2. Materials and methods
The primary research included two basic test sets of hard and soft materials.
The monitored thicknesses were 2, 4, 6, 8,…and 20 mm. In the second
step, different combinations of thesematerials were created. The rule was —
constant thickness of the first material and increasing one for the second.
This way, combinations were created according to Fig. 1.
Two-layer combinations of hard and soft materials with hard material
constant thickness are shown at Fig. 1.
Three-layer combination of hard and soft materials with hard material
constant thickness