Table of Contents
Understanding the mechanical properties of plastics is essential for engineers involved in material selection and product design. This guide provides a step-by-step approach to calculating key properties such as tensile strength, Young’s modulus, and elongation at break.
Gather Material Data
Start by collecting the necessary data from material datasheets or testing reports. Key parameters include ultimate tensile strength, yield strength, and elongation percentage. Accurate data is crucial for reliable calculations.
Calculate Tensile Strength
The tensile strength is the maximum stress a plastic can withstand while being stretched before breaking. It is calculated using:
Stress = Force / Cross-sectional Area
Measure the force applied during testing and the original cross-sectional area of the specimen. Divide the force by the area to obtain tensile strength.
Determine Young’s Modulus
Young’s modulus indicates the stiffness of a plastic. It is calculated from the slope of the initial linear portion of the stress-strain curve:
Young’s Modulus = Stress / Strain
Use the stress and strain data from tensile tests to compute this value, which helps predict how a material deforms under load.
Calculate Elongation at Break
Elongation at break measures ductility. It is expressed as a percentage increase in length:
Elongation (%) = (Final Length – Original Length) / Original Length × 100
Record the original and final lengths from tensile testing to determine this property.
Summary
- Collect accurate material data.
- Calculate tensile strength using force and area.
- Determine Young’s modulus from stress-strain slope.
- Measure elongation at break for ductility.