MECHANICAL TESTING

POISSON'S RATIO

Poisson's Ratio - ASTM E132 for ASTM D638, ASTM D3039, ASTM E8

Touchstone can determine Poisson’s ratio, ASTM E132, with several methods including biaxial strain gages or using a multi-axis extensometer. The extensometer has a 1.0” gage length, two sensing elements to average the axial strain, and one element to simultaneously measure lateral strain.

When force is applied to a solid in a uniaxial direction, deformation occurs in the direction of the applied force. However, it also expands or contracts laterally (depending on whether the force is tensile or compressive). For homogeneous and isotropic solids, the material remains elastic under the action of the applied force, and the lateral strain has a constant relationship to the axial strain. The constant for this, which is called Poisson’s ratio, is an intrinsic material property just like Young’modulus and Shear modulus. Poisson’ratio is used for structure design where all dimensional changes resulting from application of force need to be taken into account. For this test method, Poisson’ratio is obtained from strains resulting from uniaxial stress only.

The extensometer is attached to the sample and loaded in tension or compression through the elastic region. Using an extensometer decreases preparation and test time, reducing cost.

Poisson’s ratio can be determined at elevated temperatures using two high temperature extensometers on the same sample.

References: ASTM E 132 - Standard Test Method for Poisson's Ratio at Room Temperature; ASTM D3039 - Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials; ASTM D638 - Standard Test Method for Tensile Properties of Plastics; ASTM E8 – Standard Test Method for Tension Testing of Metallic Materials

Index of Mechanical Testing