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Enrique V Barrera - One of the best experts on this subject based on the ideXlab platform.

  • processing a glass fiber reinforced vinyl ester composite with nanotube enhancement of Interlaminar Shear Strength
    Composites Science and Technology, 2007
    Co-Authors: Ashraf Imam, Roger Crane, Karen Lozano, Valery N Khabashesku, Enrique V Barrera
    Abstract:

    Abstract Carbon nanotubes have been considered as a promising means of enhancing the properties of advanced composites in a range of polymer systems. Expected property enhancements include high Strength and stiffness, improved toughness, impact and through-thickness properties. Z -axis properties like Shear Strength are of special interest for laminated composite structures subjected to transverse loads. This paper reports the processing of a glass fiber reinforced vinyl ester composite with nanotube integration and examines the reinforcement potential on Interlaminar Shear Strength. Several sidewall functionalized nanotube derivatives were also prepared in order to obtain high dispersion and matrix bonding. Carbon nanotube enhanced vinyl ester/glass fiber composites were fabricated by a vacuum assisted resin transfer molding process. Overcoating the glass fiber weave with nanotubes and processing modification led to enhancement of the interface properties. A maximum of 45% increase in Shear Strength over control sample was observed on several types of nanotubes with a very small amount of nanotubes (0.015 wt%) coated in the midplane ply.

  • processing a glass fiber reinforced vinyl ester composite with nanotube enhancement of Interlaminar Shear Strength
    Composites Science and Technology, 2007
    Co-Authors: Jiang Zhu, Ashraf Imam, Roger Crane, Karen Lozano, Valery N Khabashesku, Enrique V Barrera
    Abstract:

    Abstract Carbon nanotubes have been considered as a promising means of enhancing the properties of advanced composites in a range of polymer systems. Expected property enhancements include high Strength and stiffness, improved toughness, impact and through-thickness properties. Z -axis properties like Shear Strength are of special interest for laminated composite structures subjected to transverse loads. This paper reports the processing of a glass fiber reinforced vinyl ester composite with nanotube integration and examines the reinforcement potential on Interlaminar Shear Strength. Several sidewall functionalized nanotube derivatives were also prepared in order to obtain high dispersion and matrix bonding. Carbon nanotube enhanced vinyl ester/glass fiber composites were fabricated by a vacuum assisted resin transfer molding process. Overcoating the glass fiber weave with nanotubes and processing modification led to enhancement of the interface properties. A maximum of 45% increase in Shear Strength over control sample was observed on several types of nanotubes with a very small amount of nanotubes (0.015 wt%) coated in the midplane ply.

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

  • measurement and modelling of Interlaminar Shear Strength enhancement under moderate through thickness compression
    Composites Part A-applied Science and Manufacturing, 2013
    Co-Authors: Stephen R Hallett, Michael R Wisnom
    Abstract:

    Abstract Interaction between compressive through-thickness stress and out-of-plane Shear can enhance the Shear stress at which delaminations initiate in composite materials and components. In complex loading situations this may become significant, either resulting in an under prediction of Strength if it is not taken into account or even a failure to predict the correct failure mode. This effect is investigated experimentally, analytically and numerically in this work. A symmetric version of the double-notch Shear test is proposed for direct measurement of the Interlaminar Shear Strength under moderate through-thickness compression. The test has successfully measured Shear Strength enhancement under increasing through-thickness compression. A range of failure criteria presented in the literature has been compared to the results obtained. Finally the tests have been modelled using finite element analysis. User defined interface elements which take account of the effect of compression enhancement allow the experimental results to be accurately predicted.

  • modelling the effect of cracks on Interlaminar Shear Strength
    Composites Part A-applied Science and Manufacturing, 1996
    Co-Authors: Michael R Wisnom
    Abstract:

    Short-beam Shear tests of unidirectional carbon fibre/epoxy are analysed assuming Shear deformations to be concentrated at the resin-rich interfacial layers between plies. A two-dimensional finite element model is used with linear elastic continuum elements to represent the plies, and non-linear springs to model the interfaces. This approach is shown to be satisfactory provided that there is a sufficiently large number of plies. The effect of cracks of varying length and at different positions is investigated. Linear elastic strain energy release rate analysis indicates that there is not sufficient energy for small cracks to propagate. In contrast, the non-linear interface modelling approach predicts that small cracks can have a significant effect on Interlaminar Shear Strength. Excellent correlation is obtained with experimental data, and it shown that the presence of small defects is a plausible explanation for the scatter in results commonly observed in short-beam Shear tests.

  • reduction in Interlaminar Shear Strength by discrete and distributed voids
    Composites Science and Technology, 1996
    Co-Authors: Michael R Wisnom, Tom Reynolds, Nigel Gwilliam
    Abstract:

    Discrete voids of different sizes were simulated by embedding PTFE monofilaments, tubes and strips at the mid-plane of unidirectional glass fibre and carbon-fibre/epoxy plates. Short-beam Shear tests were carried out to determine the effect of the defects on Interlaminar Shear Strength. For those specimens where failure initiated from the defect, linear elastic fracture mechanics was not able to predict the reduction in Strength. However, excellent correlation was obtained with a previous finite element analysis which used non-linear springs to model the interfaces between plies. In other specimens failure initiated above and below the defect. For these failures, the main factor appears to be the increase in stress due to the reduction in net cross-section. Failure of specimens with high levels of distributed voidage was also consistent with failure being controlled mainly by the reduction in net section. It is suggested that the commonly observed decrease in Interlaminar Shear Strength with voidage is due to a combination of the reduction of cross-sectional area due to distributed voidage and initiation of failure from larger discrete voids.

  • effect of specimen size on Interlaminar Shear Strength of unidirectional carbon fibre epoxy
    Composites Engineering, 1994
    Co-Authors: Michael R Wisnom, Michael R. Jones
    Abstract:

    Abstract A systematic study has been undertaken to investigate the effect of specimen size on the Interlaminar Shear Strength of unidirectional carbon fibre-epoxy using the three-point short-beam Shear test. By varying the test parameters such as the ratio of span to thickness and the diameter of the loading roller, it is found that a valid Interlaminar Shear failure mode can be obtained and thus the three-point short-beam Shear test can be used as a reliable method to measure the Interlaminar Shear Strength, at least on a comparitive basis. From tests on four sets of scaled specimens, a significant size effect is found in the Interlaminar Shear Strength. However, the Weibull statistical model does not satisfactorily represent the size effect. The test results indicate that the Weibull modulus increases with decreasing size, and suggest that the Strength is approaching a limiting value for small specimens.

Ashraf Imam - One of the best experts on this subject based on the ideXlab platform.

  • processing a glass fiber reinforced vinyl ester composite with nanotube enhancement of Interlaminar Shear Strength
    Composites Science and Technology, 2007
    Co-Authors: Ashraf Imam, Roger Crane, Karen Lozano, Valery N Khabashesku, Enrique V Barrera
    Abstract:

    Abstract Carbon nanotubes have been considered as a promising means of enhancing the properties of advanced composites in a range of polymer systems. Expected property enhancements include high Strength and stiffness, improved toughness, impact and through-thickness properties. Z -axis properties like Shear Strength are of special interest for laminated composite structures subjected to transverse loads. This paper reports the processing of a glass fiber reinforced vinyl ester composite with nanotube integration and examines the reinforcement potential on Interlaminar Shear Strength. Several sidewall functionalized nanotube derivatives were also prepared in order to obtain high dispersion and matrix bonding. Carbon nanotube enhanced vinyl ester/glass fiber composites were fabricated by a vacuum assisted resin transfer molding process. Overcoating the glass fiber weave with nanotubes and processing modification led to enhancement of the interface properties. A maximum of 45% increase in Shear Strength over control sample was observed on several types of nanotubes with a very small amount of nanotubes (0.015 wt%) coated in the midplane ply.

  • processing a glass fiber reinforced vinyl ester composite with nanotube enhancement of Interlaminar Shear Strength
    Composites Science and Technology, 2007
    Co-Authors: Jiang Zhu, Ashraf Imam, Roger Crane, Karen Lozano, Valery N Khabashesku, Enrique V Barrera
    Abstract:

    Abstract Carbon nanotubes have been considered as a promising means of enhancing the properties of advanced composites in a range of polymer systems. Expected property enhancements include high Strength and stiffness, improved toughness, impact and through-thickness properties. Z -axis properties like Shear Strength are of special interest for laminated composite structures subjected to transverse loads. This paper reports the processing of a glass fiber reinforced vinyl ester composite with nanotube integration and examines the reinforcement potential on Interlaminar Shear Strength. Several sidewall functionalized nanotube derivatives were also prepared in order to obtain high dispersion and matrix bonding. Carbon nanotube enhanced vinyl ester/glass fiber composites were fabricated by a vacuum assisted resin transfer molding process. Overcoating the glass fiber weave with nanotubes and processing modification led to enhancement of the interface properties. A maximum of 45% increase in Shear Strength over control sample was observed on several types of nanotubes with a very small amount of nanotubes (0.015 wt%) coated in the midplane ply.

Suresh G Advani - One of the best experts on this subject based on the ideXlab platform.

  • influence of resin properties on Interlaminar Shear Strength of glass epoxy mwnt hybrid composites
    Composites Part A-applied Science and Manufacturing, 2011
    Co-Authors: V C S Chandrasekaran, Suresh G Advani, Michael H Santare
    Abstract:

    Samples of glass fiber epoxy composites made with resin containing 0.5 wt.% multiwall carbon nanotubes (MWNTs) have shown enhanced Interlaminar Shear Strength relative to unmodified epoxy when evaluated using compression Shear test. Improvement in the Interlaminar Shear Strength (ILSS) of the composites can be due to an increase in the matrix Shear Strength or an increase in the fiber–matrix interface Strength or both. In this work, we conducted tests to assess the relative contributions of the matrix Shear properties and the glass fiber–epoxy interface to the ILSS enhancement. Samples of reinforced matrix were prepared by dispersing 0.5% MWNT by weight in epoxy. Both the reinforced resin and neat resin control samples were subjected to identical ultrasonic agitation. Shear properties of the neat epoxy film and the MWNT reinforced epoxy film were investigated using a Shear punch tests on miniature specimens (6.4 mm diameter, 0.5 mm thick). The Strength of the fiber–matrix interface for both modified and unmodified matrix was also characterized using the microdroplet test. The results show that the change in ILSS is primarily due to the contribution from the Strengthening of the fiber matrix interface and not from a change in the matrix Shear Strength.

  • Interlaminar Shear Strength of glass fiber reinforced epoxy composites enhanced with multi walled carbon nanotubes
    Composites Part A-applied Science and Manufacturing, 2008
    Co-Authors: Michael H Santare, Suresh G Advani
    Abstract:

    Abstract In this study, we examine the Interlaminar Shear Strength (ILSS) of traditional glass fiber reinforced epoxy composites enhanced by strategically injecting multi-walled carbon nanotube (MWNT)–epoxy suspensions into stationary glass fiber mats. The suspensions were prepared by combining the techniques of high-speed mechanical stirring, ultrasonic agitation and acid oxidation. Two types of process designs were introduced to fabricate the hybrid MWNT/glass/epoxy composites and their relative merits were discussed. Short beam Shear (SBS) and compression Shear tests (CST) were conducted on the manufactured components to characterize the influence of the process and the weight percentage of nanotubes on the ILSS. The results show that the introduction of MWNT into the composite increased the ILSS by up to 33%. The preferential orientation of the MWNTs in the thickness direction was found to contribute to the increase in the Interlaminar Shear properties.

Michael H Santare - One of the best experts on this subject based on the ideXlab platform.

  • influence of resin properties on Interlaminar Shear Strength of glass epoxy mwnt hybrid composites
    Composites Part A-applied Science and Manufacturing, 2011
    Co-Authors: V C S Chandrasekaran, Suresh G Advani, Michael H Santare
    Abstract:

    Samples of glass fiber epoxy composites made with resin containing 0.5 wt.% multiwall carbon nanotubes (MWNTs) have shown enhanced Interlaminar Shear Strength relative to unmodified epoxy when evaluated using compression Shear test. Improvement in the Interlaminar Shear Strength (ILSS) of the composites can be due to an increase in the matrix Shear Strength or an increase in the fiber–matrix interface Strength or both. In this work, we conducted tests to assess the relative contributions of the matrix Shear properties and the glass fiber–epoxy interface to the ILSS enhancement. Samples of reinforced matrix were prepared by dispersing 0.5% MWNT by weight in epoxy. Both the reinforced resin and neat resin control samples were subjected to identical ultrasonic agitation. Shear properties of the neat epoxy film and the MWNT reinforced epoxy film were investigated using a Shear punch tests on miniature specimens (6.4 mm diameter, 0.5 mm thick). The Strength of the fiber–matrix interface for both modified and unmodified matrix was also characterized using the microdroplet test. The results show that the change in ILSS is primarily due to the contribution from the Strengthening of the fiber matrix interface and not from a change in the matrix Shear Strength.

  • Interlaminar Shear Strength of glass fiber reinforced epoxy composites enhanced with multi walled carbon nanotubes
    Composites Part A-applied Science and Manufacturing, 2008
    Co-Authors: Michael H Santare, Suresh G Advani
    Abstract:

    Abstract In this study, we examine the Interlaminar Shear Strength (ILSS) of traditional glass fiber reinforced epoxy composites enhanced by strategically injecting multi-walled carbon nanotube (MWNT)–epoxy suspensions into stationary glass fiber mats. The suspensions were prepared by combining the techniques of high-speed mechanical stirring, ultrasonic agitation and acid oxidation. Two types of process designs were introduced to fabricate the hybrid MWNT/glass/epoxy composites and their relative merits were discussed. Short beam Shear (SBS) and compression Shear tests (CST) were conducted on the manufactured components to characterize the influence of the process and the weight percentage of nanotubes on the ILSS. The results show that the introduction of MWNT into the composite increased the ILSS by up to 33%. The preferential orientation of the MWNTs in the thickness direction was found to contribute to the increase in the Interlaminar Shear properties.