Shuguang Li - Academia.edu (original) (raw)

Papers by Shuguang Li

Research paper thumbnail of Finite Element Modelling of Composite Repair in Offshore Pipe Riser

Advanced Materials Research, 2012

The effects of coupled internal pressure and external tension on corroded offshore pipe riser rep... more The effects of coupled internal pressure and external tension on corroded offshore pipe riser repaired with a designated laminate orientation of carbon/epoxy (C/E) and E-glass/epoxy (EG/E) fibre reinforced composite (FRC) was evaluated. The steel riser (API 5L X60) was characterised through Ramberg-Osgood model while input data of the composites were extracted from those used as benchmark for analysis in the first world-wide failure exercise (WWFE) [1, 2]. It was found that the C/E composite provides superiority over the EG/E and laminates with a dedicated orientation is capable of enhancing the performance of risers subjected to the coupled loadings.

Research paper thumbnail of Burst strength of carbon fibre reinforced polyethylene strip pipeline repair system – a numerical and experimental approach

Journal of Composite Materials, 2014

Oil and gas pipelines are susceptible to various forms of damage where repair mechanisms have sin... more Oil and gas pipelines are susceptible to various forms of damage where repair mechanisms have since been developed for rehabilitation. Once installed, structural health monitoring often incurs excessive costs and defects rectification of the repaired pipeline becomes a major challenge. Finite element analysis (FEA) provides a rapid route to predict the behaviour of the rehabilitated pipelines under prescribed in-service conditions. In this paper, burst strength of a commercially available composite sleeve repair system, Helicoid Epoxy Sleeve (HES)™, which combines the use of carbon fibre strip and epoxy grout as reinforcement to damaged pipe, was investigated through experimental and numerical approaches. Design standards for subsea pipelines are used in the calculation of design pressure and burst pressure. In the experimental setup, API 5L X52 steel pipe was machined with 50% metal loss defect in wall thickness to simulate external corrosion. Results from design calculations, expe...

Research paper thumbnail of Establishing size effects in discontinuous fibre composites using 2D finite element analysis

Computational Materials Science, 2012

ABSTRACT Size effects are observed within discontinuous fibre composites, such that the material ... more ABSTRACT Size effects are observed within discontinuous fibre composites, such that the material properties change with the specimen volume. Representative volume elements (RVEs) are commonly used to simulate random fibre architectures for finite element analysis of discontinuous fibre composites. A series of simplified 2D RVE models have been created and studied in this paper, in order to determine the relationship between the critical RVE size and fibre length and volume fraction. All models are subjected to periodic boundary conditions, but average properties are extracted from an inner region offset from the model boundary by a distance equivalent to two fibre lengths. According to Saint–Venant’s principle, this offset removes the uncertainty associated with the approximate boundary conditions. A statistical stopping criterion has been adopted to determine the number of realisations required to achieve a representative set of elastic properties for each fibre architecture. The critical RVE side length is shown to be approximately four times the fibre length when considering convergence of the tensile and shear stiffnesses for the range of fibre lengths and volume fractions studied.

Research paper thumbnail of Integrated thermal, micro- and macro-mechanical modelling of post-fire flexural behaviour of flame-retarded glass/epoxy composites

Computational Materials Science, 2012

This paper presents an integrated modelling approach for the post-thermal exposure flexural behav... more This paper presents an integrated modelling approach for the post-thermal exposure flexural behaviour of glass fibre-reinforced (GFR) epoxy composites with/without flame retardants at both material and structural levels. This numerical model incorporates the outcomes from ...

Research paper thumbnail of Representative volume elements for discontinuous carbon fibre composites – Part 2: Determining the critical size

Composites Science and Technology, 2012

This is the second part in a series of papers investigating the size of representative volume ele... more This is the second part in a series of papers investigating the size of representative volume elements for discontinuous carbon fibre composites. An 'embedded cell' finite element approach, outlined in Part 1, has been used to determine critical RVE sizes for materials with increasing fibre lengths and fibre volume fractions. Convergence of the results for mechanical properties were seen at RVE edge lengths of four times the fibre length (a/L = 4), irrespective of the fibre volume fraction. The calculated Poisson's ratios (v 12 and v 21) were largely independent of the RVE size. The critical RVE size is seen to be dependent on deterministic size effects and statistical size effects. Deterministic size effects are dominant for RVE sizes smaller than a/L = 4 because of the presence of bridging fibres. Statistical size effects beyond a/L = 4 were seen to be principally dependant on the level of fibre homogeneity and the departure from isotropy within the RVE, and these aspects were evaluated. An analytical model has been used to extrapolate the variance data to understand the most computationally efficient way of determining the critical RVE size. This study confirmed that it is more efficient to test fewer larger models than many smaller models, for the same level of statistical confidence (95%).

Research paper thumbnail of Use of Upper and Lower Bound Theorem for 3D Stitched Composites

Research paper thumbnail of On the vectorial nature of the rotational degrees of freedom in spatial beam elements

Computers & Structures, 1996

ABSTRACT

Research paper thumbnail of Energy release rates for transverse cracking and delaminations induced by transverse cracks in laminated composites

Composites Part A: Applied Science and Manufacturing, 2005

Transversely cracked laminates have been analysed under a generalised plane strain condition whic... more Transversely cracked laminates have been analysed under a generalised plane strain condition which provides a better representation of the problem than a plane stress or plane strain condition as often employed in the literature. The energy release rates corresponding to two typical modes of damage, further transverse cracking and delamination induced by existing transverse cracks, have been evaluated. It has

Research paper thumbnail of A representative volume element based on translational symmetries for FE analysis of cracked laminates with two arrays of cracks

International Journal of Solids and Structures, 2009

A methodology is proposed for the construction of a representative volume element (RVE) for analy... more A methodology is proposed for the construction of a representative volume element (RVE) for analysis of laminated composites containing two arrays of ply cracks running in different directions. The only requirement is that the cracks in any ply are uniformly spaced, and if more than one ply of a given orientation is cracked, then the crack spacing of individual plies must only be in exact multiples of each other. The spacing of cracks in the two directions can be fully independent. The RVE is constructed through a systematic consideration of translational symmetries present in the cracked laminate. As a result, the boundary conditions on the RVE can be imposed without compromising accuracy. Examples of the application of the RVE methodology are given to illustrate its broad capability and a finite element (FE) stress analysis is performed for these cases to illustrate results such as the crack surface displacements, local stress fields and RVE-averaged elastic properties. For one case, the average properties are compared with experimental results, showing good agreement.

Research paper thumbnail of On the unit cell for micromechanical analysis of fibre-reinforced composites

Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 1999

Abstract This paper is concerned with the unit cell for micromechanical analyses of unidirectiona... more Abstract This paper is concerned with the unit cell for micromechanical analyses of unidirectionally fibre-reinforced composites. A systematic consideration has been made to the symmetries present in idealised fibre-matrix systems. The symmetries enable the ...

Research paper thumbnail of Computational Characterisation of FRC Using Micromechanical FEA Based on Appropriate Unit Cells

ICCES: International Conference on Computational & Experimental Engineering and Sciences, Apr 1, 2011

Research paper thumbnail of Variational approach based cracked laminate analyses revisited

Research paper thumbnail of Reduction of transverse shear stiffnesses of transversely cracked laminates

Research paper thumbnail of Displacement based finite strip Analysis of a cracked laminate with appropriate boundary condition formulation

Research paper thumbnail of A finite element study of the influence of coupled loadings on offshore pipe riser repaired with fibre reinforced composite

The effects of coupled loadings on three conditions of off-shore pipe riser, bare un-corroded, co... more The effects of coupled loadings on three conditions of off-shore pipe riser, bare un-corroded, corroded unrepaired and corroded repaired with a designated laminate orientation of carbon/epoxy (C/E) and E-glass/epoxy (EG/E) fibre reinforced composite (FRC) are studied. A computational procedure for simulating coupled internal pressure, longitudinal tensile and transverse bending on pipe riser was developed using a general purpose finite element code. The behaviour of the pipe riser was captured through the Ramberg-Osgood model. The composites laminate systems, a pre-cured prepreg and a wet-layup filament wounded composite were characterized with the aid of experimental data extracted from those used as benchmark for analysis in the first world-wide failure exercise (WWFE) [1, 2], The acceptable condition of the design loads was determined through a limit analysis known as the double-elastic slope method. The results revealed that pipe riser subjected to coupled hoop, tensile and bend...

Research paper thumbnail of Variation-based cracked laminate analysis revisited and fundamentally extended

International Journal of Solids and Structures, 2009

The analyses of cracked laminates based on a variational principle and related approaches are app... more The analyses of cracked laminates based on a variational principle and related approaches are appraised in this paper. The limitations of the existing methodology on the analyses of more general laminate configurations have been identified. It has been revealed that the limiting factor is the lack of boundary conditions for uncracked laminae. Natural boundary conditions have then been derived from the variational principle to meet the need. Such boundary conditions are mathematically sound but cannot be simply interpreted from the physical construction of the problem intuitively. A well posed boundary value problem has thus been formulated for laminates containing however many cracked and uncracked laminae. Appropriate mathematical tools can then be employed to solve the boundary value problem. The capability of analysing cracked laminates has been enhanced significantly, as a result.

Research paper thumbnail of An Analysis of Filament Overwound Toroidal Pressure Vessels and Optimum Design of Such Structures

Journal of Pressure Vessel Technology, 2002

This paper is concerned with the membrane shell analysis of filament overwound toroidal pressure ... more This paper is concerned with the membrane shell analysis of filament overwound toroidal pressure vessels and optimum design of such pressure vessels using the results of the analysis by means of mathematical nonlinear programming. The nature of the coupling between overwind and linear has been considered based on two extreme idealizations. In the first, the overwind is rigidly coupled with the liner, so that the two deform together in the meridional direction as the vessel dilates. In the second, the overwind is free to slide relative to the linear, but the overall elongations of the two around a meridian are identical. Optimized designs with the two idealizations show only minor differences, and it is concluded that either approximation is satisfactory for the purposes of vessel design. Aspects taken into account are the intrinsic overwind thickness variation arising from the winding process and the effects of fiber pre-tension. Pre-tension can be used not only to defer the onset o...

Research paper thumbnail of Discussion of “ Effect of Axial Compressibility on Buckling of Columns ” by Charles W. Bert (March, 1990, Vol. 116, No. 3)

Journal of Engineering Mechanics, 1991

Research paper thumbnail of Rigidities of One-Dimensional Laminates of Composite Materials

Journal of Engineering Mechanics, 1996

This note derives systematically the expressions of the stiffnesses and rigidities of one-dimensi... more This note derives systematically the expressions of the stiffnesses and rigidities of one-dimensional laminates. Various forms are obtained as a result of different assumptions introduced. Each form is applicable only when the assumptions are reasonably satisfied. While a complete account on this is not available, misleading applications can be found in the literature. It is the purpose of this note to bring a complete understanding of the problem so that different forms of the rigidities of one-dimensional laminates can be used correctly according to the practical service conditions of the components.

Research paper thumbnail of The centre of twist for a prismatic bar under free torsion

International Journal of Mechanical Engineering Education, 2003

ABSTRACT

Research paper thumbnail of Finite Element Modelling of Composite Repair in Offshore Pipe Riser

Advanced Materials Research, 2012

The effects of coupled internal pressure and external tension on corroded offshore pipe riser rep... more The effects of coupled internal pressure and external tension on corroded offshore pipe riser repaired with a designated laminate orientation of carbon/epoxy (C/E) and E-glass/epoxy (EG/E) fibre reinforced composite (FRC) was evaluated. The steel riser (API 5L X60) was characterised through Ramberg-Osgood model while input data of the composites were extracted from those used as benchmark for analysis in the first world-wide failure exercise (WWFE) [1, 2]. It was found that the C/E composite provides superiority over the EG/E and laminates with a dedicated orientation is capable of enhancing the performance of risers subjected to the coupled loadings.

Research paper thumbnail of Burst strength of carbon fibre reinforced polyethylene strip pipeline repair system – a numerical and experimental approach

Journal of Composite Materials, 2014

Oil and gas pipelines are susceptible to various forms of damage where repair mechanisms have sin... more Oil and gas pipelines are susceptible to various forms of damage where repair mechanisms have since been developed for rehabilitation. Once installed, structural health monitoring often incurs excessive costs and defects rectification of the repaired pipeline becomes a major challenge. Finite element analysis (FEA) provides a rapid route to predict the behaviour of the rehabilitated pipelines under prescribed in-service conditions. In this paper, burst strength of a commercially available composite sleeve repair system, Helicoid Epoxy Sleeve (HES)™, which combines the use of carbon fibre strip and epoxy grout as reinforcement to damaged pipe, was investigated through experimental and numerical approaches. Design standards for subsea pipelines are used in the calculation of design pressure and burst pressure. In the experimental setup, API 5L X52 steel pipe was machined with 50% metal loss defect in wall thickness to simulate external corrosion. Results from design calculations, expe...

Research paper thumbnail of Establishing size effects in discontinuous fibre composites using 2D finite element analysis

Computational Materials Science, 2012

ABSTRACT Size effects are observed within discontinuous fibre composites, such that the material ... more ABSTRACT Size effects are observed within discontinuous fibre composites, such that the material properties change with the specimen volume. Representative volume elements (RVEs) are commonly used to simulate random fibre architectures for finite element analysis of discontinuous fibre composites. A series of simplified 2D RVE models have been created and studied in this paper, in order to determine the relationship between the critical RVE size and fibre length and volume fraction. All models are subjected to periodic boundary conditions, but average properties are extracted from an inner region offset from the model boundary by a distance equivalent to two fibre lengths. According to Saint–Venant’s principle, this offset removes the uncertainty associated with the approximate boundary conditions. A statistical stopping criterion has been adopted to determine the number of realisations required to achieve a representative set of elastic properties for each fibre architecture. The critical RVE side length is shown to be approximately four times the fibre length when considering convergence of the tensile and shear stiffnesses for the range of fibre lengths and volume fractions studied.

Research paper thumbnail of Integrated thermal, micro- and macro-mechanical modelling of post-fire flexural behaviour of flame-retarded glass/epoxy composites

Computational Materials Science, 2012

This paper presents an integrated modelling approach for the post-thermal exposure flexural behav... more This paper presents an integrated modelling approach for the post-thermal exposure flexural behaviour of glass fibre-reinforced (GFR) epoxy composites with/without flame retardants at both material and structural levels. This numerical model incorporates the outcomes from ...

Research paper thumbnail of Representative volume elements for discontinuous carbon fibre composites – Part 2: Determining the critical size

Composites Science and Technology, 2012

This is the second part in a series of papers investigating the size of representative volume ele... more This is the second part in a series of papers investigating the size of representative volume elements for discontinuous carbon fibre composites. An 'embedded cell' finite element approach, outlined in Part 1, has been used to determine critical RVE sizes for materials with increasing fibre lengths and fibre volume fractions. Convergence of the results for mechanical properties were seen at RVE edge lengths of four times the fibre length (a/L = 4), irrespective of the fibre volume fraction. The calculated Poisson's ratios (v 12 and v 21) were largely independent of the RVE size. The critical RVE size is seen to be dependent on deterministic size effects and statistical size effects. Deterministic size effects are dominant for RVE sizes smaller than a/L = 4 because of the presence of bridging fibres. Statistical size effects beyond a/L = 4 were seen to be principally dependant on the level of fibre homogeneity and the departure from isotropy within the RVE, and these aspects were evaluated. An analytical model has been used to extrapolate the variance data to understand the most computationally efficient way of determining the critical RVE size. This study confirmed that it is more efficient to test fewer larger models than many smaller models, for the same level of statistical confidence (95%).

Research paper thumbnail of Use of Upper and Lower Bound Theorem for 3D Stitched Composites

Research paper thumbnail of On the vectorial nature of the rotational degrees of freedom in spatial beam elements

Computers & Structures, 1996

ABSTRACT

Research paper thumbnail of Energy release rates for transverse cracking and delaminations induced by transverse cracks in laminated composites

Composites Part A: Applied Science and Manufacturing, 2005

Transversely cracked laminates have been analysed under a generalised plane strain condition whic... more Transversely cracked laminates have been analysed under a generalised plane strain condition which provides a better representation of the problem than a plane stress or plane strain condition as often employed in the literature. The energy release rates corresponding to two typical modes of damage, further transverse cracking and delamination induced by existing transverse cracks, have been evaluated. It has

Research paper thumbnail of A representative volume element based on translational symmetries for FE analysis of cracked laminates with two arrays of cracks

International Journal of Solids and Structures, 2009

A methodology is proposed for the construction of a representative volume element (RVE) for analy... more A methodology is proposed for the construction of a representative volume element (RVE) for analysis of laminated composites containing two arrays of ply cracks running in different directions. The only requirement is that the cracks in any ply are uniformly spaced, and if more than one ply of a given orientation is cracked, then the crack spacing of individual plies must only be in exact multiples of each other. The spacing of cracks in the two directions can be fully independent. The RVE is constructed through a systematic consideration of translational symmetries present in the cracked laminate. As a result, the boundary conditions on the RVE can be imposed without compromising accuracy. Examples of the application of the RVE methodology are given to illustrate its broad capability and a finite element (FE) stress analysis is performed for these cases to illustrate results such as the crack surface displacements, local stress fields and RVE-averaged elastic properties. For one case, the average properties are compared with experimental results, showing good agreement.

Research paper thumbnail of On the unit cell for micromechanical analysis of fibre-reinforced composites

Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences, 1999

Abstract This paper is concerned with the unit cell for micromechanical analyses of unidirectiona... more Abstract This paper is concerned with the unit cell for micromechanical analyses of unidirectionally fibre-reinforced composites. A systematic consideration has been made to the symmetries present in idealised fibre-matrix systems. The symmetries enable the ...

Research paper thumbnail of Computational Characterisation of FRC Using Micromechanical FEA Based on Appropriate Unit Cells

ICCES: International Conference on Computational & Experimental Engineering and Sciences, Apr 1, 2011

Research paper thumbnail of Variational approach based cracked laminate analyses revisited

Research paper thumbnail of Reduction of transverse shear stiffnesses of transversely cracked laminates

Research paper thumbnail of Displacement based finite strip Analysis of a cracked laminate with appropriate boundary condition formulation

Research paper thumbnail of A finite element study of the influence of coupled loadings on offshore pipe riser repaired with fibre reinforced composite

The effects of coupled loadings on three conditions of off-shore pipe riser, bare un-corroded, co... more The effects of coupled loadings on three conditions of off-shore pipe riser, bare un-corroded, corroded unrepaired and corroded repaired with a designated laminate orientation of carbon/epoxy (C/E) and E-glass/epoxy (EG/E) fibre reinforced composite (FRC) are studied. A computational procedure for simulating coupled internal pressure, longitudinal tensile and transverse bending on pipe riser was developed using a general purpose finite element code. The behaviour of the pipe riser was captured through the Ramberg-Osgood model. The composites laminate systems, a pre-cured prepreg and a wet-layup filament wounded composite were characterized with the aid of experimental data extracted from those used as benchmark for analysis in the first world-wide failure exercise (WWFE) [1, 2], The acceptable condition of the design loads was determined through a limit analysis known as the double-elastic slope method. The results revealed that pipe riser subjected to coupled hoop, tensile and bend...

Research paper thumbnail of Variation-based cracked laminate analysis revisited and fundamentally extended

International Journal of Solids and Structures, 2009

The analyses of cracked laminates based on a variational principle and related approaches are app... more The analyses of cracked laminates based on a variational principle and related approaches are appraised in this paper. The limitations of the existing methodology on the analyses of more general laminate configurations have been identified. It has been revealed that the limiting factor is the lack of boundary conditions for uncracked laminae. Natural boundary conditions have then been derived from the variational principle to meet the need. Such boundary conditions are mathematically sound but cannot be simply interpreted from the physical construction of the problem intuitively. A well posed boundary value problem has thus been formulated for laminates containing however many cracked and uncracked laminae. Appropriate mathematical tools can then be employed to solve the boundary value problem. The capability of analysing cracked laminates has been enhanced significantly, as a result.

Research paper thumbnail of An Analysis of Filament Overwound Toroidal Pressure Vessels and Optimum Design of Such Structures

Journal of Pressure Vessel Technology, 2002

This paper is concerned with the membrane shell analysis of filament overwound toroidal pressure ... more This paper is concerned with the membrane shell analysis of filament overwound toroidal pressure vessels and optimum design of such pressure vessels using the results of the analysis by means of mathematical nonlinear programming. The nature of the coupling between overwind and linear has been considered based on two extreme idealizations. In the first, the overwind is rigidly coupled with the liner, so that the two deform together in the meridional direction as the vessel dilates. In the second, the overwind is free to slide relative to the linear, but the overall elongations of the two around a meridian are identical. Optimized designs with the two idealizations show only minor differences, and it is concluded that either approximation is satisfactory for the purposes of vessel design. Aspects taken into account are the intrinsic overwind thickness variation arising from the winding process and the effects of fiber pre-tension. Pre-tension can be used not only to defer the onset o...

Research paper thumbnail of Discussion of “ Effect of Axial Compressibility on Buckling of Columns ” by Charles W. Bert (March, 1990, Vol. 116, No. 3)

Journal of Engineering Mechanics, 1991

Research paper thumbnail of Rigidities of One-Dimensional Laminates of Composite Materials

Journal of Engineering Mechanics, 1996

This note derives systematically the expressions of the stiffnesses and rigidities of one-dimensi... more This note derives systematically the expressions of the stiffnesses and rigidities of one-dimensional laminates. Various forms are obtained as a result of different assumptions introduced. Each form is applicable only when the assumptions are reasonably satisfied. While a complete account on this is not available, misleading applications can be found in the literature. It is the purpose of this note to bring a complete understanding of the problem so that different forms of the rigidities of one-dimensional laminates can be used correctly according to the practical service conditions of the components.

Research paper thumbnail of The centre of twist for a prismatic bar under free torsion

International Journal of Mechanical Engineering Education, 2003

ABSTRACT