Gangadhara Prusty | The University of New South Wales (original) (raw)

Papers by Gangadhara Prusty

Fatigue & Fracture of Engineering Materials & Structures, 2010

Experimental and analytical investigations for the low cycle-fatigue life prediction of Glass-Rei... more Experimental and analytical investigations for the low cycle-fatigue life prediction of Glass-Reinforced Polymer (GRP) in Chopped Strand Mat (CSM) form are studied. Based on the theories of modulus degradation and residual strength degradation, a novel model is proposed for the prediction of progressive stiffness loss in terms of tension–tension fatigue load and the number of cycles. The proposed model involves various loadings and environmental variables, which makes the reliable predictions suitable for structural analysts. Experiments were carried out at room and elevated temperatures to evaluate the validity of the proposed prediction model for the characterisation of temperature-dependent behaviour in fatigue. Predictions using the proposed model are in good agreement with the experiments that justify the use of the model to determine the extent of low-cycle fatigue damage accumulation in GRP–CSM at room and elevated temperatures.

International Journal of Mechanical Sciences, 2011

An improved third order shear deformation theory is employed to investigate thermal buckling and ... more An improved third order shear deformation theory is employed to investigate thermal buckling and vibration of the functionally graded beams. A power law distribution is used to describe the variation of volume fraction of material compositions. The functionally graded material properties are assumed to vary smoothly and continuously across the thickness of the beams. The Ritz method is adopted to solve the eigenvalue problems that are associated with thermal buckling and vibration in various types of immovable boundary conditions. The parametric study covered in this paper includes the effects of material composition, temperature-dependent material properties, and slenderness ratio.

Composite Structures, 2008

Fracture mechanics-based predictive methodologies are commonly employed to estimate onset of inte... more Fracture mechanics-based predictive methodologies are commonly employed to estimate onset of interlaminar damage growth in composite structures. Full implementation of interlaminar fracture mechanics in design requires the continuing development of codes to calculate energy release rates and advancements in delamination growth criteria under mixed mode conditions. In this research, an analytical crack tip element (CTE) methodology was evaluated and applied to predict skin-to-stiffener separation, which is a typical failure mode in aerospace structures. The methodology was correlated against empirical data obtained from structural testing of a single blade stiffened panel with an embedded artificial debond. Failure initiation occurred at the location predicted by the CTE and the predicted load for initiation agreed with the average of a set of experimental results.

Composite Structures, 2004

Composites Part A-applied Science and Manufacturing, 2009

MicroCT scanning is a non-destructive inspection method which was used to visualise tow architect... more MicroCT scanning is a non-destructive inspection method which was used to visualise tow architecture in woven composites with the ultimate goal of three-dimensional model generation. This has been achieved in the past for glass fabric composites, but is problematic when applied to carbon fabrics. Using X-rays, it is difficult to discriminate between elements of the composite, particularly the region between co-aligned neighbouring tows. This presents difficulty when viewing such composites using X-ray MicroCT scanning. Additives were used to enhance contrast during scanning. The most successful techniques were coating of fabrics with gold, copper, and an iodine contrast agent. Resin particle additive techniques were also trialled, with limited success. Good visualisations of glass fabrics were possible without contrast enhancement. Three-dimensional reconstructions of interior tow architectures were then made from the scans of contrast enhanced specimens. This research can be viewed as a starting point in developing methods for generating contrast between neighbouring tows within a three-dimensional woven preform using MicroCT scanning.

International Journal of Fracture, 2008

The behaviour of a composite test specimen with an embedded delamination subjected to transverse ... more The behaviour of a composite test specimen with an embedded delamination subjected to transverse tension has been investigated through experimental testing and finite element (FE) analyses. The testing program consisted of specimens in two geometrical configurations; square and rectangular delamination. The initiation and growth of the delamination was numerically predicted by fracture mechanics. FE models were analysed with both MSC.Nastran and Abaqus FE codes. The MSC.Nastran model was used to calculate strain energy release rates employing a crack tip element methodology. The Abaqus model was evaluated using the virtual crack closure technique. Both approaches accurately predicted failure initiation locations as observed in the test specimens. Failure loads were also well predicted. The mode mix at the crack tip in the proposed specimen was found to be similar to the mode mix expected in a conventional in-plane compression specimen.

Finite Elements in Analysis and Design, 2007

A new approach for the large deflection analysis of isotropic and composite arbitrary orientated ... more A new approach for the large deflection analysis of isotropic and composite arbitrary orientated stiffened plates is presented. Non-linear equilibrium equations are derived using the principle of virtual work applied to a continuum with a total Lagrangian description of motion. Eight node isoparametric plate elements are combined with three node beam elements, using the concept of equal displacements at the plate-stiffener interface, to represent the stiffened plate. The stiffness of the beam element is computed first irrespective of its position within the plate element and then transferred to the plate nodes depending on its orientation and position within the plate element. The Newton-Raphson incrementaliterative solution technique is used to obtain the non-linear response path. Results obtained by the present approach are compared with those available in the open literature to demonstrate the validity and efficiency of the proposed approach and good agreement is found in all the investigated cases. ᭧

Composite Structures

A new multi-scale modelling approach is applied to specimen testing to define the critical strain... more A new multi-scale modelling approach is applied to specimen testing to define the critical strain invariants for the damage onset theory proposed by Gosse, Christensen and Hart-Smith. The onset theory is a micromechanics theory that uses critical strain invariants to predict the onset of damage within fiber polymer composites. To obtain the critical strain invariants for the matrix, finite element

Finite Elements in Analysis and Design, 2003

Analysis of composite sti ened panels used in aerospace, ship and other engineering structures by... more Analysis of composite sti ened panels used in aerospace, ship and other engineering structures by the method of ÿnite elements has been presented. The formulation presented is based on the concept of equal displacements at the shell-sti ener interface. An eight-noded isoparametric shell element is used in association with three-noded curved beam element for the formulation of the sti ened panel element. First-order shear deformation theory is used in the present study. The sti ness matrix of the sti ener is computed ÿrst irrespective of its position within the plate/shell element. The sti ness matrix so computed for the sti ener is then transferred to that of the plate/shell element nodes depending on its position and orientation within the element before assembling the element sti ness matrix. A generalised formulation for the hat-shaped sti ener is presented. The investigation is restricted to linear static analysis of composite sti ened panels and parametric studies have been made to study the various aspects of laminated composite shell with open and closed shaped sti eners. ?

Journal of Sound and Vibration, 2001

The present work describes the transient dynamic response of unstiffened/stiffened composite plat... more The present work describes the transient dynamic response of unstiffened/stiffened composite plates/shells using finite element method. Composite panels find wide applications in aerospace, marine and other engineering because of its high strength to weight ratios. These structures are often subjected to air-blast loading, underwater shock etc., which requires a thorough dynamic response analysis under such loading. A modified approach of shell and stiffener modelling is adopted here using an eight-noded isoparametric quadratic element for the shell and a three-noded curved stiffener element for the stiffeners on the concept of equal displacements at the shell-stiffener interface. The present formulation obviates the need for imposing the mesh line along the stiffeners; rather it accommodates the stiffeners elegantly anywhere placed arbitrarily inside the element with computational efficiency. Newmarks method for direct time integration has been adopted for the solution of the governing equation for undamped motion. The transient dynamic response of stiffened and unstiffened structures subjected to various kinds of time variant loading has been studied and the results are compared with the published ones.

Ocean Engineering, 2001

Static analysis of stiffened shells has been carried out using an eight-noded isoparametric eleme... more Static analysis of stiffened shells has been carried out using an eight-noded isoparametric element for the shell and a three-noded curved beam element for the stiffener. A same displacement function is used for the shell and the stiffener elements. A modified technique has been followed to analyse the shell, which is an improvement over the degenerated shell concept. The stiffness

Journal of Reinforced Plastics and Composites, 2005

Ocean Engineering, 2010

... But in designs such as keel attachments, the flange of the top hat stiffener is fastened to t... more ... But in designs such as keel attachments, the flange of the top hat stiffener is fastened to the hull using keel bolts, and most of the failures ... The laminate was manufactured by hand layup method where the foam core was glued to the base panel and layers of fibre mat were laid. ...

Fatigue & Fracture of Engineering Materials & Structures, 2007

Experimental investigation on E-glass/polyester chopped strand mat (CSM) composite laminates unde... more Experimental investigation on E-glass/polyester chopped strand mat (CSM) composite laminates under fatigue loading has been carried out. The laminated composites were exposed to fire for different exposure times up to a maximum of 20 minutes. Monotonic tensile and fatigue tests on standard specimens taken from the fire-exposed panels have been performed in tension-tension mode using INSTRON 8504 universal testing machine at the University of New South Wales, Sydney. The effects of fire exposure on the fatigue performance of the laminates are compared with the unburnt material. The results obtained from the extensive test program show that a short fire exposure could improve the fatigue performance of the E-glass/polyester CSM composite. However, in contrary to the observation on short fire exposure time, the effect of improving fatigue response diminishes quickly with further increase in fire exposure time. Additionally, the test data obtained are used to predict the fatigue life in association with an existing fatigue life model, developed by Caprino and D'Amore.1, 8

International Journal of Mechanical Sciences, 2008

The paper presents finite element free vibration and buckling analysis of laminated hat-stiffened... more The paper presents finite element free vibration and buckling analysis of laminated hat-stiffened shallow and deep shells using arbitrarily oriented stiffener formulation. Modified approach for modelling the curved stiffener is implemented using necessary transformations. A simplified stiffener formulation is presented to accommodate various shapes of stiffener shapes in developing the rigidity matrix for the finite element formulation. Investigation has been

Journal of Reinforced Plastics and Composites, 2005

Ships and Offshore Structures, 2010

This paper describes and demonstrates a method for the hydroelastic tailoring of flexible composi... more This paper describes and demonstrates a method for the hydroelastic tailoring of flexible composite marine propeller blades. This method is applicable to situations in which the propeller's shape adapts to changing flow conditions due to its rotation in a spatially varying wake, resulting in improved efficiency when compared to a rigid propeller. The unloaded shape of the flexible propeller and

International Journal of Crashworthiness, 2001

ABSTRACT In this article, a new three-dimensional finite element modeling approach with less comp... more ABSTRACT In this article, a new three-dimensional finite element modeling approach with less computing time and space is introduced to study the buckling behavior of sandwich panels, containing a face–core debond. The finite element model presented in this study relates the motion of the face sheets to the core through constraint equations utilizing the concept of slave and master nodes, thus representing a more realistic model of the sandwich panel. The composite face sheets are modeled with shell elements, and the core is modeled using the 3D structural solid elements capable of taking transverse flexibility into consideration. In order to model the debond, the constraints between the nodes of the face sheet and the core are removed and replaced with contact elements in the debonded region to avoid interpenetration. The model is validated through comparison with experimental results reported in the literature. The validated model is then used to study the effects of the size, shape, aspect ratio of the debond, as well as fiber orientation of the face sheets and the influence of core stiffness on the buckling load of the panel subject to different boundary conditions on the top and bottom face sheets of the panel.

Materials & Design

An improved third order shear deformation theory is employed to formulate a governing equation fo... more An improved third order shear deformation theory is employed to formulate a governing equation for predicting free vibration of layered functionally graded beams. The Ritz method is adopted to solve the governing equation for various types of boundary conditions and the frequency results are validated by some available and experimental results. A multi-step sequential infiltration technique is used to fabricate the layered functionally graded beams for vibration testing. For the first time, a simple mathematical model, based on a power law distribution, is introduced to approximate material volume fraction of the layered beams. The details of layered beam fabrication according to the infiltration technique, microstructure and volume fraction analysis as well as vibration experimental set up are included and described in this investigation. Aspects which affect natural frequencies, such as material compositions, thickness ratio, and boundary conditions, are then taken into consideration. The impact on frequency of added mass is presented and discussed.

Composites Part B-engineering, 2011

The performance of any approximation scheme is known to be largely dependent on the type of surro... more The performance of any approximation scheme is known to be largely dependent on the type of surrogate models and its corresponding input variables. Elastic modulus prediction of short fibre composites with polyester and vinylester is presented using the surrogate framework supported by multiple spatially distributed surrogate models of different types. Poisson’s ratio is included as an additional variable to predict

Fatigue & Fracture of Engineering Materials & Structures, 2010

Experimental and analytical investigations for the low cycle-fatigue life prediction of Glass-Rei... more Experimental and analytical investigations for the low cycle-fatigue life prediction of Glass-Reinforced Polymer (GRP) in Chopped Strand Mat (CSM) form are studied. Based on the theories of modulus degradation and residual strength degradation, a novel model is proposed for the prediction of progressive stiffness loss in terms of tension–tension fatigue load and the number of cycles. The proposed model involves various loadings and environmental variables, which makes the reliable predictions suitable for structural analysts. Experiments were carried out at room and elevated temperatures to evaluate the validity of the proposed prediction model for the characterisation of temperature-dependent behaviour in fatigue. Predictions using the proposed model are in good agreement with the experiments that justify the use of the model to determine the extent of low-cycle fatigue damage accumulation in GRP–CSM at room and elevated temperatures.

International Journal of Mechanical Sciences, 2011

An improved third order shear deformation theory is employed to investigate thermal buckling and ... more An improved third order shear deformation theory is employed to investigate thermal buckling and vibration of the functionally graded beams. A power law distribution is used to describe the variation of volume fraction of material compositions. The functionally graded material properties are assumed to vary smoothly and continuously across the thickness of the beams. The Ritz method is adopted to solve the eigenvalue problems that are associated with thermal buckling and vibration in various types of immovable boundary conditions. The parametric study covered in this paper includes the effects of material composition, temperature-dependent material properties, and slenderness ratio.

Composite Structures, 2008

Fracture mechanics-based predictive methodologies are commonly employed to estimate onset of inte... more Fracture mechanics-based predictive methodologies are commonly employed to estimate onset of interlaminar damage growth in composite structures. Full implementation of interlaminar fracture mechanics in design requires the continuing development of codes to calculate energy release rates and advancements in delamination growth criteria under mixed mode conditions. In this research, an analytical crack tip element (CTE) methodology was evaluated and applied to predict skin-to-stiffener separation, which is a typical failure mode in aerospace structures. The methodology was correlated against empirical data obtained from structural testing of a single blade stiffened panel with an embedded artificial debond. Failure initiation occurred at the location predicted by the CTE and the predicted load for initiation agreed with the average of a set of experimental results.

Composite Structures, 2004

Composites Part A-applied Science and Manufacturing, 2009

MicroCT scanning is a non-destructive inspection method which was used to visualise tow architect... more MicroCT scanning is a non-destructive inspection method which was used to visualise tow architecture in woven composites with the ultimate goal of three-dimensional model generation. This has been achieved in the past for glass fabric composites, but is problematic when applied to carbon fabrics. Using X-rays, it is difficult to discriminate between elements of the composite, particularly the region between co-aligned neighbouring tows. This presents difficulty when viewing such composites using X-ray MicroCT scanning. Additives were used to enhance contrast during scanning. The most successful techniques were coating of fabrics with gold, copper, and an iodine contrast agent. Resin particle additive techniques were also trialled, with limited success. Good visualisations of glass fabrics were possible without contrast enhancement. Three-dimensional reconstructions of interior tow architectures were then made from the scans of contrast enhanced specimens. This research can be viewed as a starting point in developing methods for generating contrast between neighbouring tows within a three-dimensional woven preform using MicroCT scanning.

International Journal of Fracture, 2008

The behaviour of a composite test specimen with an embedded delamination subjected to transverse ... more The behaviour of a composite test specimen with an embedded delamination subjected to transverse tension has been investigated through experimental testing and finite element (FE) analyses. The testing program consisted of specimens in two geometrical configurations; square and rectangular delamination. The initiation and growth of the delamination was numerically predicted by fracture mechanics. FE models were analysed with both MSC.Nastran and Abaqus FE codes. The MSC.Nastran model was used to calculate strain energy release rates employing a crack tip element methodology. The Abaqus model was evaluated using the virtual crack closure technique. Both approaches accurately predicted failure initiation locations as observed in the test specimens. Failure loads were also well predicted. The mode mix at the crack tip in the proposed specimen was found to be similar to the mode mix expected in a conventional in-plane compression specimen.

Finite Elements in Analysis and Design, 2007

A new approach for the large deflection analysis of isotropic and composite arbitrary orientated ... more A new approach for the large deflection analysis of isotropic and composite arbitrary orientated stiffened plates is presented. Non-linear equilibrium equations are derived using the principle of virtual work applied to a continuum with a total Lagrangian description of motion. Eight node isoparametric plate elements are combined with three node beam elements, using the concept of equal displacements at the plate-stiffener interface, to represent the stiffened plate. The stiffness of the beam element is computed first irrespective of its position within the plate element and then transferred to the plate nodes depending on its orientation and position within the plate element. The Newton-Raphson incrementaliterative solution technique is used to obtain the non-linear response path. Results obtained by the present approach are compared with those available in the open literature to demonstrate the validity and efficiency of the proposed approach and good agreement is found in all the investigated cases. ᭧

Composite Structures

A new multi-scale modelling approach is applied to specimen testing to define the critical strain... more A new multi-scale modelling approach is applied to specimen testing to define the critical strain invariants for the damage onset theory proposed by Gosse, Christensen and Hart-Smith. The onset theory is a micromechanics theory that uses critical strain invariants to predict the onset of damage within fiber polymer composites. To obtain the critical strain invariants for the matrix, finite element

Finite Elements in Analysis and Design, 2003

Analysis of composite sti ened panels used in aerospace, ship and other engineering structures by... more Analysis of composite sti ened panels used in aerospace, ship and other engineering structures by the method of ÿnite elements has been presented. The formulation presented is based on the concept of equal displacements at the shell-sti ener interface. An eight-noded isoparametric shell element is used in association with three-noded curved beam element for the formulation of the sti ened panel element. First-order shear deformation theory is used in the present study. The sti ness matrix of the sti ener is computed ÿrst irrespective of its position within the plate/shell element. The sti ness matrix so computed for the sti ener is then transferred to that of the plate/shell element nodes depending on its position and orientation within the element before assembling the element sti ness matrix. A generalised formulation for the hat-shaped sti ener is presented. The investigation is restricted to linear static analysis of composite sti ened panels and parametric studies have been made to study the various aspects of laminated composite shell with open and closed shaped sti eners. ?

Journal of Sound and Vibration, 2001

The present work describes the transient dynamic response of unstiffened/stiffened composite plat... more The present work describes the transient dynamic response of unstiffened/stiffened composite plates/shells using finite element method. Composite panels find wide applications in aerospace, marine and other engineering because of its high strength to weight ratios. These structures are often subjected to air-blast loading, underwater shock etc., which requires a thorough dynamic response analysis under such loading. A modified approach of shell and stiffener modelling is adopted here using an eight-noded isoparametric quadratic element for the shell and a three-noded curved stiffener element for the stiffeners on the concept of equal displacements at the shell-stiffener interface. The present formulation obviates the need for imposing the mesh line along the stiffeners; rather it accommodates the stiffeners elegantly anywhere placed arbitrarily inside the element with computational efficiency. Newmarks method for direct time integration has been adopted for the solution of the governing equation for undamped motion. The transient dynamic response of stiffened and unstiffened structures subjected to various kinds of time variant loading has been studied and the results are compared with the published ones.

Ocean Engineering, 2001

Static analysis of stiffened shells has been carried out using an eight-noded isoparametric eleme... more Static analysis of stiffened shells has been carried out using an eight-noded isoparametric element for the shell and a three-noded curved beam element for the stiffener. A same displacement function is used for the shell and the stiffener elements. A modified technique has been followed to analyse the shell, which is an improvement over the degenerated shell concept. The stiffness

Journal of Reinforced Plastics and Composites, 2005

Ocean Engineering, 2010

... But in designs such as keel attachments, the flange of the top hat stiffener is fastened to t... more ... But in designs such as keel attachments, the flange of the top hat stiffener is fastened to the hull using keel bolts, and most of the failures ... The laminate was manufactured by hand layup method where the foam core was glued to the base panel and layers of fibre mat were laid. ...

Fatigue & Fracture of Engineering Materials & Structures, 2007

Experimental investigation on E-glass/polyester chopped strand mat (CSM) composite laminates unde... more Experimental investigation on E-glass/polyester chopped strand mat (CSM) composite laminates under fatigue loading has been carried out. The laminated composites were exposed to fire for different exposure times up to a maximum of 20 minutes. Monotonic tensile and fatigue tests on standard specimens taken from the fire-exposed panels have been performed in tension-tension mode using INSTRON 8504 universal testing machine at the University of New South Wales, Sydney. The effects of fire exposure on the fatigue performance of the laminates are compared with the unburnt material. The results obtained from the extensive test program show that a short fire exposure could improve the fatigue performance of the E-glass/polyester CSM composite. However, in contrary to the observation on short fire exposure time, the effect of improving fatigue response diminishes quickly with further increase in fire exposure time. Additionally, the test data obtained are used to predict the fatigue life in association with an existing fatigue life model, developed by Caprino and D'Amore.1, 8

International Journal of Mechanical Sciences, 2008

The paper presents finite element free vibration and buckling analysis of laminated hat-stiffened... more The paper presents finite element free vibration and buckling analysis of laminated hat-stiffened shallow and deep shells using arbitrarily oriented stiffener formulation. Modified approach for modelling the curved stiffener is implemented using necessary transformations. A simplified stiffener formulation is presented to accommodate various shapes of stiffener shapes in developing the rigidity matrix for the finite element formulation. Investigation has been

Journal of Reinforced Plastics and Composites, 2005

Ships and Offshore Structures, 2010

This paper describes and demonstrates a method for the hydroelastic tailoring of flexible composi... more This paper describes and demonstrates a method for the hydroelastic tailoring of flexible composite marine propeller blades. This method is applicable to situations in which the propeller's shape adapts to changing flow conditions due to its rotation in a spatially varying wake, resulting in improved efficiency when compared to a rigid propeller. The unloaded shape of the flexible propeller and

International Journal of Crashworthiness, 2001

ABSTRACT In this article, a new three-dimensional finite element modeling approach with less comp... more ABSTRACT In this article, a new three-dimensional finite element modeling approach with less computing time and space is introduced to study the buckling behavior of sandwich panels, containing a face–core debond. The finite element model presented in this study relates the motion of the face sheets to the core through constraint equations utilizing the concept of slave and master nodes, thus representing a more realistic model of the sandwich panel. The composite face sheets are modeled with shell elements, and the core is modeled using the 3D structural solid elements capable of taking transverse flexibility into consideration. In order to model the debond, the constraints between the nodes of the face sheet and the core are removed and replaced with contact elements in the debonded region to avoid interpenetration. The model is validated through comparison with experimental results reported in the literature. The validated model is then used to study the effects of the size, shape, aspect ratio of the debond, as well as fiber orientation of the face sheets and the influence of core stiffness on the buckling load of the panel subject to different boundary conditions on the top and bottom face sheets of the panel.

Materials & Design

An improved third order shear deformation theory is employed to formulate a governing equation fo... more An improved third order shear deformation theory is employed to formulate a governing equation for predicting free vibration of layered functionally graded beams. The Ritz method is adopted to solve the governing equation for various types of boundary conditions and the frequency results are validated by some available and experimental results. A multi-step sequential infiltration technique is used to fabricate the layered functionally graded beams for vibration testing. For the first time, a simple mathematical model, based on a power law distribution, is introduced to approximate material volume fraction of the layered beams. The details of layered beam fabrication according to the infiltration technique, microstructure and volume fraction analysis as well as vibration experimental set up are included and described in this investigation. Aspects which affect natural frequencies, such as material compositions, thickness ratio, and boundary conditions, are then taken into consideration. The impact on frequency of added mass is presented and discussed.

Composites Part B-engineering, 2011

The performance of any approximation scheme is known to be largely dependent on the type of surro... more The performance of any approximation scheme is known to be largely dependent on the type of surrogate models and its corresponding input variables. Elastic modulus prediction of short fibre composites with polyester and vinylester is presented using the surrogate framework supported by multiple spatially distributed surrogate models of different types. Poisson’s ratio is included as an additional variable to predict