The enormous development of computer technology in the last years has caused an increased demand for numerical investigations of industrially relevant elastomeric building components. In particular the prediction of the fatigue behaviour and a realistic life time estimation are of high interest. In order to establish a powerful damage modelling it is essential to understand the micro mechanical behaviour of rubber-like polymers.
The material behaviour of rubber-like materials can be characterised as follows. Under static loading the material exhibits strongly non-linear elasticity. Dynamic testing conditions show that the material behaviour is rate-dependent including hysteresis effects. These hysteresis effects are reinforced when the material is filled for example with carbon black. If the stress level is increased in every cycle stresssoftening known as Mullins effect becomes evident. When the specimen is overloaded damage occurs inside of the rubber-like material, the specimen collapses.
The aim of this paper is to present a new method to simulate the general Mullins effect as well as the idealised one, both can be seen as a kind of damage effects. The latter one is characterised by the fact that there is no remaining strain when the specimen is completely unloaded. First ideas of damage simulations will follow using the transfer of information from the micro to the macro level.
To simulate rubber-like material behaviour a special finite element unit cell is introduced which consists of one finite tetrahedral element and six truss elements lying on each edge of the tetrahedron. Each truss element represents the micro mechanical material behaviour of a bundle of polymer chains. By help of a random assembly of such unit cells it is possible to simulate the non-linear material behaviour of unfilled elastic rubbers.
To simulate the Mullins effect we look in more detail at the physics of rubber. During cyclic loading of a rubber specimen the chains at the micro level start to break and to reconnect. In the case of macro mechanical damage whole parts of the network structure break. The comparison with experimental data shows that the proposed method leads to satisfying agreement.