The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Wesley J. Cantwell - One of the best experts on this subject based on the ideXlab platform.
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The effect of moisture and loading rate on the interfacial fracture properties of sandwich structures
Polymer Composites, 2020Co-Authors: R. J. Scudamore, Wesley J. CantwellAbstract:The skin-core interfacial fracture properties of a number of dry and moisture-conditioned sandwich structures have been investigated over a range of Crosshead Displacement rates using the three point bend sandwich (TPBS) structure. It has been shown that the interfacial fracture toughness, G C , of a crosslinked PVC system decreases rapidly with loading rate, whereas the toughness of a linear PVC remains roughly constant. In contrast, the interfacial fracture toughness of the balsa core material increased steadily with increasing Crosshead Displacement rate, an effect that was attributed to the rate dependent properties of the glass fibers in the wake of the primary crack. Prolonged seawater exposure in an aluminum honeycomb structure was found to attack the bond between the epoxy matrix and the aluminum core, facilitating crack advance along the skin-core interface. Finally, it is concluded that great care should be exercised before selecting sandwich structures for hostile marine environments.
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The effect of temperature and loading rate on the mode II interlaminar fracture properties of a carbon fiber reinforced phenolic
Polymer Composites, 2020Co-Authors: L. Berger, Wesley J. CantwellAbstract:The combined effect of varying loading rate and test temperature on the mode II Interlaminar fracture properties of a carbon fiber reinforced phenolic resin has been investigated. End notch flexure tests at room temperature have shown that this composite offers a relatively modest value of GIIcNL at non-linearity and that its interlaminar fracture toughness decreases with increasing loading rate. As the test temperature is increased, the quasistatic value of GIIcNL increases steadily and the reduction in GIIcNL with loading rate becomes less dramatic. At temperatures approaching the glass transition temperature of the phenolic matrix, the interlaminar fracture toughness of the composite begins to increase sharply with Crosshead Displacement rate. A more detailed understanding of the effect of varying the test conditions on the failure mechanisms occurring at the crack tip of these interlaminar fracture specimens has been achieved using the double end notch flexure (DENF) geometry.
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The Influence of Strain Rate on the Mode III Interlaminar Fracture of Composite Materials
Journal of Composite Materials, 2020Co-Authors: D. Pennas, Wesley J. Cantwell, Paul CompstonAbstract:The Mode III interlaminar fracture toughness, GIIIc, of composite materials based on both thermoplastic and thermosetting-matrices have been investigated using the edge crack torsion (ECT) test geometry. Tests were undertaken at room temperature and over a range of Crosshead Displacement rates to study the influence of strain rate on the interlaminar fracture properties of these materials. Further information concerning the crack tip loading conditions was obtained by undertaking a finite element analysis of the ECT specimen geometry.The experimental results show that the value of GIIIc depends on initial crack length, increasing steadily with increasing crack length for both types of material. It has been shown that the interlaminar fracture toughness of the glass fiber/epoxy-based system was superior to that offered by its thermoplastic counterpart, an effect that may be due to the fact that the glass fiber-reinforced polypropylene composite was slow-cooled from its processing temperature. The interlami...
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Temperature and loading rate effects in the mode II interlaminar fracture behavior of carbon fiber reinforced PEEK
Polymer Composites, 2020Co-Authors: L. Berger, Wesley J. CantwellAbstract:The combined effect of varying loading rate and test temperature on the mode II interlaminar fracture properties of AS4/carbon fiber reinforced PEEK has been investigated. End notch flexure tests have shown that this thermoplastic-based composite system offers a very high value of interlaminar fracture toughness at room temperature. Increasing the test temperature leads to a reduction in the mode II interlaminar fracture toughness of the composite, with the value at 150°C being approximately one half of the room temperature value. In contrast, increasing the Crosshead Displacement rate has been shown to increase the value of G IIc by up to 25%. A more detailed understanding of the effect of varying temperature and loading rate on the failure mechanisms occurring at the crack tip of these interlaminar fracture specimens has been achieved using the double end notch flexure (DENF) geometry. Here, extensive plastic flow within the crack tip region was observed in all specimens. It is believed that the rate sensitivity of G IIc reflects the rate-dependent characteristics of the thermoplastic resin.
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The Influence of Loading Rate on the Mode III Interlaminar Fracture Toughness of Composite/Steel Bi-material Systems
Journal of Composite Materials, 2009Co-Authors: D. Pennas, Wesley J. CantwellAbstract:In this article, the Mode III interlaminar fracture properties of a glass/ epoxy-steel bi-material system are investigated as a function of Crosshead Displacement rates using the edge crack torsion (ECT) test geometry. For purposes of comparison, tests were also undertaken on the plain glass/epoxy composite. For a given crack length, it has been shown that the interlaminar fracture toughness of the bi-material system was inferior to that offered by the plain composite, an effect that is attributed to the reduced toughness of the interface between the two materials. The Mode III fracture toughness of both the plain composite and the bi-material samples exhibited a crack length dependency, with the measured value of G IIIc increasing with crack length. Verification of the trends in the experimental data was achieved by conducting a finite element analysis of the ECT specimen and good agreement was achieved. Furthermore, the interlaminar fracture toughness of the plain composite remained roughly constant over the range of Crosshead Displacement rates considered here, suggesting that it does not exhibit a rate-sensitive fracture behavior. In contrast, the bi-material samples exhibited very low values of Mode III fracture toughness at impact rates, associated with extensive debonding of the steel from the composite material.
William G. Fahrenholtz - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and grain orientation evolution of zirconium diboride zirconium carbide ceramics
Journal of The European Ceramic Society, 2018Co-Authors: Andrea Dangio, Ji Zou, Jon G P Binner, Gregory E. Hilmas, William G. FahrenholtzAbstract:Abstract The effect of ZrC on the mechanical response of ZrB 2 ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB 2 . The addition of ZrC also increased fracture toughness from ∼ 3 .5 MPa m for nominally pure ZrB 2 to ∼ 4 .3 MPa m due to residual thermal stresses. The toughness was comparable with ZrB 2 up to 1600 °C, but increased to 4 .6 MPa m at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (Crosshead Displacement rate = 4.0 mm min −1 ) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC.
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Ultra‐High Temperature Mechanical Properties of a Zirconium Diboride–Zirconium Carbide Ceramic
Journal of the American Ceramic Society, 2015Co-Authors: Eric W. Neuman, Gregory E. Hilmas, William G. FahrenholtzAbstract:The mechanical properties of a ZrB2-10 vol% ZrC ceramic were measured up to 2300°C in an argon atmosphere. Dense billets of ZrB2-9.5 vol% ZrC-0.1 vol% C were produced by hot-pressing at 1900°C. The ZrB2 grain size was 4.9 μm and ZrC cluster size was 1.8 μm. Flexure strength was 695 MPa at ambient, decreasing to 300 MPa at 1600°C, increasing to 345 MPa at 1800°C and 2000°C, and then decreasing to 290 MPa at 2200°C and 2300°C. Fracture toughness was 4.8 MPa·m½ at room temperature, decreasing to 3.4 MPa·m½ at 1400°C, increasing to 4.5 MPa·m½ at 1800°C, and decreasing to 3.6 MPa·m½ at 2300°C. Elastic modulus calculated from the Crosshead Displacement was estimated to be 505 GPa at ambient, relatively unchanging to 1200°C, then decreasing linearly to 385 GPa at 1600°C, more slowly to 345 GPa at 2000°C, and then more rapidly to 260 GPa at 2300°C. Surface flaws resulting from machining damage were the critical flaw up to 1400°C. Above 1400°C, plasticity reduced the stress at the crack tip and the surface flaws experienced subcritical crack growth. Above 2000°C, microvoid coalescence ahead of the crack tip caused failure.
Andrea Dangio - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and grain orientation evolution of zirconium diboride zirconium carbide ceramics
Journal of The European Ceramic Society, 2018Co-Authors: Andrea Dangio, Ji Zou, Jon G P Binner, Gregory E. Hilmas, William G. FahrenholtzAbstract:Abstract The effect of ZrC on the mechanical response of ZrB 2 ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB 2 . The addition of ZrC also increased fracture toughness from ∼ 3 .5 MPa m for nominally pure ZrB 2 to ∼ 4 .3 MPa m due to residual thermal stresses. The toughness was comparable with ZrB 2 up to 1600 °C, but increased to 4 .6 MPa m at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (Crosshead Displacement rate = 4.0 mm min −1 ) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC.
G.f. Smith - One of the best experts on this subject based on the ideXlab platform.
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Strain rate effects on the shear properties of a highly orientated thermoplastic composite material using a contacting Displacement measurement methodology – Part B: Damage evolution
Composites Science and Technology, 2020Co-Authors: N. Papadakis, Neil Reynolds, M. Pharaoh, Paul Wood, G.f. SmithAbstract:This paper is concerned with the characterisation of the shear mechanical properties of glass-fibre-reinforced thermoplastic composite laminates over a range of strain rates. The research was carried out as part of the DTI/EPSRC-funded CRACTAC programme, which was part of the FASMAT Foresight Vehicle suite of projects. Twenty-two [±45]2s laid-up specimens each were tested at 5, 50 and 500 (mm/min) Crosshead Displacement rates, using a universal testing machine. The longitudinal and transverse strains were obtained experimentally using contacting extensometry apparatus and then transformed to the ply axis using Classical Laminate Theory. A rigourous statistical treatment method was proposed for the processing and analysis of the raw data. The shear modulus decreased for increasing strain rate. The shear failure stress increased for increasing strain rate. Semi-empirical linear functions of the shear modulus and shear failure strength were proposed with respect to the logarithm of the shear strain rate. The shear failure strain was independent of strain rate. Finally, the observed opposing trends of in-plane shear modulus and shear failure stress suggested that shear damage evolution is strain rate dependent for the examined material.
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Strain rate dependency of the shear properties of a highly oriented thermoplastic composite material using a contacting Displacement measurement methodology—Part B: shear damage evolution
Composites Science and Technology, 2004Co-Authors: N. Papadakis, Neil Reynolds, M. Pharaoh, Paul Wood, G.f. SmithAbstract:Abstract This paper is the second part of a two-part series on the strain rate dependency of the shear properties of a glass/polypropylene composite laminate material. In this study the Ladeveze composite material model is used to characterise the shear damage evolution for Crosshead Displacement rates varying over three orders of mag-nitude. The research was carried out as part of the DTI/EPSRC-funded CRACTAC programme, which was part of the FASMAT Foresight Vehicle suite of projects. 22 [±45]2s laid-up specimens are each tested at Crosshead Displacement rates of either 5, 50 or 500 [mm/min], using a universal testing machine. The experimental longitu-dinal and transverse strains were obtained using contacting extensometry, and then the stresses and strains were transformed to the fibre axis using Classical Laminate Theory. The damage evolution of the shear properties is found to be strain rate dependent. The critical shear damage limit (an inversely proportional measure of the rate of the degradation of shear modulus) increases for increasing strain rate. The elementary shear damage limit (proportional to the energy required for failure) increased for increased strain rate. The onset of shear modulus degradation (measured as the shear damage energy release rate) increased for increasing strain rate. Finally, the initial shear damage limit was found to be an inappropriate measure of the onset of shear modulus degradation within this thermoplastic composite system.
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Strain rate effects on the shear mechanical properties of a highly oriented thermoplastic composite material using a contacting Displacement measurement methodology–Part A: elasticity and shear strength
Composites Science and Technology, 2004Co-Authors: N. Papadakis, Neil Reynolds, M. Pharaoh, Paul Wood, G.f. SmithAbstract:This paper is concerned with the characterisation of the shear mechanical properties of glass-fibre-reinforced thermoplastic composite laminates over a range of strain rates. The research was carried out as part of the DTI/EPSRC-funded CRACTAC programme, which was part of the FASMAT Foresight Vehicle suite of projects. Twenty-two [±45]2s laid-up specimens each were tested at 5, 50 and 500 (mm/min) Crosshead Displacement rates, using a universal testing machine. The longitudinal and transverse strains were obtained experimentally using contacting extensometry apparatus and then transformed to the ply axis using Classical Laminate Theory. A rigourous statistical treatment method was proposed for the processing and analysis of the raw data. The shear modulus decreased for increasing strain rate. The shear failure stress increased for increasing strain rate. Semi-empirical linear functions of the shear modulus and shear failure strength were proposed with respect to the logarithm of the shear strain rate. The shear failure strain was independent of strain rate. Finally, the observed opposing trends of in-plane shear modulus and shear failure stress suggested that shear damage evolution is strain rate dependent for the examined material.
Gregory E. Hilmas - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and grain orientation evolution of zirconium diboride zirconium carbide ceramics
Journal of The European Ceramic Society, 2018Co-Authors: Andrea Dangio, Ji Zou, Jon G P Binner, Gregory E. Hilmas, William G. FahrenholtzAbstract:Abstract The effect of ZrC on the mechanical response of ZrB 2 ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB 2 . The addition of ZrC also increased fracture toughness from ∼ 3 .5 MPa m for nominally pure ZrB 2 to ∼ 4 .3 MPa m due to residual thermal stresses. The toughness was comparable with ZrB 2 up to 1600 °C, but increased to 4 .6 MPa m at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (Crosshead Displacement rate = 4.0 mm min −1 ) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC.
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Ultra‐High Temperature Mechanical Properties of a Zirconium Diboride–Zirconium Carbide Ceramic
Journal of the American Ceramic Society, 2015Co-Authors: Eric W. Neuman, Gregory E. Hilmas, William G. FahrenholtzAbstract:The mechanical properties of a ZrB2-10 vol% ZrC ceramic were measured up to 2300°C in an argon atmosphere. Dense billets of ZrB2-9.5 vol% ZrC-0.1 vol% C were produced by hot-pressing at 1900°C. The ZrB2 grain size was 4.9 μm and ZrC cluster size was 1.8 μm. Flexure strength was 695 MPa at ambient, decreasing to 300 MPa at 1600°C, increasing to 345 MPa at 1800°C and 2000°C, and then decreasing to 290 MPa at 2200°C and 2300°C. Fracture toughness was 4.8 MPa·m½ at room temperature, decreasing to 3.4 MPa·m½ at 1400°C, increasing to 4.5 MPa·m½ at 1800°C, and decreasing to 3.6 MPa·m½ at 2300°C. Elastic modulus calculated from the Crosshead Displacement was estimated to be 505 GPa at ambient, relatively unchanging to 1200°C, then decreasing linearly to 385 GPa at 1600°C, more slowly to 345 GPa at 2000°C, and then more rapidly to 260 GPa at 2300°C. Surface flaws resulting from machining damage were the critical flaw up to 1400°C. Above 1400°C, plasticity reduced the stress at the crack tip and the surface flaws experienced subcritical crack growth. Above 2000°C, microvoid coalescence ahead of the crack tip caused failure.