The stress/strain curve

Jehbco’s pure silicone extrusions are used in a wide range of applications, from aircraft seals to sea water piping gaskets.  These applications present a wide range of operating conditions that our silicone must work under, and Jehbco works with our customers to ensure the best silicone product is chosen for your application.

In order to determine the best silicone for your application, we must be able to measure the performance of our silicone.  A range of material properties are tested to describe how our silicone will perform under different conditions.  Several of these properties are measured using a stress/strain curve.

The Stress vs Strain Curve with Jehbco Silicones The stress/strain curve is created by stretching a piece of silicone and measuring both the force required to stretch the silicone (tensile force) and how much it stretches (elongation).  The silicone is stretched until it breaks.  Since the silicone samples being stretched can be different sizes, the tensile force and elongation measurements are corrected.  Tensile force is divided by the cross sectional area of the silicone to get stress and elongation is divided by the original length of the silicone to get strain.  Stress is plotted on the y-axis and strain is plotted on the x-axis to get a stress/strain curve.   An example stress/strain curve is shown  below.

From the stress/strain curve, we can determine several important mechanical properties that tell us how the silicone behaves.  The modulus of the silicone tells us how stiff the silicone is, or how hard it is to stretch.  This is measured by calculating the slope of the first part of the stress/strain curve.  Stiff silicones will have a very steep curve, while softer silicones will have a shallower curve.

The tensile strength of the silicone is the amount of stress, or normalised force, needed to break the silicone.  This is easily read off the stress/strain curve – it is the stress at the very end of the curve, where the silicone breaks.

To ensure our product works as required, it is important that properties such as modulus and tensile strength are right for the application.  Jehbco has in-house facilities for generating stress/strain curves, to help us tailor the right product for your application.

For any help with your application please review the Jehbco website, and contact us with any questions.