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Maurizio Porfiri - One of the best experts on this subject based on the ideXlab platform.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

Paolo Ponzo - One of the best experts on this subject based on the ideXlab platform.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

Francesco Malanca - One of the best experts on this subject based on the ideXlab platform.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

Lorenzo Bardella - One of the best experts on this subject based on the ideXlab platform.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

  • a micromechanical model for quasi brittle compressive failure of glass microballoons thermoset matrix syntactic foams
    Journal of The European Ceramic Society, 2014
    Co-Authors: Lorenzo Bardella, Andrea Panteghini, Francesco Malanca, Paolo Ponzo, Maurizio Porfiri
    Abstract:

    Abstract We propose a micromechanical model for the quasi-brittle failure of syntactic foams subject to uniaxial compression. We focus on a failure characterised by shear bands inclined of about 45° with respect to the loading axis, often observed in thermoset polymers filled with glass microballoons. Our objective is to develop a three-dimensional Finite Element (FE) model for the effective compressive strength. Towards this aim, we extend our previous FE models, which include fifty randomly placed balloons and were developed to assess the accuracy of linear elastic homogenisation procedures for syntactic foams. Here, we account for the Filler polydispersion and introduce a novel structural failure criterion for the glass microballoons. The proposed models are shown to be macroscopically isotropic with respect to the effective strength. We find good agreement with experimental results from the literature on syntactic foams with Filler Volume Fraction of 60%, for which we assume the matrix to be linear elastic.

Hareesh V. Tippur - One of the best experts on this subject based on the ideXlab platform.

  • effect of Filler shape Volume Fraction and loading rate on dynamic fracture behavior of glass filled epoxy
    Composites Part B-engineering, 2014
    Co-Authors: Vinod Kushvaha, Hareesh V. Tippur
    Abstract:

    Abstract The effect of Filler shape and Filler Volume Fraction on the dynamic fracture behavior of particulate polymer composites (PPC) has been studied. Mode-I dynamic fracture experiments were carried out on pre-notched glass-filled epoxy. An experimental setup comprising of a gas-gun and a long-bar was used to deliver one-point impact loading to unconstrained specimens. Pulse shapers were utilized to control the loading rate during impact loading. The dynamic crack initiation and propagation events were captured using high-speed photography (∼300,000 frames per second). Digital Image Correlation (DIC) method was utilized to measure in-plane displacement fields around the crack-tip and extract fracture parameters including stress intensity factor histories to examine the Filler shape, Volume Fraction and loading rate effects. The results showed a pronounced improvement in crack initiation toughness for rod-shaped Fillers producing ∼145% increase over unfilled epoxy at 15% V f with flakes and spherical Fillers showing ∼97% and ∼67% improvement, respectively. For all three different Volume Fractions – 5%, 10%, and 15% – considered, the rod-shaped Fillers produced the highest crack initiation toughness as well as post-initiation stress intensity factors followed by flakes and spheres, respectively. A linear relationship between crack initiation toughness and log of Filler aspect ratio was also recorded. In addition, for 10% V f rod-shaped Filler case, the effect of loading rate on dynamic fracture behavior has been examined. The loading rate study showed ∼113% and ∼50% increase in crack initiation toughness for the lowest and the highest loading rate cases, respectively, compared to that of neat epoxy.

  • effect of Filler particle shape on dynamic fracture behavior of glass filled epoxy
    2013
    Co-Authors: Vinod Kushvaha, Hareesh V. Tippur
    Abstract:

    The effect of Filler shape and Filler Volume Fraction (micron sized rods, flakes and spheres) on dynamic fracture behavior of particulate polymer composites (PPC) is studied. The mode-I dynamic fracture experiments are carried out on pre-notched glass-filled epoxy specimens. An experimental set-up comprised of a long-bar apparatus to deliver one-point impact loading to an unconstrained specimen, is used in conjunction with a gas-gun. A controlled stress pulse is delivered to the specimen by impacting the long-bar by a striker launched using a gas-gun. A crack propagates into the specimen dynamically and is captured using high-speed photography (~300,000 frames per second). Using the Digital Image Correlation (DIC) method, in-plane displacement fields around the crack tip are determined from the speckle images recorded during the fracture event. With these, dynamic fracture toughness histories are evaluated to examine the Filler shape effects. The results show pronounced improvement fracture toughness for all Filler types with rod-shaped Fillers producing ~145% increase in crack initiation toughness over unfilled epoxy at 15% V f with flakes and spheres showing ~97% and ~67% improvement, respectively.

  • Evaluation of crack tip fields and stress intensity factors in functionally graded elastic materials: Cracks parallel to elastic gradient
    International Journal of Fracture, 2002
    Co-Authors: C.-e. Rousseau, Hareesh V. Tippur
    Abstract:

    Particulate functionally graded materials (FGM) made of glass-filled epoxy with edge cracks parallel to the direction of the elastic gradient and subjected to pure bending have been studied. Crack tip measurements are used to examine continuum models for FGMs by treating the material as isotropic and nonhomogeneous at macroscales. Situations where cracks are located on the compliant and the stiff sides of the beams are separately examined by mapping crack tip deformations using optical interferometry. Comparative experiments on homogeneous compositions corresponding to identical elastic properties of the crack tip region in the FGM are also undertaken. A methodology for extracting fracture parameters in FGMs based on locally homogeneous material descriptions is advanced. Companion finite element models are used to aid the development of fringe analysis procedures and to provide a direct comparison to the optical measurements. Stress intensity factors in FGMs are compared to each other and to their homogeneous counterparts. Optical measurements near quasi-statically growing cracks in FGMs have been undertaken, and crack growth resistance behavior is explained using crack initiation toughness variation as a function of Filler Volume Fraction in homogeneous sheets.

  • dynamic fracture of compositionally graded materials with cracks along the elastic gradient experiments and analysis
    Mechanics of Materials, 2001
    Co-Authors: Carlernst Rousseau, Hareesh V. Tippur
    Abstract:

    Abstract Crack tip deformation and fracture parameter histories in compositionally graded glass-filled epoxy are evaluated for low velocity impact loading. The situations when the elastic gradient is unidirectional with crack orientation along the gradient are examined. The fracture behavior of graded compositions is studied relative to homogeneous counterparts made of identical constituents. Optical method of CGS and high-speed photography are used to measure crack tip deformations prior to crack initiation and during dynamic crack growth. The apparent stress intensity factors prior to crack initiation are determined using dynamic equivalent of the stationary fields for FGMs while crack tip fields for steadily growing cracks in FGMs are used for post-initiation situations. Results from finite element simulations up to crack initiation are in excellent agreement with the experimental evaluations. Post crack initiation stress intensity factor histories and crack growth resistance behaviors for FGMs with monotonically increasing and decreasing elastic gradient are strikingly different. When the crack growth occurs into material with progressively increasing Filler Volume Fraction, continuously increasing KID(t) is seen while a decreasing trend is observed when the gradient is of the opposite sense. The fracture behaviors are explained by independent fracture tests and fractured surface micrographs.