Measurement of Young's Modulus for plastic bag

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Measurement of Young's Modulus for plastic bag

Elastic Modulus

An important materials property is termed the tensile elastic modulus, or Young's Modulus. This is usually given the symbol E. Loosely; the modulus is defined as the force you need to provide to elongate your material.

Measuring The Elastic Modulus

The elastic modulus is measured by pulling a sample of a material in a tensile testing machine, an instrument that measures force.

Let's define stress, denoted by the Greek letter (sigma), as the force (F) normalized by the cross-sectional area (A) of the material:

Now attach an extensometer to the sample. The extensometer measures the change in length of the sample as it is being pulled.

Let's define strain, denoted by the Greek letter (epsilon), as the change in length of the fiber normalized by the initial length.

Now, plot stress versus strain. The slope of this line will give you the elastic modulus E of the material.

So, the Young's Modulus is the gradient of the Graph of Force against Extension

This technique applies for small forces, which do not irreversibly stretch the