2. Consequences for the implementation of hardness tests

2.1 Loading and unloading mode

Due to the high elasticity of polymers, their springback after indentation makes it difficult to measure the size of residual indentations by optical observation. Instead of spherical indenters, pyramidal indenters are used, which impose higher deformations and thus minimize the effect of this elastic return. One technique for overcoming this difficulty is to apply a fine metal coating to the polymer surface and observe the metal deposit on the indentor. Of course, this is more of a laboratory technique than a workshop one. As the behavior of polymers is time-dependent, it is also important to control the force application time.

The difficulty of applying "traditional" hardness techniques explains the interest in applying instrumented...