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Stephen R. Hallett - One of the best experts on this subject based on the ideXlab platform.

  • numerical analysis of high velocity oblique impacts and Residual Tensile Strength of carbon epoxy laminates
    Composite Structures, 2021
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Stephen R. Hallett
    Abstract:

    Abstract This paper presents prediction of the high velocity, oblique impact response and quasi-static Residual Tensile Strength of thin [45/90/−45/0]2s carbon/epoxy laminates using finite element (FE) models. A High-Fidelity Finite Element Method (Hi-FEM) with an automated unit cell meshing technique was employed. The predicted impact damage, characterised by the extent of fibre failure and delamination area, was validated against results from gas-gun tests for a range of impact velocities. The numerical results captured the trend of increasing impact damage with impact energy as observed from the tests. Changes in projectile orientation before impact were shown to increase the extent of fibre failure at high impact energies, up by 38% in edge impact cases. The Residual Tensile Strength of the impacted laminates was then investigated, where the numerical results for edge-impacted laminates agreed with the test data within 8%. On the other hand, the Residual Strength modelling results of centre-impacted laminates were found to be unconservative, mainly due to the extent of fibre failure predicted during impact. Machined notches were also studied for their Residual Tensile Strength in comparison to impact induced damage. The predicted Strength of edge-notched laminates was found to be in close agreement with the experimental results for edge-impacted laminates, differing by an average of 9%.

  • Numerical analysis of high velocity, oblique impacts and Residual Tensile Strength of carbon/epoxy laminates
    Composite Structures, 2021
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Stephen R. Hallett
    Abstract:

    Abstract This paper presents prediction of the high velocity, oblique impact response and quasi-static Residual Tensile Strength of thin [45/90/−45/0]2s carbon/epoxy laminates using finite element (FE) models. A High-Fidelity Finite Element Method (Hi-FEM) with an automated unit cell meshing technique was employed. The predicted impact damage, characterised by the extent of fibre failure and delamination area, was validated against results from gas-gun tests for a range of impact velocities. The numerical results captured the trend of increasing impact damage with impact energy as observed from the tests. Changes in projectile orientation before impact were shown to increase the extent of fibre failure at high impact energies, up by 38% in edge impact cases. The Residual Tensile Strength of the impacted laminates was then investigated, where the numerical results for edge-impacted laminates agreed with the test data within 8%. On the other hand, the Residual Strength modelling results of centre-impacted laminates were found to be unconservative, mainly due to the extent of fibre failure predicted during impact. Machined notches were also studied for their Residual Tensile Strength in comparison to impact induced damage. The predicted Strength of edge-notched laminates was found to be in close agreement with the experimental results for edge-impacted laminates, differing by an average of 9%.

  • experimental investigation of high velocity oblique impact and Residual Tensile Strength of carbon epoxy laminates
    Composites Science and Technology, 2019
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Xiaodong Xu, D Nowell, Stephen R. Hallett
    Abstract:

    Abstract Composite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and Residual Tensile Strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the Residual Strength of impacted laminates was determined through quasi-static Tensile tests. The Residual Strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of Residual Strength.

  • Experimental investigation of high velocity oblique impact and Residual Tensile Strength of carbon/epoxy laminates
    Composites Science and Technology, 2019
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Xiaodong Xu, D Nowell, Stephen R. Hallett
    Abstract:

    Abstract Composite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and Residual Tensile Strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the Residual Strength of impacted laminates was determined through quasi-static Tensile tests. The Residual Strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of Residual Strength.

Hui Mei - One of the best experts on this subject based on the ideXlab platform.

  • The effect of hole defects on the oxidation behaviour of two-dimensional C/SiC composites
    Ceramics International, 2016
    Co-Authors: Hui Mei, Ding Zhang, Junchao Xia, Laifei Cheng
    Abstract:

    Abstract Oxidation behaviour of two-dimensional (2D) C/SiC composites with 0, 1 and 2 mm average diameter holes has been investigated in air at 700 °C. Oxidation tests, mechanical tests, microstructural characterization and computed tomography (CT) were performed to find the effect of hole defects on the oxidation behaviour of C/SiC composites. The experimental results pointed out that the thermal exposure area (TEA) ratio and oxidation time were two key affecting factors on the oxidation behaviour. Weight loss was found to accelerate at oxidation durations higher than 1 h, thereafter Residual Tensile Strength also dropped. A TEA ratio of 16% was found as critical in severely downgrading the Residual Tensile Strength and significantly weakening the oxidation resistance behaviour for C/SiC composites contain hole defects.

  • The effects of stitched density on low-velocity impact damage of cross-woven carbon fiber reinforced silicon carbide composites
    Ceramics International, 2016
    Co-Authors: Hui Mei, Laifei Cheng
    Abstract:

    Abstract Two dimensional carbon fiber reinforced silicon carbide composites (2D C/SiCs) subjected to low-velocity impact (LVI) damage were investigated, in order to evaluate the efficiency of stitching as a reinforcing mechanism able to improve the delamination resistance of 2D C/SiCs. The damage microstructures of the specimens at different stitched density (SD) were observed by infrared thermography and industrial computed tomography scanners. While the damage depth of specimens with the SD of 10 mm/needle was greater than that of specimens with SD of 5 or 15 mm/needle, the Residual Tensile Strength of the specimens with the SD of 10 mm/needle was the highest. With the decreasing of SD, the real damage radius of 2D C/SiCs measured by thermography increased whereas the Residual Tensile Strength did not appear the same phenomenon. The 2D C/SiCs with the SD of 5, 10, and 15 mm/needle had good damage resistance after the LVI, with the Tensile Strength still retaining 72.43%, 95.20%, and 91.49%, respectively.

  • Mechanical and microstructural evolution of Hi-Nicalon Trade Mark SiC fibers annealed in O2–H2O–Ar atmospheres
    Materials Science and Engineering: A, 2008
    Co-Authors: Zude Feng, Hui Mei, Litong Zhang
    Abstract:

    Hi-Nicalon fibers were exposed in 8% O-2/78% Ar/14% H2O atmosphere for 1 h at 1300, 1400, 1500, 1600 degrees C, respectively. Residual Tensile Strength was evaluated by Tensile test, phases in the fibers were identified using an X-ray diffractometer (XRD), morphology of the fracture surfaces and microstructure was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Results indicated that Residual Tensile Strength increased with increasing temperature from 1300 to 1500 degrees C, then decreased after annealing in 1600 degrees C. The grain size of beta-SiC and the amount of the stacking faults increased under the elevated temperature as well. After annealing, a passive film with a structure of alpha-cristobalite crystals dispersed in amorphous SiO2 phase formed on the fiber surface, the thickness of the film increased with the annealing temperature from 1300 to 1500 degrees C, after annealing in 1600 degrees C, fractional silica film spalled. Finally, relationship between the structural changes and the mechanical properties, the control effect of water vapor on formation and structural evolution of the passive film were discussed. (c) 2007 Elsevier B.V. All rights reserved

  • Mechanical and microstructural evolution of Hi-Nicalon Trade Mark SiC fibers annealed in O2–H2O–Ar atmospheres
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2007
    Co-Authors: Zude Feng, Hui Mei, Litong Zhang
    Abstract:

    Abstract Hi-Nicalon fibers were exposed in 8% O2/78% Ar/14% H2O atmosphere for 1 h at 1300, 1400, 1500, 1600 °C, respectively. Residual Tensile Strength was evaluated by Tensile test, phases in the fibers were identified using an X-ray diffractometer (XRD), morphology of the fracture surfaces and microstructure was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Results indicated that Residual Tensile Strength increased with increasing temperature from 1300 to 1500 °C, then decreased after annealing in 1600 °C. The grain size of β-SiC and the amount of the stacking faults increased under the elevated temperature as well. After annealing, a passive film with a structure of α-cristobalite crystals dispersed in amorphous SiO2 phase formed on the fiber surface, the thickness of the film increased with the annealing temperature from 1300 to 1500 °C, after annealing in 1600 °C, fractional silica film spalled. Finally, relationship between the structural changes and the mechanical properties, the control effect of water vapor on formation and structural evolution of the passive film were discussed.

Ashwin R. Kristnama - One of the best experts on this subject based on the ideXlab platform.

  • numerical analysis of high velocity oblique impacts and Residual Tensile Strength of carbon epoxy laminates
    Composite Structures, 2021
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Stephen R. Hallett
    Abstract:

    Abstract This paper presents prediction of the high velocity, oblique impact response and quasi-static Residual Tensile Strength of thin [45/90/−45/0]2s carbon/epoxy laminates using finite element (FE) models. A High-Fidelity Finite Element Method (Hi-FEM) with an automated unit cell meshing technique was employed. The predicted impact damage, characterised by the extent of fibre failure and delamination area, was validated against results from gas-gun tests for a range of impact velocities. The numerical results captured the trend of increasing impact damage with impact energy as observed from the tests. Changes in projectile orientation before impact were shown to increase the extent of fibre failure at high impact energies, up by 38% in edge impact cases. The Residual Tensile Strength of the impacted laminates was then investigated, where the numerical results for edge-impacted laminates agreed with the test data within 8%. On the other hand, the Residual Strength modelling results of centre-impacted laminates were found to be unconservative, mainly due to the extent of fibre failure predicted during impact. Machined notches were also studied for their Residual Tensile Strength in comparison to impact induced damage. The predicted Strength of edge-notched laminates was found to be in close agreement with the experimental results for edge-impacted laminates, differing by an average of 9%.

  • Numerical analysis of high velocity, oblique impacts and Residual Tensile Strength of carbon/epoxy laminates
    Composite Structures, 2021
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Stephen R. Hallett
    Abstract:

    Abstract This paper presents prediction of the high velocity, oblique impact response and quasi-static Residual Tensile Strength of thin [45/90/−45/0]2s carbon/epoxy laminates using finite element (FE) models. A High-Fidelity Finite Element Method (Hi-FEM) with an automated unit cell meshing technique was employed. The predicted impact damage, characterised by the extent of fibre failure and delamination area, was validated against results from gas-gun tests for a range of impact velocities. The numerical results captured the trend of increasing impact damage with impact energy as observed from the tests. Changes in projectile orientation before impact were shown to increase the extent of fibre failure at high impact energies, up by 38% in edge impact cases. The Residual Tensile Strength of the impacted laminates was then investigated, where the numerical results for edge-impacted laminates agreed with the test data within 8%. On the other hand, the Residual Strength modelling results of centre-impacted laminates were found to be unconservative, mainly due to the extent of fibre failure predicted during impact. Machined notches were also studied for their Residual Tensile Strength in comparison to impact induced damage. The predicted Strength of edge-notched laminates was found to be in close agreement with the experimental results for edge-impacted laminates, differing by an average of 9%.

  • experimental investigation of high velocity oblique impact and Residual Tensile Strength of carbon epoxy laminates
    Composites Science and Technology, 2019
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Xiaodong Xu, D Nowell, Stephen R. Hallett
    Abstract:

    Abstract Composite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and Residual Tensile Strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the Residual Strength of impacted laminates was determined through quasi-static Tensile tests. The Residual Strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of Residual Strength.

  • Experimental investigation of high velocity oblique impact and Residual Tensile Strength of carbon/epoxy laminates
    Composites Science and Technology, 2019
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Xiaodong Xu, D Nowell, Stephen R. Hallett
    Abstract:

    Abstract Composite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and Residual Tensile Strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the Residual Strength of impacted laminates was determined through quasi-static Tensile tests. The Residual Strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of Residual Strength.

Dorys C. González - One of the best experts on this subject based on the ideXlab platform.

  • computed tomography scanning of the internal microstructure crack mechanisms and structural behavior of fiber reinforced concrete under static and cyclic bending tests
    International Journal of Fatigue, 2019
    Co-Authors: Dorys C. González, Miguel A. Vicente, Jesus Minguez
    Abstract:

    Abstract Fiber-reinforced concrete (FRC), its behavior, and the effects of cyclic loading on its internal microstructure are studied in this paper. Particular attention is given to the evolution of the Residual Tensile Strength of the fiber-reinforced concretes and damage following cyclic flexural loading. A numerical equation is also proposed to estimate the Residual Tensile Strength, depending on crack width, damage, fiber content, and fiber orientation. A total of 65 prismatic specimens, in two different series, were tested: one designed with 1% of fibers by volume and the other with 2% of fibers. The specimens were not notched, but had previously been subjected to pre-cracking, which has a similar effect to notching, although the specimens become more vulnerable to fatigue. Both fiber content and fiber orientation were measured using computed tomography (CT) scans. The results showed that the damage provoked a progressive reduction in the Residual Tensile Strength. The differences in the behavior of both series were mainly related to their fiber content and, to a lesser extent, to their fiber orientation.

  • Study of the effect of the fibers’ orientation on the post-cracking behavior of steel fiber reinforced concrete from wedge-splitting tests and computed tomography scanning
    Construction and Building Materials, 2018
    Co-Authors: Dorys C. González, Miguel A. Vicente, Jesus Minguez, Francisco Cambronero, Guillermo Aragón
    Abstract:

    Abstract The correlations between fiber orientation and Residual Tensile Strength and fracture energy in steel-fiber-reinforced concrete are analyzed with Computed Tomography (CT) Scanning, Digital Image Processing (DIP) software, and the Wedge Splitting Test (WST). A mixture containing 2% by volume of steel fibers was performed to cast a total of six prisms measuring 150 × 150 × 600 mm. Then, two cubes with 150 mm edges and a mini-prism measuring 50 × 50 × 150 mm were cut from each prism. The two cubes were subsequently prepared for the WST by sawing a groove and a notch on one face. The groove and the notch were sawn on the front face of one cube and on the side face of the other cube from each prism. All the specimens were held in a curing room at 20 °C and at 100% humidity. The mini-prisms were scanned using a micro CT-Scan and their fiber orientation obtained with DIP software. Additionally, all the cubes were subjected to the WST and the Residual Tensile Strength and fracture energy were obtained. A comparison of the results from both the CT-Scan and the WST revealed strong correlations between fiber orientation, on the one hand, and the values of both Residual Tensile Strength and fracture energy, on the other hand. Finally, a set of empirical formulas are proposed on the basis of the results.

  • effect of cyclic loading on the Residual Tensile Strength of steel fiber reinforced high Strength concrete
    Journal of Materials in Civil Engineering, 2015
    Co-Authors: Dorys C. González, Miguel A. Vicente, Shuaib H. Ahmad
    Abstract:

    AbstractThis paper evaluates variations in the Residual Tensile Strength of prismatic specimens made of steel fiber–reinforced high-Strength concrete (SFRHSC) attributable to flexural cyclic loading. All specimens were previously subjected to a three-point static bending load test until the first flexural crack appeared. In these cases, no notched specimens were used. Next, the specimens were subjected to a preset number of three-point cyclic bending loads, without fatigue failure in any case. Finally, the specimens were submitted to a three-point static load test until failure. This test procedure shows a progressive decrease in the Residual Tensile Strength with the number of cycles. A new definition of damage is introduced: relative variation of the Tensile Strength with the number of cycles. A correlation is identified between conventional damage and this new definition of damage.

  • Effect of Cyclic Loading on the Residual Tensile Strength of Steel Fiber–Reinforced High-Strength Concrete
    Journal of Materials in Civil Engineering, 2015
    Co-Authors: Dorys C. González, Miguel A. Vicente, Shuaib H. Ahmad
    Abstract:

    AbstractThis paper evaluates variations in the Residual Tensile Strength of prismatic specimens made of steel fiber–reinforced high-Strength concrete (SFRHSC) attributable to flexural cyclic loading. All specimens were previously subjected to a three-point static bending load test until the first flexural crack appeared. In these cases, no notched specimens were used. Next, the specimens were subjected to a preset number of three-point cyclic bending loads, without fatigue failure in any case. Finally, the specimens were submitted to a three-point static load test until failure. This test procedure shows a progressive decrease in the Residual Tensile Strength with the number of cycles. A new definition of damage is introduced: relative variation of the Tensile Strength with the number of cycles. A correlation is identified between conventional damage and this new definition of damage.

Michael R Wisnom - One of the best experts on this subject based on the ideXlab platform.

  • numerical analysis of high velocity oblique impacts and Residual Tensile Strength of carbon epoxy laminates
    Composite Structures, 2021
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Stephen R. Hallett
    Abstract:

    Abstract This paper presents prediction of the high velocity, oblique impact response and quasi-static Residual Tensile Strength of thin [45/90/−45/0]2s carbon/epoxy laminates using finite element (FE) models. A High-Fidelity Finite Element Method (Hi-FEM) with an automated unit cell meshing technique was employed. The predicted impact damage, characterised by the extent of fibre failure and delamination area, was validated against results from gas-gun tests for a range of impact velocities. The numerical results captured the trend of increasing impact damage with impact energy as observed from the tests. Changes in projectile orientation before impact were shown to increase the extent of fibre failure at high impact energies, up by 38% in edge impact cases. The Residual Tensile Strength of the impacted laminates was then investigated, where the numerical results for edge-impacted laminates agreed with the test data within 8%. On the other hand, the Residual Strength modelling results of centre-impacted laminates were found to be unconservative, mainly due to the extent of fibre failure predicted during impact. Machined notches were also studied for their Residual Tensile Strength in comparison to impact induced damage. The predicted Strength of edge-notched laminates was found to be in close agreement with the experimental results for edge-impacted laminates, differing by an average of 9%.

  • Numerical analysis of high velocity, oblique impacts and Residual Tensile Strength of carbon/epoxy laminates
    Composite Structures, 2021
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Stephen R. Hallett
    Abstract:

    Abstract This paper presents prediction of the high velocity, oblique impact response and quasi-static Residual Tensile Strength of thin [45/90/−45/0]2s carbon/epoxy laminates using finite element (FE) models. A High-Fidelity Finite Element Method (Hi-FEM) with an automated unit cell meshing technique was employed. The predicted impact damage, characterised by the extent of fibre failure and delamination area, was validated against results from gas-gun tests for a range of impact velocities. The numerical results captured the trend of increasing impact damage with impact energy as observed from the tests. Changes in projectile orientation before impact were shown to increase the extent of fibre failure at high impact energies, up by 38% in edge impact cases. The Residual Tensile Strength of the impacted laminates was then investigated, where the numerical results for edge-impacted laminates agreed with the test data within 8%. On the other hand, the Residual Strength modelling results of centre-impacted laminates were found to be unconservative, mainly due to the extent of fibre failure predicted during impact. Machined notches were also studied for their Residual Tensile Strength in comparison to impact induced damage. The predicted Strength of edge-notched laminates was found to be in close agreement with the experimental results for edge-impacted laminates, differing by an average of 9%.

  • experimental investigation of high velocity oblique impact and Residual Tensile Strength of carbon epoxy laminates
    Composites Science and Technology, 2019
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Xiaodong Xu, D Nowell, Stephen R. Hallett
    Abstract:

    Abstract Composite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and Residual Tensile Strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the Residual Strength of impacted laminates was determined through quasi-static Tensile tests. The Residual Strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of Residual Strength.

  • Experimental investigation of high velocity oblique impact and Residual Tensile Strength of carbon/epoxy laminates
    Composites Science and Technology, 2019
    Co-Authors: Ashwin R. Kristnama, Michael R Wisnom, Xiaodong Xu, D Nowell, Stephen R. Hallett
    Abstract:

    Abstract Composite components are required to be resilient against Foreign Object Damage (FOD) induced by localised high velocity impact events. Here an experimental investigation into high velocity oblique impacts and Residual Tensile Strength of thin quasi-isotropic carbon/epoxy laminates is reported. Oblique (45°) impacts between 100 m/s and 350 m/s were carried out using 3 mm steel cubes on the edge and the centre of the laminates, mounted as a cantilever beam. Impact induced damage was characterised using X-ray Computed Tomography (CT) and the Residual Strength of impacted laminates was determined through quasi-static Tensile tests. The Residual Strength shows a strong dependence on the impact damage size, characterised in terms of fibre fracture width and delamination area. Machined notches were then investigated and compared to impacted laminates in terms of Residual Strength.

  • Residual Tensile Strength of Adhesively Bonded Double Lap Joints Aafter Transverse Impact
    American Society for Composites 2018, 2018
    Co-Authors: Aakash Paul, Michael R Wisnom, Takayuki Shimizu
    Abstract:

    The aim of this study was to understand the effects of transverse impact on the Residual Tensile Strength of double lap joints. The experimental results were compared to baseline cases with no impact damage. The adherend and adhesive used were the Hexcel Hexply® IM7/8552 and Hexcel Redux® 319 respectively. During impact, delamination occurred within the 0° ply at the inner adherend surface ply opposite to which the impact was applied. A significant decrease in failure load was also found from the following Residual Tensile Strength tests for the impact case compared to the pristine case. While the failure mechanisms were similar, the reduction of Residual Strength appears to be mainly due to the presence of the sharp crack as a result of the impact, the decreased effective overlap length of the specimen and the lack of intact adhesive fillets after the impact.