scholarly journals Three-dimensional constitutive model for elastic-plastic behaviour of fibre-reinforced composites

2018 ◽  
Vol 139-140 ◽  
pp. 150-162 ◽  
Author(s):  
Simon P.H. Skovsgaard ◽  
Henrik Myhre Jensen
Keyword(s):  
Constitutive Model ◽  
Three Dimensional ◽  
Reinforced Composites ◽  
Elastic Plastic ◽  
Plastic Behaviour ◽  
Fibre Reinforced Composites

scholarly journals A novel rapid method of purely elastic solution correction to estimate multiaxial elastic-plastic behaviour

2019 ◽  
Vol 6 (3) ◽  
pp. 269-283
Author(s):  
Nicolas Antoni
Keyword(s):  
Three Dimensional ◽  
Elastic Solution ◽  
Upper And Lower Bounds ◽  
Efficient Design ◽  
Effective Parameters ◽  
Relative Deviation ◽  
Elastic Plastic ◽  
Plastic Behaviour ◽  
A New Technique ◽  
Good Agreement

Abstract In structural analysis, it is of paramount importance to assess the level of plasticity a structure may experience under monotonic or cyclic loading as this may have a significant impact, particularly in fatigue analysis for singular areas. For efficient design analyses, it is often searched for a compromise in accuracy that consists in correcting a purely elastic analysis, generally simpler and faster to obtain compared to a full non-linear Finite Element (FE) analysis involving elastic-plastic behaviour, to estimate the actual elastic-plastic solution. There exists a great number of correction techniques in the literature among which the most famous and commonly used are Neuber and ESED energy-based methods. Nonetheless, both of them are known to provide respectively upper and lower bounds of the exact solution in most cases, with a relative deviation depending on the level of multiaxiality and on the amount of stress redistribution due to yielding. The new methodology presented in this paper is based on the well-known multiaxial Radial Return Method (RRM) revisited using effective parameters approach. By essence, it is fast and can be applied either to analytical elastic problems or to more complex three-dimensional elastic FE analyses. The accuracy of the proposed method is assessed by direct comparison with results from Neuber and ESED methods on various examples. It is also shown for each of them that this new method is very good agreement with the exact elastic-plastic solution. Highlights A new technique of purely elastic solution correction is presented and evaluated. The proposed method relies on the modification of Return Radial Method (RRM) considering effective parameters in lieu of initial elastic tensor. The obtained equation preserves the simplicity and efficiency of other well-known energy-based methods such as Neuber and ESED. It is shown on several examples that the proposed technique is in very good agreement with the exact or FE elastic-plastic solution, with very low relative deviation.

The effect of microscale residual stress from thermal cooldown on the nanoindentation properties of fibre-reinforced composites

2016 ◽  
Vol 50 (29) ◽  
pp. 4147-4158 ◽  
Author(s):  
M Hardiman ◽  
TJ Vaughan ◽  
CT McCarthy
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fibre Composite ◽  
Three Dimensional ◽  
Interfacial Region ◽  
Indentation Modulus ◽  
Reinforced Composites ◽  
Carbon Fibre Composite ◽  
Residual Stress State ◽  
Fibre Reinforced Composites

A two-step finite element framework is presented that examines the effect of microscale thermal residual stress on the nanoindentation properties of fibre-reinforced composites. Firstly, micromechanical modelling is used to determine the residual stress state following thermal cooldown of a carbon-fibre composite material from cure temperature. A three-dimensional finite element nanoindentation model is then used to characterise the effects of residual stress on material properties determined by nanoindentation theory. The results show that the hardness of the matrix pockets decreases following thermal cooldown due to the existence of equibiaxial tensile residual stresses. The hardness property is also found to decrease for the majority of interfacial region stress states, while the microstructural areas where the effects of the residual stress are nullified are determined. The indentation modulus property is relatively insensitive to the microstructural residual stress, and thus is the recommended indentation property to be determined when carrying out a comparative parametric analysis between microstructural regions. The property changes are shown to be insensitive to any errors associated with contact area estimation using the Oliver and Pharr method.

On the Extraction of Elastic–Plastic Constitutive Properties From Three-Dimensional Deformation Measurements

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
A. J. Gross ◽  
K. Ravi-Chandar
Keyword(s):  
Constitutive Model ◽  
Tensile Test ◽  
Three Dimensional ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Model Parameters ◽  
Material Models ◽  
Elastic Plastic ◽  
Constitutive Properties ◽  
Deformation Measurements

In this article, a coupled experimental and numerical method is utilized for characterizing the elastic–plastic constitutive properties of ductile materials. Three-dimensional digital image correlation (DIC) is used to measure the full field deformation on two mutually orthogonal surfaces of a uniaxial tensile test specimen. The material’s constitutive model, whose parameters are unknown a priori, is determined through an optimization process that compares these experimental measurements with finite element simulations in which the constitutive model is implemented. The optimization procedure utilizes the robust dataset of locally observed deformation measurements from DIC in addition to the standard measurements of boundary load and displacement data. When the difference between the experiment and simulations is reduced sufficiently, a set of parameters is found for the material model that is suitable to large strain levels. This method of material characterization is applied to a tensile specimen fabricated from a sheet of 15-5 PH stainless steel. This method proves to be a powerful tool for calibration of material models. The final parameters produce a simulation that tracks the local experimental displacement field to within a couple percent of error. Simultaneously, the percent error in the simulation for the load carried by the specimen throughout the test is less than 1%. Additionally, half of the parameters for Hill’s yield criterion, describing anisotropy of the normal stresses, are found from a single tensile test. This method will find even greater utility in calibrating more complex material models by greatly reducing the experimental effort required to identify the appropriate model parameters.

Extrusion Freeform Fabrication of Chopped-Fibre Reinforced Composites

1997 ◽  
Vol 9 (4) ◽  
pp. 449-456 ◽  
Author(s):  
Paul Calvert ◽  
Tung Liang Lin ◽  
Hogan Martin
Keyword(s):  
Carbon Fibre ◽  
Epoxy Resin ◽  
Elastic Properties ◽  
Fibre Orientation ◽  
Three Dimensional ◽  
Reinforced Composites ◽  
Freeform Fabrication ◽  
Large Influence ◽  
Fibre Reinforced Composites ◽  
Extrusion Freeform Fabrication

Extrusion freeform fabrication is a process whereby three-dimensional parts are built by writing successive layers of material onto a support. In this case, two types of epoxy resin have been formed into test bars containing varying fractions of chopped carbon fibre of various lengths. It is shown that the fibre orientation follows the writing direction and has a large influence on the directional elastic properties of the composite. Test bars have also been formed containing multiple layers of reinforced and unreinforced resin to demonstrate the flexibility of this method.

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