When a rubber compound is forced into intimate contact with a surface constructed from such a material as glass, concrete, or asphalt, a layer of visco-elastic material is created at the interface. The thickness of the layer at the interface is generally conceived to be at molecular scale. Its mechanical properties are different from, but are related to, those of the “parent” rubber.

In this Technical Memorandum, results from experiments on rubber hemispheres are used to construct an empirical function that is sufficient, for practical engineering purposes, to describe those mechanical properties.

The mechanical properties of the interface material, relevant to the calculation of a coefficient of decelerating force, are supposed to be limited to:

1. Elastic modulus and a reference elastic modulus,

2. Rigidity modulus and a reference rigidity modulus,

3. Poisson's ratio and

4. Phase angle (between stress and strain).

The influence of phase angle is conveniently expressed by way of an effective rebound resilience.

The force coefficient opposing the start of motion when a rubber block is pressed on to a dry surface is assumed to consist of two components: hysteresis and adhesion. For a wet surface, the adhesive component is assumed to be zero.

The effect of the condition of the surface micro-texture is accountable by means of a sharpness parameter.

The modelling scheme is valid over the range of bearing pressures likely to be encountered in practical aircraft operations.