Elastomer
Properties - Bulk Modulus/Resiliency
Elastomers are often treated as incompressible
materials for analytical convience. However, in many instances the compressive
response of elastomers is very important.
Bulk or Static Modulus. The bulk modulus is a
property of a material which defines its resistance to volume change when
compressed. It can be expressed as:
K = p/ev
Here p is the hydrostatic pressure, ev is the
volumetric strain and K is the bulk modulus. In practice, a positive
volumetric strain is defined as a decrease in volume.
Measuring a material’s strain response to an
applied pressure is a simple test for bulk modulus. The bulk modulus can be
expressed as the derivative (slope) of the pressure-strain curve.
Relationships between Young’s modulus E, the
shear modulus G, and Poisson’s ratio v are related by:
- E = 3 K (1 – 2v)
- E = 2 G (1 + v)
Test Methods:
Rebound Resilience. When a pendulum hammer
impacts a rubber specimen from a certain distance or angle, the degree or
distance that the pendulum does not return is an indication of the energy lost
during the deformation.
Test Methods:
-
ISO 4662
-
ASTM D1054, D2632
