Cure Terms Glossary
The modulus of a material is a measure of its stiffness, and the dynamic modulus is the stiffness under free or forced vibration. Modulus is the ratio of stress to strain, and for materials in oscillation, stress and strain are not necessarily in phase. Under sinusoidal oscillation, the measured modulus can be resolved into in-phase and (90°) out-of phase components as shown in the figure (for shear modulus) below.
The terms storage
and loss refer to the consevation or otherwise of mechanical energy -
i.e. G' reflects the (perfectly elastic) component
where mechanical energy is conserved and G" reflects the (purely
viscous) component where mechanical energy is lost to friction heating.
A material with elements of both viscous and
elastic character is termed viscoelastic.
The storage and loss moduli can also be represented in complex notation
as G* = G' + iG".