Genevieve Langdon | University of Cape Town (original) (raw)
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Papers by Genevieve Langdon
Int J Impact Engineering
This three-part article presents the results of experimental, analytical and numerical studies on... more This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reported on the experimental investigations, whilst the analytical modelling considerations were examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action. r
J Sandwich Structures and Materials
The results of blast tests on sandwich panels with honeycomb cores are reported. Two core heights... more The results of blast tests on sandwich panels with honeycomb cores are reported. Two core heights (13 mm and 25 mm) and two face sheet materials (glass fiber epoxy composite and aluminum alloy) were investigated. Increasing the core thickness reduced the permanent displacements exhibited by the sandwich panels. The panels with composite face sheets also exhibited smaller residual displacements than the aluminum face sheet counterparts. Damage took the form of core crushing, core shearing, debonding of the face sheet from the core, permanent displacement, cracking of the composite face sheets, and tearing. Higher damage levels were observed at elevated impulse levels. Load localization was found to concentrate the damage to the central portion of the panel, preventing the whole panel being employed in resisting the blast. experimental investigations [1-3] and theoretical analyses [4-6] being performed. Recently, sandwich structures consisting of two plates separated by a core material have been suggested as potential alternatives to monolithic plates for absorbing energy and managing the impulse associated with blast loading. The study of sandwich structures subjected to blast loading is a rapidly expanding area of activity. Examples of relevant work include analytical modeling by Fleck and Deshpande [7], finite element modeling by Xue and Hutchinson [8], and experiments by Dharmasena et al. [9] that indicate that advanced sandwich structures offer potential advantages over monolithic plates of equivalent mass. For further information, the interested reader is directed to a short review by Zhu and Lu [10] on the blast and impact loading of metallic and sandwich structures, or more detailed review of sandwich panels subjected to blast loading by Yuen et al. .
J Sandwich structures and Materials
Lattice structures based on two simple architectures have been manufactured from 316L stainless s... more Lattice structures based on two simple architectures have been manufactured from 316L stainless steel using the selective laser melting process. The compressive properties of structures based on a body-centered cubic (BCC) and a similar structure with vertical pillars (BCC-Z) were initially investigated at quasi-static rates of strain. Blast tests were subsequently performed on the lattice structures as well as on lattice sandwich structures with CFRP skins. When subjected to quasi-static compression loading, the BCC structure exhibited a progressive mode of failure, whereas the BCC-Z lattice deformed in a buckling-dominated mode of collapse. The blast response of the lattice cubes exhibited a linear dependency on the applied impulse up to the threshold for material densification. Relationships between the blast resistance and both the yield stress and energy absorption characteristics of the lattices have been established and an examination of the failed samples indicated that the collapse modes were similar in both the quasi-static and blast-loaded samples. Finally, the failure modes observed in the blast-loaded sandwich panels were investigated and found to be similar to those observed in the lattice blocks. Downloaded from Recently, there has been a growing interest in the use of lightweight metallic foams in high-performance load-bearing applications as well as protective structures resistant to explosive blast loading. It has been shown that metal foams offer many desirable properties, including superior sound proofing characteristics, electromagnetic wave shielding, low thermal conductivity, low toxicity, and excellent toughness retaining key mechanical properties up to temperatures of 300 C. These metallic foam structures are not without their drawbacks. The cell structure of the foam is very irregular, leading to localized damage at points of intrinsic weakness, and thus over-conservative design. It has been shown that the cell wall in such foams deforms by bending, rather than the more desirable stretching-dominated mode of deformation [1]. Recently, researchers have shown that it is possible to design other core architectures that offer greater strength and stiffness to weight ratios than those offered by foam structures . Sypeck [7] presented a detailed review of cellular structures, including aluminium foams, honeycombs, miniature truss, and metal textile laminates describing the different routes for manufacture. The design guide for metal foams [8] offers a valuable insight into the manufacture, properties, and uses of various foams. The guide shows that the quality of foam can greatly vary in quality and price. In spite of this, they showed that such foams are suitable for a wide range of applications from sandwich cores, damping and vibration control, thermal and acoustic management, bio-compatible inserts, and energy absorption.
This paper reports on experimental and numerical investigations into the response of flexible san... more This paper reports on experimental and numerical investigations into the response of flexible sandwich-type panels when subjected to blast loading. The response of sandwich-type panels with steel plates and polystyrene cores are compared to panels with steel face plates and aluminium honeycomb cores. Panels are loaded by detonating plastic explosive discs in close proximity to the front face of the panel. The numerical model is used to explain the stress attenuation and enhancement of the panels with different cores when subjected to blast induced dynamic loading. The permanent deflection of the back plate is determined by the velocity attenuation properties (and hence the transmitted stress pulse) of the core. Core efficiency in terms of energy absorption is an important factor for thicker cores. For panels of comparable mass, those with aluminium honeycomb cores perform ''better" than those with polystyrene cores.
The effect of stand-off distance and charge mass on the response of fully clamped circular mild s... more The effect of stand-off distance and charge mass on the response of fully clamped circular mild steel plates, of radius 53 mm, subjected to blast loads travelling along tubular structures is reported. The procedure consists of creating a blast load using plastic explosive mounted onto the end of mild steel tubes. The stand-off distance is varied, from 13 mm to 300 mm, using different tube lengths.
This paper reports on an investigation into the behaviour of circular sandwich panels with alumin... more This paper reports on an investigation into the behaviour of circular sandwich panels with aluminium honeycomb cores subjected to air blast loading. Explosive tests were performed on sandwich panels consisting of mild steel face plates and aluminium honeycomb cores. The loading was generated by detonating plastic explosives at a pre-determined stand-off distance. Core height and face plate thickness were varied and the results are compared with previous experiments. It was observed that the panels exhibited permanent face plate deflection and tearing, and the honeycomb core exhibited crushing and densification. It was found that increasing the core thickness delayed the onset of core densification and decreased back plate deflection. Increasing the plate thickness was also found to decrease back plate deflection, although the panels then had a substantially higher overall mass.
In recent years the explosive loads have received considerable attention due to different events,... more In recent years the explosive loads have received considerable attention due to different events, accidental or intentional, that have occured over important structures all over the world. In consequence, in the last decade there was an important activity in the research of explosive loads. Initially, this works were mostly empirical, but, in the last years, important researches have begun to be developed. Much of this work has concentrated on the response of monolithic metal beams and plates to impulsive loads. In particular, a set of experimental tests about clamped circular mild steel plates, of radius 53 mm, subjected to blast loads travelling along tubular structures was carried out at the Blast Impact and Survivability Research Unit (BISRU, University of Cape Town). Some counter-intuitive results about incident impulse and plate response were observed in the experiments. The main objective of this paper is to study numerically the wave propagation in the tube used for the tests and to compare the response with that obtained experimentally. The effects of confinement, stand-off distance and charge mass on the reflected pressures and impulses are studied. The stand-off distance is varied from 25 to 300 mm, and the load masses are varied from 4 to 15 g. Finally, the effect of the reflection on the plate is also analyzed. The analysis shows satisfactory correlation with experimental results.
This three-part article presents the results of experimental, analytical and numerical studies on... more This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action. r
This three-part article presents the results of experimental, analytical and numerical studies on... more This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action. r
... Abstract Information. A voice for young scientists in South Africa. Journal Title: Quest; Vol... more ... Abstract Information. A voice for young scientists in South Africa. Journal Title: Quest; Volume: Volume 8; Issue: Issue 1; Publication Date: 2012; Pages: 22 - 23; Authors: Caradee Wright; Genevieve Langdon; Penny Moore; ISSN ...
European Journal of …, Jan 1, 2009
This paper investigates the blast response of fibre-metal laminates (FMLs) manufactured from two ... more This paper investigates the blast response of fibre-metal laminates (FMLs) manufactured from two glass fibre reinforced polypropylene composites and that of a plain aluminium alloy. The FMLs were manufactured by stacking the materials in a mould and applying heat and pressure to them. An autoclave was not used. In this work, attention focuses on elucidating the failure modes in the hybrid laminates. The blast data is non-dimensionalised to develop an empirical formula that characterises the behaviour of these materials under this extreme form of loading. The results indicate that thermoplastic-based FML materials may show potential for use in blast-resistant structures, due to their ability to absorb blast energy through delamination, debonding between the aluminium and composite layers, spalling/petalling of the aluminium, perforation through the layers and bending and stretching of the glass fibres. The tests also highlight the difference in response between panels constructed using woven (symmetrical response) and unidirectional (asymmetric behaviour) GFPP composites. The non-dimensional analysis appears to show that there is correlation between the response of all three panel types.
Int J Impact Engineering
This three-part article presents the results of experimental, analytical and numerical studies on... more This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reported on the experimental investigations, whilst the analytical modelling considerations were examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action. r
J Sandwich Structures and Materials
The results of blast tests on sandwich panels with honeycomb cores are reported. Two core heights... more The results of blast tests on sandwich panels with honeycomb cores are reported. Two core heights (13 mm and 25 mm) and two face sheet materials (glass fiber epoxy composite and aluminum alloy) were investigated. Increasing the core thickness reduced the permanent displacements exhibited by the sandwich panels. The panels with composite face sheets also exhibited smaller residual displacements than the aluminum face sheet counterparts. Damage took the form of core crushing, core shearing, debonding of the face sheet from the core, permanent displacement, cracking of the composite face sheets, and tearing. Higher damage levels were observed at elevated impulse levels. Load localization was found to concentrate the damage to the central portion of the panel, preventing the whole panel being employed in resisting the blast. experimental investigations [1-3] and theoretical analyses [4-6] being performed. Recently, sandwich structures consisting of two plates separated by a core material have been suggested as potential alternatives to monolithic plates for absorbing energy and managing the impulse associated with blast loading. The study of sandwich structures subjected to blast loading is a rapidly expanding area of activity. Examples of relevant work include analytical modeling by Fleck and Deshpande [7], finite element modeling by Xue and Hutchinson [8], and experiments by Dharmasena et al. [9] that indicate that advanced sandwich structures offer potential advantages over monolithic plates of equivalent mass. For further information, the interested reader is directed to a short review by Zhu and Lu [10] on the blast and impact loading of metallic and sandwich structures, or more detailed review of sandwich panels subjected to blast loading by Yuen et al. .
J Sandwich structures and Materials
Lattice structures based on two simple architectures have been manufactured from 316L stainless s... more Lattice structures based on two simple architectures have been manufactured from 316L stainless steel using the selective laser melting process. The compressive properties of structures based on a body-centered cubic (BCC) and a similar structure with vertical pillars (BCC-Z) were initially investigated at quasi-static rates of strain. Blast tests were subsequently performed on the lattice structures as well as on lattice sandwich structures with CFRP skins. When subjected to quasi-static compression loading, the BCC structure exhibited a progressive mode of failure, whereas the BCC-Z lattice deformed in a buckling-dominated mode of collapse. The blast response of the lattice cubes exhibited a linear dependency on the applied impulse up to the threshold for material densification. Relationships between the blast resistance and both the yield stress and energy absorption characteristics of the lattices have been established and an examination of the failed samples indicated that the collapse modes were similar in both the quasi-static and blast-loaded samples. Finally, the failure modes observed in the blast-loaded sandwich panels were investigated and found to be similar to those observed in the lattice blocks. Downloaded from Recently, there has been a growing interest in the use of lightweight metallic foams in high-performance load-bearing applications as well as protective structures resistant to explosive blast loading. It has been shown that metal foams offer many desirable properties, including superior sound proofing characteristics, electromagnetic wave shielding, low thermal conductivity, low toxicity, and excellent toughness retaining key mechanical properties up to temperatures of 300 C. These metallic foam structures are not without their drawbacks. The cell structure of the foam is very irregular, leading to localized damage at points of intrinsic weakness, and thus over-conservative design. It has been shown that the cell wall in such foams deforms by bending, rather than the more desirable stretching-dominated mode of deformation [1]. Recently, researchers have shown that it is possible to design other core architectures that offer greater strength and stiffness to weight ratios than those offered by foam structures . Sypeck [7] presented a detailed review of cellular structures, including aluminium foams, honeycombs, miniature truss, and metal textile laminates describing the different routes for manufacture. The design guide for metal foams [8] offers a valuable insight into the manufacture, properties, and uses of various foams. The guide shows that the quality of foam can greatly vary in quality and price. In spite of this, they showed that such foams are suitable for a wide range of applications from sandwich cores, damping and vibration control, thermal and acoustic management, bio-compatible inserts, and energy absorption.
This paper reports on experimental and numerical investigations into the response of flexible san... more This paper reports on experimental and numerical investigations into the response of flexible sandwich-type panels when subjected to blast loading. The response of sandwich-type panels with steel plates and polystyrene cores are compared to panels with steel face plates and aluminium honeycomb cores. Panels are loaded by detonating plastic explosive discs in close proximity to the front face of the panel. The numerical model is used to explain the stress attenuation and enhancement of the panels with different cores when subjected to blast induced dynamic loading. The permanent deflection of the back plate is determined by the velocity attenuation properties (and hence the transmitted stress pulse) of the core. Core efficiency in terms of energy absorption is an important factor for thicker cores. For panels of comparable mass, those with aluminium honeycomb cores perform ''better" than those with polystyrene cores.
The effect of stand-off distance and charge mass on the response of fully clamped circular mild s... more The effect of stand-off distance and charge mass on the response of fully clamped circular mild steel plates, of radius 53 mm, subjected to blast loads travelling along tubular structures is reported. The procedure consists of creating a blast load using plastic explosive mounted onto the end of mild steel tubes. The stand-off distance is varied, from 13 mm to 300 mm, using different tube lengths.
This paper reports on an investigation into the behaviour of circular sandwich panels with alumin... more This paper reports on an investigation into the behaviour of circular sandwich panels with aluminium honeycomb cores subjected to air blast loading. Explosive tests were performed on sandwich panels consisting of mild steel face plates and aluminium honeycomb cores. The loading was generated by detonating plastic explosives at a pre-determined stand-off distance. Core height and face plate thickness were varied and the results are compared with previous experiments. It was observed that the panels exhibited permanent face plate deflection and tearing, and the honeycomb core exhibited crushing and densification. It was found that increasing the core thickness delayed the onset of core densification and decreased back plate deflection. Increasing the plate thickness was also found to decrease back plate deflection, although the panels then had a substantially higher overall mass.
In recent years the explosive loads have received considerable attention due to different events,... more In recent years the explosive loads have received considerable attention due to different events, accidental or intentional, that have occured over important structures all over the world. In consequence, in the last decade there was an important activity in the research of explosive loads. Initially, this works were mostly empirical, but, in the last years, important researches have begun to be developed. Much of this work has concentrated on the response of monolithic metal beams and plates to impulsive loads. In particular, a set of experimental tests about clamped circular mild steel plates, of radius 53 mm, subjected to blast loads travelling along tubular structures was carried out at the Blast Impact and Survivability Research Unit (BISRU, University of Cape Town). Some counter-intuitive results about incident impulse and plate response were observed in the experiments. The main objective of this paper is to study numerically the wave propagation in the tube used for the tests and to compare the response with that obtained experimentally. The effects of confinement, stand-off distance and charge mass on the reflected pressures and impulses are studied. The stand-off distance is varied from 25 to 300 mm, and the load masses are varied from 4 to 15 g. Finally, the effect of the reflection on the plate is also analyzed. The analysis shows satisfactory correlation with experimental results.
This three-part article presents the results of experimental, analytical and numerical studies on... more This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action. r
This three-part article presents the results of experimental, analytical and numerical studies on... more This three-part article presents the results of experimental, analytical and numerical studies on the response of 1 4 scale stainless steel blast wall panels and connection systems. The panel design was based on a deep trough trapezoidal profile with welded angle connections top and bottom and free sides. The loading applied to the panel was a triangular pulse pressure representative of a gas explosion overpressure. The aim of this work was to investigate the influence of the connection detail on the overall performance of the panel/connection system under pulse pressure loading and to develop appropriate analytical and numerical models for correlation with the test results. Part I reports on the experimental investigations, whilst the analytical modelling considerations are examined in Part II. Finite element analysis, with ABAQUS, was used to simulate the blast wall panel behaviour and is discussed in Part III. Large permanent plastic deformations were produced in the panels without rupture, and localised buckling developed at the centre of the corrugations. The work highlights the importance of correctly modelling the support details and the variation in strength with blast direction (the blast wall panels being stronger in the design direction). The modelling approaches predict a design capacity that is 39% higher than the current design guidance predicts, as a result of modelling the supports and including membrane action. r
... Abstract Information. A voice for young scientists in South Africa. Journal Title: Quest; Vol... more ... Abstract Information. A voice for young scientists in South Africa. Journal Title: Quest; Volume: Volume 8; Issue: Issue 1; Publication Date: 2012; Pages: 22 - 23; Authors: Caradee Wright; Genevieve Langdon; Penny Moore; ISSN ...
European Journal of …, Jan 1, 2009
This paper investigates the blast response of fibre-metal laminates (FMLs) manufactured from two ... more This paper investigates the blast response of fibre-metal laminates (FMLs) manufactured from two glass fibre reinforced polypropylene composites and that of a plain aluminium alloy. The FMLs were manufactured by stacking the materials in a mould and applying heat and pressure to them. An autoclave was not used. In this work, attention focuses on elucidating the failure modes in the hybrid laminates. The blast data is non-dimensionalised to develop an empirical formula that characterises the behaviour of these materials under this extreme form of loading. The results indicate that thermoplastic-based FML materials may show potential for use in blast-resistant structures, due to their ability to absorb blast energy through delamination, debonding between the aluminium and composite layers, spalling/petalling of the aluminium, perforation through the layers and bending and stretching of the glass fibres. The tests also highlight the difference in response between panels constructed using woven (symmetrical response) and unidirectional (asymmetric behaviour) GFPP composites. The non-dimensional analysis appears to show that there is correlation between the response of all three panel types.