Prediction of through the width delamination growth in post-buckled laminates under fatigue loading using de-cohesive law

Hosseini-Toudeshky, Hossein,Goodarzi, M. Saeed,Mohammadi, Bijan Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

Initiation and growth of delamination is a great concern of designers of composite structures. Interface elements with de-cohesive constitutive law in the content of continuum damage mechanics can be used to predict initiation and growth of delamination in single and mixed mode conditions. In this paper, an interface element based on the cohesive zone method has been developed to simulate delaminatoin growth of post-buckled laminate under fatigue loading. The model was programmed as the user element and user material by the "User Programmable Features" in ANSYS finite element software. The interface element is a three-dimensional 20 node brick with small thickness. Because of mixed-mode condition of stress field at the delamination-front of post-buckled laminates, a mixed-mode bilinear constitutive law has been used as user material in this model. The constitutive law of interface element has been verified by modelling of a single element. A composite laminate with initial delamination under quasi-static compressive Loading available from literature has been remodeled with the present approach. Moreover, it will be shown that, the closer the delamination to the free surface of laminate, the slower the delamination growth under compressive fatigue loading. The effects of laminate configuration on delamination growth are also investigated.

Implementation of a micro-meso approach for progressive damage analysis of composite laminates

Hosseini-Toudeshky, H.,Farrokhabadi, A.,Mohammadi, B. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.5

The mismatch of ply orientations in composite laminates can cause high interlaminar stress concentrations near the free edges. Evaluation of these interlaminar stresses and their role in the progressive damage analysis of laminates is desirable. Recently, the authors developed a new method to relate the physically based micromechanics approach with the meso-scale CDM considering matrix cracking and induced delamination. In this paper, the developed method is applied for the analysis of edge effects in various angle-ply laminates such as $[10/-10]_{2s}$, $[30/-30]_{2s}$ and $[45/-45]_{2s}$ and comparing the results with available traditional CDM and experimental results. It is shown that the obtained stress-strain behaviors of laminates are in good agreement with the available experimental results and even in better agreement than the traditional CDM results. Variations of the stresses and stiffness components through the laminate thickness and near the free edges are also computed and compared with the available CDM results.

Sensor placement optimization for guided wave-based structural health monitoring

Hosseini-Toudeshky, Hossein,Amjad, Fazel Abdolrezaei Techno-Press 2021 Structural monitoring and maintenance Vol.8 No.2

Sensor placement optimization is an attempt to reduce the cost and enhance the detection performance in structural health monitoring (SHM) systems. This paper aims at studying sensor placement optimization for SHM systems. The attention is paid to lamb wave or guided wave-based SHM (GWSHM). By using detection theory and Bayes risk framework the expected cost (loss) of decision making or Bayes risk for SHM system is minimized and the optimal detector is derived. The global detection and false alarm rate are used for quantifying the detector performance. In this framework the sensor coverage, directionality and probabilities of damage occurrence are all accounted for. The effect of cross-correlation among actuator-sensor pairs is then considered by presenting an appropriate model for covariance structure. Applying the genetic algorithm, the global false alarm rate is minimized for a target global detection rate and different levels of correlation. In addition, the receiver-operating characteristic (ROC) is determined to analyze the effect of correlation on the system performance and optimal arrangement. For demonstration of the effect of cross-correlation on damage detection a numerical analysis is carried out using ABAQUS standard. Finally, it is concluded that by increasing the correlation among actuator-sensor pairs, the performance of the SHM system decreases.

Prediction of through the width delamination growth in post-buckled laminates under fatigue loading using de-cohesive law

Hossein Hosseini-Toudeshky,M. Saeed Goodarzi,Bijan Mohammadi 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.48 No.1

Initiation and growth of delamination is a great concern of designers of composite structures. Interface elements with de-cohesive constitutive law in the content of continuum damage mechanics can be used to predict initiation and growth of delamination in single and mixed mode conditions. In this paper, an interface element based on the cohesive zone method has been developed to simulate delaminatoin growth of post-buckled laminate under fatigue loading. The model was programmed as the user element and user material by the “User Programmable Features” in ANSYS finite element software. The interface element is a three-dimensional 20 node brick with small thickness. Because of mixed-mode condition of stress field at the delamination-front of post-buckled laminates, a mixed-mode bilinear constitutive law has been used as user material in this model. The constitutive law of interface element has been verified by modelling of a single element. A composite laminate with initial delamination under quasi-static compressive Loading available from literature has been remodeled with the present approach. Moreover, it will be shown that, the closer the delamination to the free surface of laminate, the slower the delamination growth under compressive fatigue loading. The effects of laminate configuration on delamination growth are also investigated.

Implementation of a micro-meso approach for progressive damage analysis of composite laminates

H. Hosseini-Toudeshky,A. Farrokhabadi,B. Mohammadi 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.5

The mismatch of ply orientations in composite laminates can cause high interlaminar stress concentrations near the free edges. Evaluation of these interlaminar stresses and their role in the progressive damage analysis of laminates is desirable. Recently, the authors developed a new method to relate the physically based micromechanics approach with the meso-scale CDM considering matrix cracking and induced delamination. In this paper, the developed method is applied for the analysis of edge effects in various angle-ply laminates such as [10/−10]2s, [30/−30]2s and [45/−45]2s and comparing the results with available traditional CDM and experimental results. It is shown that the obtained stress-strain behaviors of laminates are in good agreement with the available experimental results and even in better agreement than the traditional CDM results. Variations of the stresses and stiffness components through the laminate thickness and near the free edges are also computed and compared with the available CDM results.

Failure analysis of laminates by implementation of continuum damage mechanics in layer-wise finite element theory

Mohammadi, B.,Hosseini-Toudeshky, H.,Sadr-Lahidjani, M.H. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.6

In this paper a 3-D continuum damage mechanics formulation for composite laminates and its implementation into a finite element model that is based on the layer-wise laminate plate theory are described. In the damage formulation, each composite ply is treated as a homogeneous orthotropic material exhibiting orthotropic damage in the form of distributed microscopic cracks that are normal to the three principal material directions. The progressive damage of different angle ply composite laminates under quasi-static loading that exhibit the free edge effects are investigated. The effects of various numerical modeling parameters on the progressive damage response are investigated. It will be shown that the dominant damage mechanism in the lay-ups of [+30/-30]s and [+45/-45]s is matrix cracking. However, the lay-up of [+15/-15] may be delaminated in the vicinity of the edges and at $+{\theta}/-{\theta}$ layers interfaces.

Failure analysis of laminates by implementation of continuum damage mechanics in layer-wise finite element theory

B. Mohammadi,H. Hosseini-Toudeshky,M.H. Sadr-Lahidjani 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.6

In this paper a 3-D continuum damage mechanics formulation for composite laminates and its implementation into a finite element model that is based on the layer-wise laminate plate theory are described. In the damage formulation, each composite ply is treated as a homogeneous orthotropic material exhibiting orthotropic damage in the form of distributed microscopic cracks that are normal to the three principal material directions. The progressive damage of different angle ply composite laminates under quasi-static loading that exhibit the free edge effects are investigated. The effects of various numerical modeling parameters on the progressive damage response are investigated. It will be shown that the dominant damage mechanism in the lay-ups of [+30/-30]s and [+45/-45]s is matrix cracking. However, the lay-up of [+15/-15] may be delaminated in the vicinity of the edges and at +θ/-θ layers interfaces.

Modified DEBA for determining size dependent shear fracture energy of laminates

M. Saeed Goodarzi,Hossein Hosseini-Toudeshky 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.1

It has been argued that fracture energy of composite laminates depends on their thickness and number of layers. In this paper a modified direct energy balance approach (DEBA) has been developed to evaluate the mode-II shear fracture energy for E-glass/Epoxy laminates from finite element model at an arbitrary thickness. This approach considers friction and damage/plasticity deformations using cohesive zone modeling (CZM) and nonlinear finite element modeling. The presence of compressive stress and resulting friction was argued to be a possible cause for the thickness dependency of fracture energy. In the finite element modeling, CZM formulation has been developed with bilinear cohesive constitutive law combined with friction consideration. Also ply element have been developed with shear plastic damage model. Modified direct energy balance approach has been proposed for estimation of mode-II shear fracture energy. Experiments were performed on laminates of glass epoxy specimens for characterization of material parameters and determination of mode-II fracture energies for different thicknesses. Effect of laminate thickness on fracture energy of transverse crack tension (TCT) and end notched flexure (ENF) specimens has been numerically studied and comparison with experimental results has been made. It is shown that the developed numerical approach is capable of estimating increase in fracture energy due to size effect.

Compression failure and fiber-kinking modelingof laminated composites

A. Kabiri Ataabadi,S. Ziaei-Rad,H. Hosseini-Toudeshky 국제구조공학회 2012 Steel and Composite Structures, An International J Vol.12 No.1

In this study, the physically-based failure models for matrix and fibers in compression and tension loading are introduced. For the 3D stress based fiber kinking model a modification is proposed for calculation of the fiber misalignment angle. All of these models are implemented into the finite element code by using the advantage of damage variable and the numerical results are discussed. To investigate the matrix failure model, purely in-plane transverse compression experiments are carried out on the specimens made by Glass/Epoxy to obtain the fracture surface angle and then a comparison is made with the calculated numerical results. Furthermore, shear failure of (±45)s model is investigated and the obtained numerical results are discussed and compared with available experimental results. Some experiments are also carried out on the woven laminated composites to investigate the fracture pattern in the matrix failure mode and shown that the presented matrix failure model can be used for the woven composites. Finally, the obtained numerical results for stress based fiber kinking model and improved ones (strain based model) are discussed and compared with each other and with the available results. The results show that these models can predict the kink band angle approximately.