Modelling manufacturing deformations in corner sections made of composite materials

Abstract

A three-step Finite Element model has been implemented to predict the spring-in of L-shaped parts. The material property development during the cure has been modelled as step changes during transitions between viscous, rubbery and glassy states of the resin. The tool-part interaction is modelled as a sliding interface with a constant sliding shear stress. The effect of various material and geometric variables on the deformation of L-Section parts are investigated by a parameter sensitivity analysis. The spring-in predictions obtained by the Finite Element Method are compared to experimental measurements for unidirectional and cross-ply parts of various thicknesses and radii. Results indicate that although a 2D plane strain model can predict the spring-in measured at the symmetry plane fairly well, it is not sufficient to capture the complex deformation patterns observed.

A thermo-viscoelastic model of process-induced residual stresses in composite structures with considering thermal dependence

“…The distribution of temperature and degree of cure throughout the thickness of part can be neglected due to its thin thickness. Previous studies reported by Ersoy et al found that the tool-part interaction had substantial effects on the residual stresses and distortions in composite structures [5,19,44,45,[56][57][58][59]. The part is assumed to be connected to the mould and no slip is allowed during curing in this investigation.…”

“…the equilibrium stiffness is temperature-dependence. Moreover, some simplified constitutive laws, including the path dependence constitutive model, the two step or three step finite element model and pseudo-viscoelastic model, are developed and validated to be applicable to modelling the residual stresses and distortions of composite structures recently [10,11,[44][45][46].…”

3D finite element model for predicting manufacturing distortions of composite parts

“…A 3D three step model was developed to predict the distortions due to processing using the basic process model previously developed and implemented in ABAQUS by Ersoy et al 13 and Ç ınar et al 14 In this model, the mechanical properties were assumed to be constant within each of the viscous, rubbery and glassy material phases, and the mechanical properties of a single lamina were assumed to be transversely isotropic.…”

“…It is difficult to measure the properties in this step, and there are no data in the literature related to the viscous behaviour. Following the previous parametric study of Ç ınar et al, 14 the shear modulus in this step is assumed to be reduced by a factor of 5. The material in this step is assumed to be linear elastic.…”

“…Arafath et al 7,8 also used the shear layer assumption in a closed-form solution for process-induced stresses and deformations for flat and curved geometries. In some studies, 14,15,24,25 the interfacial shear stress was assumed to obey the Coulomb friction model, 26 where the interfacial shear stress is proportional to the contact pressure with the friction coefficient as the constant of proportionality. The proportionality is maintained until a critical shear stress is reached, after which sliding with constant shear stress is observed.…”