckling response of viscoelastic composite laminates under compression with the objective of better understanding the ply wrinkling behaviour at the early stage of thermoset composite manufacturing. The composite laminate is modelled as a 3-D viscoelastic solid using two different approaches in Abaqus©. As the application of the built-in viscoelastic model of Abaqus© is limited to isotropic materials, a more versatile orthotropic viscoelastic constitutive model based on differential form (DF) of viscoelasticity implemented as a user material subroutine (UMAT) is employed to elucidate the effect of ply anisotropy on the buckling response of uncured/partially cured unidirectional laminates. Numerical results are compared with the experimental data available in the literature to evaluate the accuracy of the proposed approach. Using the numerical model, the influence of various parameters including loading rates, the instantaneous elastic modulus, and in particular the effects of the ply anisotropy on the buckling behaviour of composite laminates are analysed. It has been found that unlike cured composites, the compressive stiffness of uncured prepregs is mainly dominated by the resin modulus rather than the fibre modulus. Additionally, it is shown that the waviness of fibres (fibre-bed effect) which stiffens the prepreg's transverse and shear properties increases its compressive stiffness slightly while the waviness effect on the post buckling stiffness is relatively significant. Hence, conducting compressive tests on uncured and partially cured prepregs as well as partially cured resin films with different thicknesses is suggested to validate the proposed modelling approach more rigorously