Stiffness

The stiffness of a plastic part describes the relationship between the load acting on the part and the resulting deflection or deformation. Simply put, it indicates how strongly a plastic part resists an applied force before it deforms.

A decisive factor for stiffness is the modulus of elasticity, often also called the E-modulus. The E-modulus is a measure of material stiffness and can be derived from the stress-strain curve of a material. This curve is produced when the material is stretched under controlled conditions and the resulting stress (force per area) is plotted against the resulting strain (elongation relative to the original length).

A higher E-modulus means that the material yields less and deforms less when a certain load is applied, which indicates higher stiffness.