The Experts below are selected from a list of 16227 Experts worldwide ranked by ideXlab platform

Raymond A. Pearson - One of the best experts on this subject based on the ideXlab platform.

  • the Moisture effect on the fatigue crack growth of glass particle and fiber reinforced epoxies with strong and weak bonding conditions part 1 macroscopic fatigue crack propagation behavior
    Composites Science and Technology, 2004
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    Abstract The fatigue crack propagation behavior of glass-filled epoxy composites with three different types of reinforcements was characterized. Moreover, the underlying mechanisms operating in fatigue were identified using da/dN vs. ΔK curves according to the model proposed by other investigators. The effect of Moisture was studied. In particular, the role of adhesion promoters in fatigue crack propagation behavior was determined by treating the glass reinforcements with silane-based adhesion promoters. The fatigue crack propagation behavior with Moisture Exposure was strongly dependent on the surface treatment of the reinforcements and poor matrix–particle adhesion resulted in better fatigue crack propagation resistance. An investigation revealed that the specific toughening mechanism contributing to fatigue crack propagation behavior depended on the type of reinforcement and the surface treatment. Glass spheres treated with n-butyltrimethoxysilane exhibited crack tip shielding mechanisms involving shear yielding whereas short glass fiber treated with aminopropyltrimethoxysilane exhibited contact shielding mechanisms involving fiber bridging and wedging due to asperities generated between fracture surfaces. Interestingly, the type of adhesion promoters had a significant influence on the type of toughening mechanism observed.

  • the Moisture effect on the fatigue crack growth of glass particle and fiber reinforced epoxies with strong and weak bonding conditions part 2 a microscopic study on toughening mechanism
    Composites Science and Technology, 2004
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    The toughening mechanisms in three types of glass-filled epoxy composites subject to fatigue loading were studied by several different microscopy techniques. The observed toughening mechanisms were then related to the macroscopic fatigue crack propagation behavior. The role of matrix-reinforcement adhesion was systematically investigated. Scanning electron microscopy (SEM) and transmission optical microscopy (OM) studies revealed that toughening mechanisms such as microcracking, crack pinning, shear yielding, fiber bridging, and fiber dedonding and pull-out were dependent on the surface treatment of the reinforcements as well as the shape of reinforcements. The nature of the toughening mechanisms observed agreed with the fatigue crack propagation behavior predicted by crack tip shielding concepts. Interestingly, matrix shear yielding turned out to be the prevalent toughening mechanism in those mechanisms subjected to Moisture Exposure. In dry as-molded composites, a careful investigation involving SEM, OM, fluorescent microscopy, and atomic force microscopy (AFM) indicated that the particular micromechanisms observed were indeed microcracks, and not micro-shear bands as had been suggested by other researchers.

  • the effect of particle matrix adhesion on the mechanical behavior of glass filled epoxies part 2 a study on fracture toughness
    Polymer, 2003
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    Abstract The static fracture toughness behavior of glass filled epoxies was studied using single-edge-notched 3 point bend (SEN-3PB) tests. Three different types of glass reinforcements, large glass spheres (LGS), small glass spheres (SGS), and glass fibers (GF), were examined. The surface of each type of filler was treated to either promote or inhibit particle–matrix adhesion. The volume fraction of filler studied ranged from 10 to 30 vol%. Special attention was given to the effect of particle surface treatment and/or Moisture Exposure on fracture toughness. Interestingly, Moisture Exposure resulted in improved toughness in the case of poor adhesion at the matrix–particle interface for LGS and GF filled epoxies. Transmission optical microscopy and scanning electron microscopy were used to examine the process zone in SEN-3PB specimens. These observations along with yield stress measurements suggest that the improved toughness was due to enhanced shear yielding of the matrix due to poor adhesion at the matrix–particle interface and increased matrix ductility due to the plasticizing effect of the absorbed Moisture.

  • The effect of particle - matrix adhesion on the mechanical behavior of glass filled epoxies: Part 1. A study on yield behavior and cohesive strength
    Polymer, 2003
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    Basic properties of glass filled epoxy such as yield behavior and cohesive strength, which are important in understanding toughening mechanism, are studied using compression tests and double notch 4 point bending (DN-4PB) tests. Three different glass reinforcements, large glass spheres, small glass spheres, and glass fibers, were treated by different methods and used at different volume fractions ranging from 10 to 30 vol%. The effect of different surface treatments and Moisture Exposure on the yield behavior is studied. It was found that in all types of formulation the yield stress decreased after Moisture Exposure and that the yield stress was dependent on the surface treatment both before and after Moisture Exposure. No treatment and treatment of glass reinforcements with aminopropyltrimethoxysilane coupling agent resulted in relatively higher yield stress. Close observation of microstructure by transmission OM showed that the degree of debonding in the specimens for compression tests was quite dependent on the surface treatment after Moisture Exposure. The decrease in cohesive strength of the neat specimens were observed after Moisture Exposure.

Takafumi Kawaguchi - One of the best experts on this subject based on the ideXlab platform.

  • the Moisture effect on the fatigue crack growth of glass particle and fiber reinforced epoxies with strong and weak bonding conditions part 1 macroscopic fatigue crack propagation behavior
    Composites Science and Technology, 2004
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    Abstract The fatigue crack propagation behavior of glass-filled epoxy composites with three different types of reinforcements was characterized. Moreover, the underlying mechanisms operating in fatigue were identified using da/dN vs. ΔK curves according to the model proposed by other investigators. The effect of Moisture was studied. In particular, the role of adhesion promoters in fatigue crack propagation behavior was determined by treating the glass reinforcements with silane-based adhesion promoters. The fatigue crack propagation behavior with Moisture Exposure was strongly dependent on the surface treatment of the reinforcements and poor matrix–particle adhesion resulted in better fatigue crack propagation resistance. An investigation revealed that the specific toughening mechanism contributing to fatigue crack propagation behavior depended on the type of reinforcement and the surface treatment. Glass spheres treated with n-butyltrimethoxysilane exhibited crack tip shielding mechanisms involving shear yielding whereas short glass fiber treated with aminopropyltrimethoxysilane exhibited contact shielding mechanisms involving fiber bridging and wedging due to asperities generated between fracture surfaces. Interestingly, the type of adhesion promoters had a significant influence on the type of toughening mechanism observed.

  • the Moisture effect on the fatigue crack growth of glass particle and fiber reinforced epoxies with strong and weak bonding conditions part 2 a microscopic study on toughening mechanism
    Composites Science and Technology, 2004
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    The toughening mechanisms in three types of glass-filled epoxy composites subject to fatigue loading were studied by several different microscopy techniques. The observed toughening mechanisms were then related to the macroscopic fatigue crack propagation behavior. The role of matrix-reinforcement adhesion was systematically investigated. Scanning electron microscopy (SEM) and transmission optical microscopy (OM) studies revealed that toughening mechanisms such as microcracking, crack pinning, shear yielding, fiber bridging, and fiber dedonding and pull-out were dependent on the surface treatment of the reinforcements as well as the shape of reinforcements. The nature of the toughening mechanisms observed agreed with the fatigue crack propagation behavior predicted by crack tip shielding concepts. Interestingly, matrix shear yielding turned out to be the prevalent toughening mechanism in those mechanisms subjected to Moisture Exposure. In dry as-molded composites, a careful investigation involving SEM, OM, fluorescent microscopy, and atomic force microscopy (AFM) indicated that the particular micromechanisms observed were indeed microcracks, and not micro-shear bands as had been suggested by other researchers.

  • the effect of particle matrix adhesion on the mechanical behavior of glass filled epoxies part 2 a study on fracture toughness
    Polymer, 2003
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    Abstract The static fracture toughness behavior of glass filled epoxies was studied using single-edge-notched 3 point bend (SEN-3PB) tests. Three different types of glass reinforcements, large glass spheres (LGS), small glass spheres (SGS), and glass fibers (GF), were examined. The surface of each type of filler was treated to either promote or inhibit particle–matrix adhesion. The volume fraction of filler studied ranged from 10 to 30 vol%. Special attention was given to the effect of particle surface treatment and/or Moisture Exposure on fracture toughness. Interestingly, Moisture Exposure resulted in improved toughness in the case of poor adhesion at the matrix–particle interface for LGS and GF filled epoxies. Transmission optical microscopy and scanning electron microscopy were used to examine the process zone in SEN-3PB specimens. These observations along with yield stress measurements suggest that the improved toughness was due to enhanced shear yielding of the matrix due to poor adhesion at the matrix–particle interface and increased matrix ductility due to the plasticizing effect of the absorbed Moisture.

  • The effect of particle - matrix adhesion on the mechanical behavior of glass filled epoxies: Part 1. A study on yield behavior and cohesive strength
    Polymer, 2003
    Co-Authors: Takafumi Kawaguchi, Raymond A. Pearson
    Abstract:

    Basic properties of glass filled epoxy such as yield behavior and cohesive strength, which are important in understanding toughening mechanism, are studied using compression tests and double notch 4 point bending (DN-4PB) tests. Three different glass reinforcements, large glass spheres, small glass spheres, and glass fibers, were treated by different methods and used at different volume fractions ranging from 10 to 30 vol%. The effect of different surface treatments and Moisture Exposure on the yield behavior is studied. It was found that in all types of formulation the yield stress decreased after Moisture Exposure and that the yield stress was dependent on the surface treatment both before and after Moisture Exposure. No treatment and treatment of glass reinforcements with aminopropyltrimethoxysilane coupling agent resulted in relatively higher yield stress. Close observation of microstructure by transmission OM showed that the degree of debonding in the specimens for compression tests was quite dependent on the surface treatment after Moisture Exposure. The decrease in cohesive strength of the neat specimens were observed after Moisture Exposure.

Juan A Anta - One of the best experts on this subject based on the ideXlab platform.

  • enhancing Moisture and water resistance in perovskite solar cells by encapsulation with ultrathin plasma polymers
    ACS Applied Materials & Interfaces, 2018
    Co-Authors: Jesus Idigoras, Francisco J Aparicio, Lidia Contrerasbernal, Susana Ramosterron, Maria Alcaire, Juan R Sanchezvalencia, Ana Borras, Angel Barranco, Juan A Anta
    Abstract:

    A compromise between high power conversion efficiency and long-term stability of hybrid organic–inorganic metal halide perovskite solar cells is necessary for their outdoor photovoltaic application and commercialization. Herein, a method to improve the stability of perovskite solar cells under water and Moisture Exposure consisting of the encapsulation of the cell with an ultrathin plasma polymer is reported. The deposition of the polymer is carried out at room temperature by the remote plasma vacuum deposition of adamantane powder. This encapsulation method does not affect the photovoltaic performance of the tested devices and is virtually compatible with any device configuration independent of the chemical composition. After 30 days under ambient conditions with a relative humidity (RH) in the range of 35–60%, the absorbance of encapsulated perovskite films remains practically unaltered. The deterioration in the photovoltaic performance of the corresponding encapsulated devices also becomes significantl...

Duncan J Maitland - One of the best experts on this subject based on the ideXlab platform.

  • the effect of Moisture absorption on the physical properties of polyurethane shape memory polymer foams
    Smart Materials and Structures, 2011
    Co-Authors: Keith Hearon, Thomas S Wilson, Duncan J Maitland
    Abstract:

    The effect of Moisture absorption on the glass transition temperature (Tg) and the stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood-contacting environments, we have investigated the effects of Moisture Exposure on the physical properties of polyurethane foams. To the best of our knowledge, this study is the first to investigate the effects of Moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after Exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the Tg of the foam, with a maximum water uptake shifting the Tg from 67 to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity Exposure, the plasticization effect was reversible upon placing Moisture-saturated samples in 40% humidity environments for 24 h.

Jesus Idigoras - One of the best experts on this subject based on the ideXlab platform.

  • enhancing Moisture and water resistance in perovskite solar cells by encapsulation with ultrathin plasma polymers
    ACS Applied Materials & Interfaces, 2018
    Co-Authors: Jesus Idigoras, Francisco J Aparicio, Lidia Contrerasbernal, Susana Ramosterron, Maria Alcaire, Juan R Sanchezvalencia, Ana Borras, Angel Barranco, Juan A Anta
    Abstract:

    A compromise between high power conversion efficiency and long-term stability of hybrid organic–inorganic metal halide perovskite solar cells is necessary for their outdoor photovoltaic application and commercialization. Herein, a method to improve the stability of perovskite solar cells under water and Moisture Exposure consisting of the encapsulation of the cell with an ultrathin plasma polymer is reported. The deposition of the polymer is carried out at room temperature by the remote plasma vacuum deposition of adamantane powder. This encapsulation method does not affect the photovoltaic performance of the tested devices and is virtually compatible with any device configuration independent of the chemical composition. After 30 days under ambient conditions with a relative humidity (RH) in the range of 35–60%, the absorbance of encapsulated perovskite films remains practically unaltered. The deterioration in the photovoltaic performance of the corresponding encapsulated devices also becomes significantl...