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1

Simulating progressive damage of notched composite laminates with various lamination schemes

Mandal B., Chakrabarti A.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 2

333--347

EN

A three dimensional finite element based progressive damage model has been developed for the failure analysis of notched composite laminates. The material constitutive relations and the progressive damage algorithms are implemented into finite element code ABAQUS using user-defined subroutine UMAT. The existing failure criteria for the composite laminates are modified by including the failure criteria for fiber/matrix shear damage and delamination effects. The proposed numerical model is quite efficient and simple compared to other progressive damage models available in the literature. The efficiency of the present constitutive model and the computational scheme is verified by comparing the simulated results with the results available in the literature. A parametric study has been carried out to investigate the effect of change in lamination scheme on the failure behaviour of notched composite laminates.

2

Static, vibration and buckling analysis of skew composite and sandwich plates under thermo mechanical loading

Singh S. K., Chakrabarti A.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 3

887--898

EN

Static, vibration and buckling behavior of laminated composite and sandwich skew plates is studied using an efficient C0 FE model developed based on refined higher order zigzag theory. The C0 FE model satisfies the interlaminar shear stress continuity at the interfaces and zero transverse shear stress conditions at plate top and bottom. In this model, the first derivatives of transverse displacement have been treated as independent variables to overcome the problem of C1 continuity associated with the plate theory. The C0 continuity of the present element is compensated in the stiffness matrix formulation by adding a suitable term. In order to avoid stress oscillations observed in the displacement based finite element, the stress field derived from temperature is made consistent with the total strain field by using field consistent approach. Numerical results are presented for different static, vibration and buckling problems by applying the FE model under thermo mechanical loading, where a nine noded C0 continuous isoparametric element is used. It is observed that there are very few results available in the literature on laminated composite and sandwich skew plates based on refined theories. As such many new results are also generated for future reference.

3

A new C0 2D FE model based on improved higher order zigzag theory for the analysis of soft core sandwich plate

Khandelwal R. P., Chakrabarti A., Bhargava P.

International Journal of Applied Mechanics and Engineering

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2013

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Vol. 18, no. 2

395--423

EN

An efficient C0 continuous finite element (FE) model is developed based on a combined theory (refine higher order shear deformation theory (RHSDT) and least square error (LSE) method) for the static analysis of a soft core sandwich plate. In this (RHSDT) theory, the in-plane displacement field for the face sheets and the core is obtained by superposing a global cubically varying displacement field on a zig-zag linearly varying displacement field with a different slope in each layer. The transverse displacement assumes to have a quadratic variation within the core and it remains constant in the faces beyond the core. The proposed model satisfies the condition of transverse shear stress continuity at the layer interfaces and the zero transverse shear stress condition at the top and bottom of the sandwich plate. The nodal field variables are chosen in an efficient manner to circumvent the problem of C1 continuity requirement of the transverse displacements. In order to calculate the accurate through thickness transverse stresses variation, the Least Square Error (LSE) method has been used at the post processing stage. The proposed combined model (RHSDT and LSE) is implemented to analyze the laminated composites and sandwich plates. Many new results are also presented which should be useful for future research.

4

Behavior of eccentrically loaded rcc columns confined with frp sheets

Chakrabarti A., Bhargava P.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 4

943-958

EN

A nonlinear finite element model is developed for the analysis of an RCC (reinforced concrete column) confined by FRP (fiber - reinforced polymers) sheets and subjected to eccentric loading. A practical design of FRP confined concrete columns requires an accurate estimate of the performance enhancement due to the confinement mechanism under eccentric loading. Therefore, a confinement model is developed which relates the confined concrete strength with the unconfined concrete strength. In the present study, a 3-D finite element model is developed using the finite element software, ANSYS for the analysis of an FRP confined reinforced concrete circular column under axial and eccentric loading. The effects of four important parameters are studied in the present work: namely, the unconfined concrete strength, FRP thickness with different layer orientation, orthotropic properties of FRP and orientation of FRP fibers. The study focused on some interesting effects of these parameters on the confinement effectiveness of eccentrically loaded reinforced concrete columns. Many new results are generated which should be useful for future references.

5

Damage initiation of laminated FRP composite plates under impact

Chakrabarti A., Ashraf Iqbal M., Agrawal P.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 3

659-682

EN

The behaviour of composite laminates is not yet well understood under various impact loadings. Matrix cracking and delamination are the most common damage mechanisms in laminated fiber reinforced composite structures under impact. These damages are very difficult to detect by inspection from outside but they may cause a serious decrease in material strength and stiffness at the time of production, maintenance and due to small particle crashing to composite body. In this study, an efficient Finite Element Analysis model is developed in order to simulate initiation of damage in laminated composite plates under transverse impact loading considering different failure mechanisms. Hashin's failure model is incorporated into ABAQUS/Explicit for the present purpose. The influence of impactor velocity, thickness of plates and different stacking sequences is investigated for the initiation of damage in laminated composite plates under impact loading. Many new useful results are presented to show the variation of contact force, displacement, energy and stress resultants with time.