Elastic properties of filled and porous epoxy composites

Ishai, O.; Cohen, Leslie J.

doi:10.1016/0020-7403(67)90053-7

Cited by 204 publications

(109 citation statements)

References 8 publications

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“…(1): where ρ 0 is the density of the non-porous material. It has been well documented that the compressive modulus of composite materials increases with increasing filler content and decreases with porosity in highly porous foam systems [8,10,22]. The Gibson and Ashby model given by Eq.…”

Section: Theoretical Modellingmentioning

confidence: 99%

“…The second approach used the Ishai-Cohen model [22] to quantify the effect of Bioglass® acting as reinforcement within the PDLLA matrix. This equation has been used elsewhere for particulate filled porous foams [10].…”

Section: Theoretical Modellingmentioning

confidence: 99%

“…This equation has been used elsewhere for particulate filled porous foams [10]. The Ishai-Cohen model equation [22] can be written as Eq. (4): where m is the ratio of glass to polymer modulus By using Eqs.…”

Section: Theoretical Modellingmentioning

confidence: 99%

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Mechanical properties of highly porous PDLLA/Bioglass® composite foams as scaffolds for bone tissue engineering

et al. 2005

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This study developed highly porous degradable composites as potential scaffolds for bone tissue engineering. These scaffolds consisted of poly-D,L-lactic acid filled with 2 and 15 vol.% of 45S5 Bioglass® particles and were produced via thermally induced solid-liquid phase separation and subsequent solvent sublimation. The scaffolds had a bimodal and anisotropic pore structure, with tubular macro-pores of ~100 µm in diameter, and with interconnected micro-pores of ~10-50 µm in diameter. Quasi-static and thermal dynamic mechanical analysis carried out in compression along with thermogravimetric analysis was used to investigate the effect of Bioglass® on the properties of the foams. Quasi-static compression testing demonstrated mechanical anisotropy concomitant with the direction of the macro-pores. An analytical modelling approach was applied, which demonstrated that the presence of Bioglass® did not significantly alter the porous architecture of these foams and reflected the mechanical anisotropy which was congruent with the scanning electron microscopy investigation. This study found that the Ishai-Cohen and Gibson-Ashby models can be combined to predict the compressive modulus of the composite foams. The modulus and density of these complex foams are related by a power-law function with an exponent between 2 and 3.

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Section: Theoretical Modellingmentioning

confidence: 99%

Section: Theoretical Modellingmentioning

confidence: 99%

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Mechanical properties of highly porous PDLLA/Bioglass® composite foams as scaffolds for bone tissue engineering

et al. 2005

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“…The homogenization stiffness predictions were compared with analytical predictions presented by Ishai and Cohen (1967) for a porous composite consisting of cubic inclusions. The analytical results were derived by applying both uniform stress and uniform displacement boundary conditions on the microstructure.…”

Section: Analytical Assessmentmentioning

confidence: 99%

“…Homogenization stiffness predictions and stiffness predictions calculated from uniform displacement and uniform traction boundary conditions (Ishai and Cohen, 1967) were compared for a porous composite with solid volume fraction between 10 and 60% ( Fig. 5).…”

Section: Analytical Assessmentmentioning

confidence: 99%

Application of homogenization theory to the study of trabecular bone mechanics

Hollister

Fyhrie

Jepsen

et al. 1991

Journal of Biomechanics

137

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Ah&act-It is generally accepted that the strength and stiffness of trabecular bone is strongly affected by trabecular microstructure. It has also been hvoothesized that stress induced adaptation of trabecular bone is affected by trabecular tissue level stress and;& strain. At this time, however, there is no generally accepted (or easily accomplished) technique for predicting the effect of microstructure on trabecular bone apparent stiffness and strength or estimating tissue level stress or strain. In this paper, a recently developed mechanics theory specifically designed to analyze microstructured materials, called the homogenization theory, is presented and applied to analyze trabecular bone mechanics. Using the homogenization theory it is possible to perform microstructural and continuum analyses separately and then combine them in a systematic manner. Stiffness predictions from two different microstructural models of trabecular bone show reasonable agreement with experimental results, depending on metaphyseal region, (R">0.5 for proximai humerus specimens, R* ~0.5 for distal femur and proximal tibia specimens). Estimates of both microstructural strain energy density (SED) and apparent SED show that there are large differences (up to 30 times) between apparent SED (as calculated by standard continuum finite element analyses) and the maximum microstructural or tissue SED. Furthermore, a strut and spherical void microstructure gave very different estimates of maximum tissue SED for the same bone volume fraction (BV/TV). The estimates from the spherical void microstructure are between 2 and 20 times greater than the strut microstructure at lo-20% W/TV INTRODUCTION Stress and strain fields in individual trabeculae are determined by both overall metaphyseal geometry and the microstructural organization of a local region of trabeculae. However, directly calculating stress and strain fields for each trabecula of a whole metaphysis is impossible with current computational technology. Current techniques for determining trabecular stress have focused on either analyzing very small regions of bone with a limited number of trabeculae, or analyzing a much larger region of bone assuming it to be a solid with apparent material properties. Neither technique provides direct information about trabecular tissue stresses and strains in an entire metaphyseal region. The homogenization theory is a recently developed method which provides a systematic way to combine stress analyses at the metaphyseal and individual trabecula level. This paper presents the initial application of homogenization theory to the study of trabecular bone mechanics.Microstructural analyses are generally used to predict apparent moduli and stress distributions within representative pieces of a given microstructure. These analyses assume that the whole microstructure within a material is constructed by repeating the representative piece analyzed. This type of analysis is quite Received infinalform 14 February 1991.

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Fracture behavior of glass bead filled epoxies: Cleaning process of glass beads

Lee

Yee

2000

J. Appl. Polym. Sci.

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Inorganic particles are commonly cleaned with solvents such as alcohols before being incorporated into thermoset polymers as fillers or tougheners, but the role of the cleaning process has never been examined. In this study, the effect of the cleaning process on the fracture behavior of particulate composites is investigated using glass bead filled epoxies as model systems. The cleaning process is shown to be a simple method to strengthen the interface between the glass beads and the epoxy matrix. Although the chemistry of the glass bead surface is unlikely to be altered by the cleaning process, submicron particles that exist on the glass bead surfaces are removed by cleaning with distilled water or ultrasonic vibration. The removal of submicron particles increases the interfacial strength between the glass beads and the matrix and changes the tensile strength of the composites. However, the modulus and fracture toughness of the composites is not significantly dependent on the cleaning process. Thus, it may be the case that debonding of the glass beads is not one of the major energy dissipating mechanisms in the fracture of glass bead filled thermoset systems.

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Elastic properties of filled and porous epoxy composites

Cited by 204 publications

References 8 publications

Mechanical properties of highly porous PDLLA/Bioglass® composite foams as scaffolds for bone tissue engineering

Mechanical properties of highly porous PDLLA/Bioglass® composite foams as scaffolds for bone tissue engineering

Application of homogenization theory to the study of trabecular bone mechanics

Fracture behavior of glass bead filled epoxies: Cleaning process of glass beads

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