ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Synthetic elastomers and elastormeric-like copolymers are now being utilized for a wide spectrum of biomaterial uses including primary structural applications such as pump bladders in artificial hearts and left ventricular assist devices (LVAD), leaflets in prosthetic heart valves, and vascular prostheses. In making fatigue lifetime measurements, as well as for predicting durability, it is essential to know the biaxial stress-deformation behavior at high strain rates (high frequencies) and at extension ratios at least as high as those encountered under performance conditions. This paper describes a technique for determining the high frequency equibiaxial stress-deformation behavior of elastomers. Measurements of material parameters are made at the high strain rates (or frequencies) at which accelerated biaxial flaw growth and fatigue experiments are performed and hence do not require correction for strain-rate dependence of material properties. Furthermore, the plastic deformation (creep) which occurs in the case of viscoelastic membranes is incorporated in the calculations; yielding the “true” values of the extension ratios. Experimental measurements were performed on urethane-based biomaterials using a tuned fluid oscillator which produces cyclic biaxial inflation of the elastomeric membranes clamped around the circumference. Up to moderately large equibiaxial deformations, the form of strain energy function derived from the Gaussian, network theory (or the first approximation to Rivlin's formulation of strain energy function) was found to adequately describe the stress-deformation data. This in turn permits accurate calculation of the tearing energy under biaxial conditions, which is a prime requisite for predicting biaxial fatigue lifetime distributions.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760241105
