Development of a High Precision Method to Characterize Poisson’s Ratios of Encapsulant Gels Using a Flat Disk Configuration

摘要

A high precision test method based on the compression of thin elastomeric disks was developed and implemented in order to measure Poisson’s ratios of a silicone gel and organic gel. Test fixtures consisted of a thin disk of the elastomeric gel cast between two rigid platens with the lower platen containing a centrally installed pressure sensor. A compressive load was applied to the upper glass plate and the resulting stress through the deformed disk was measured using the attached pressure sensor. Poisson’s ratios of the gels were easily determined from the thin disk’s aspect ratio and the ratio of the measured stress from the pressure sensor to the applied compressive stress. The high degree of precision for this technique is indicated by the measured Poisson’s ratios for both materials which were obtained to at least the third significant digit. Additionally, an increase in the precision of this method was observed for lower aspect ratios of the cured disks, specifically the thickness to radius. An alternative high precision cylindrical experimental technique was implemented in this study to compare the resulting Poisson’s ratio measurements to this flat disk method. This method utilized a hollow steel cylinder fitted with matching pairs of pressure sensors located at the top and bottom. Comparable results were found between the two methods for the investigated silicone gel system.