Effect of pressure on mechanical behavior of filled elastomers

Materials Science, mechanical behavior, elastomers

Yagii, Keikichi ; Tschoegl, Nicholas W.

University:California Institute of Technology

Department:Engineering and Applied Science

关键词: Materials Science, mechanical behavior, elastomers;   

Others  :  https://thesis.library.caltech.edu/8593/1/Yagii-k-1972.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The Young's modulus, stress-strain curves, and failureproperties of glass bead-filled EPDM vulcanizates were studied under superposed hydrostatic pressure. The glass bead-filled EPDM was employed as a representation of composite systems, and the hydrostatic pressure controls the filler-elastomer separation under deformation. This separation shows up as a volume change of the system, and its infuence is reflected in the mechanical behavior as a reinforcing effect of variable degree.

The strain energy stored in the composite system insimple tension was calculated by introducing a model whichis described as a cylindrical block of elastomer with twohalf spheres of filler on each end with their centers on the axis of the cylinder. In the derivation of the strain energy, assumptions were made to obtain the strain distribution in the model, and strain energy-strain relation for the elastomer was also assumed. The derivation was carried out for the case of no filler-elastomer separation and was modified to include the case of filler-elastomer separation.

The resulting strain energy, as a function of stretch ratio and volume of the system, was used to obtain stress-strain curves and volume change-strain curves of composite systems under superposed hydrostatic pressure.

Changes in the force and the lateral dimension of a ringspecimen were measured as it was stretched axially under asuperposed hydrostatic pressure in order to calculate the mechanical properties mentioned above. A tensile tester was used which is capable of sealing the whole system to carry out a measurement under pressure. A thickness measuring device, based on the Hall effect, was built for the measurement of changes in the lateraldimension of a specimen.

The theoretical and experimental results of Young'smodulus and stress-strain curves were compared and showedfairly good agreement.

The failure data were discussed in terms of failure surfaces, and it was concluded that a failure surface of the glass-bead-filled EPDM consists of two cones.