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Papers by imad aldin khattab
Acting Principles of Nano-Scaled Matrix Additives for Composite Structures
This chapter presents the adaptation of the Transformation Field Analysis (TFA) proposed by Dvora... more This chapter presents the adaptation of the Transformation Field Analysis (TFA) proposed by Dvorak et al. for predicting the properties of a representative volume of inelastic heterogeneous materials consisting of polymers and nanoparticles. The TFA method is implemented at the nanoscale as a user routine integrated into Representative Volume Elements (RVE) micro scale model, where the homogenously modelled modified matrix is reinforced by a certain volume fraction of aligned fibres. This yields to save computational resources and time compared to todays established methods with comparable accuracy. Finally, a single nano level application based TFA approach and numerical multi-scale (nano/TFA-micro/FEA) application are implemented to verify the behaviour of elastic-plastic epoxy nanocomposite consisting of agglomerated fillers in nano-scale and reinforced by aligned fibres in micro-scale under different external loads. A multiscale approach based TFA micro scale and TFA nano scale is presented and evaluated.
In this paper, we will present analytical models which enable the characterisation of defects in ... more In this paper, we will present analytical models which enable the characterisation of defects in composite materials. First, a study is introduced to determine the reduction of the material stiffness with analytical models. An analytical model based on the Eshelby theory and a three-dimensional laminate theory has been developed to predict the influence of voids on the material properties of a multi-layered fiber composites. Moreover, an efficient analytical approach is presented to account for the influence of fiber waviness on material stiffnesses of multi-layered fiber composites. The fiber waviness is approximated by periodic functions. Effective material stiffnesses are obtained by inserting the functions into transformation equations and integrating over wavelength and height of the laminate. The results of the analytic studies as a basis for future work will be presented.
Due to defects during the manufacture of ber-reinforced composite materials, nite element analyse... more Due to defects during the manufacture of ber-reinforced composite materials, nite element analyses are performed to investigate the material behaviors. Hashin criteria are emphasized for damage initiation in this thesis since it rst presents a dierent way of approaching the generation of composites failure criteria, in which dierent failure modes are considered. By using build-in Hashin criterion function in the FEM program Abaqus two-dimentional stress analysis can be carried out. It is here assumed that the matrix and ber materials are linearly elastic, isotropic, and homogenous. Due to the ber orientation the reinforced material is anisotropic. This thesis starts from dierent analytical models of a ber-reinforced lamina with initial ber misalignment and its modeling in Abaqus/CAE. Then, the fundamental knowledge of Hashin criterion is introduced and nite element analyses for elastic stinesses and strengths of a carbon-epoxy composite system are performed. Finally, the Hashin crit...
Fiber composite materials provide low material weights in combination with high material stiffnes... more Fiber composite materials provide low material weights in combination with high material stiffness and strength. The fiber stiffness and strength characterize mainly the behavior of unidirectional composites plies. Critical phenomena for composite structures are defects caused by the manufacturing and processing technologies. One such phenomenon which is often detected is fiber misalignment. The paper presents an appropriate 3D finite element model for the analysis of the effects of in-plane and out-of-plane graded fiber waviness on the stiffness and strength values of a laminate which consists of unidirectional plies under shear and tensile loading conditions. The classical laminate theory (CLT) is utilized as analytical model to predict the unidirectional fiber stiffness as a function of in-plane and out-of-plane fibers waviness. Furthermore the undula-tions of fiber are represented by Fourier series. The 3D linear Hashin failure criterion implemented in ABAQUS is functioned by me...
CEAS Aeronautical Journal, 2013
Chemie Ingenieur Technik, 2010
CEAS Aeronautical Journal, 2013
Acting Principles of Nano-Scaled Matrix Additives for Composite Structures
This chapter presents the adaptation of the Transformation Field Analysis (TFA) proposed by Dvora... more This chapter presents the adaptation of the Transformation Field Analysis (TFA) proposed by Dvorak et al. for predicting the properties of a representative volume of inelastic heterogeneous materials consisting of polymers and nanoparticles. The TFA method is implemented at the nanoscale as a user routine integrated into Representative Volume Elements (RVE) micro scale model, where the homogenously modelled modified matrix is reinforced by a certain volume fraction of aligned fibres. This yields to save computational resources and time compared to todays established methods with comparable accuracy. Finally, a single nano level application based TFA approach and numerical multi-scale (nano/TFA-micro/FEA) application are implemented to verify the behaviour of elastic-plastic epoxy nanocomposite consisting of agglomerated fillers in nano-scale and reinforced by aligned fibres in micro-scale under different external loads. A multiscale approach based TFA micro scale and TFA nano scale is presented and evaluated.
In this paper, we will present analytical models which enable the characterisation of defects in ... more In this paper, we will present analytical models which enable the characterisation of defects in composite materials. First, a study is introduced to determine the reduction of the material stiffness with analytical models. An analytical model based on the Eshelby theory and a three-dimensional laminate theory has been developed to predict the influence of voids on the material properties of a multi-layered fiber composites. Moreover, an efficient analytical approach is presented to account for the influence of fiber waviness on material stiffnesses of multi-layered fiber composites. The fiber waviness is approximated by periodic functions. Effective material stiffnesses are obtained by inserting the functions into transformation equations and integrating over wavelength and height of the laminate. The results of the analytic studies as a basis for future work will be presented.
Due to defects during the manufacture of ber-reinforced composite materials, nite element analyse... more Due to defects during the manufacture of ber-reinforced composite materials, nite element analyses are performed to investigate the material behaviors. Hashin criteria are emphasized for damage initiation in this thesis since it rst presents a dierent way of approaching the generation of composites failure criteria, in which dierent failure modes are considered. By using build-in Hashin criterion function in the FEM program Abaqus two-dimentional stress analysis can be carried out. It is here assumed that the matrix and ber materials are linearly elastic, isotropic, and homogenous. Due to the ber orientation the reinforced material is anisotropic. This thesis starts from dierent analytical models of a ber-reinforced lamina with initial ber misalignment and its modeling in Abaqus/CAE. Then, the fundamental knowledge of Hashin criterion is introduced and nite element analyses for elastic stinesses and strengths of a carbon-epoxy composite system are performed. Finally, the Hashin crit...
Fiber composite materials provide low material weights in combination with high material stiffnes... more Fiber composite materials provide low material weights in combination with high material stiffness and strength. The fiber stiffness and strength characterize mainly the behavior of unidirectional composites plies. Critical phenomena for composite structures are defects caused by the manufacturing and processing technologies. One such phenomenon which is often detected is fiber misalignment. The paper presents an appropriate 3D finite element model for the analysis of the effects of in-plane and out-of-plane graded fiber waviness on the stiffness and strength values of a laminate which consists of unidirectional plies under shear and tensile loading conditions. The classical laminate theory (CLT) is utilized as analytical model to predict the unidirectional fiber stiffness as a function of in-plane and out-of-plane fibers waviness. Furthermore the undula-tions of fiber are represented by Fourier series. The 3D linear Hashin failure criterion implemented in ABAQUS is functioned by me...
CEAS Aeronautical Journal, 2013
Chemie Ingenieur Technik, 2010
CEAS Aeronautical Journal, 2013