Re­cyc­ling & Re-Use Po­ten­tiale

Modelling of the material behaviour of wood-plastic composites with a matrix of thermoplastic elastomer using stochastic-possibilistic simulation methods.

Supervisor:

1. Supervisor:                Prof. Dr. Rolf Mahnken
2. Supervisor:                N.N.
3. Practice partner:         N.N.
4. Industry partners:   N.N.

Motivation:

The resource-saving material WPC (Wood-Plastic-Composite) is a composite material that is in demand in the plastics industry and is becoming increasingly important. These are thermoplastically processable composite materials that consist of a matrix of plastic with wood fibres embedded in it. Advantages of the composite material compared to pure plastic or pure wood products include free, 3-dimensional mouldability, higher rigidity, a lower coefficient of thermal expansion, better haptic properties and improved weather resistance. The use of the composite material is therefore recommended in living areas as well as in outdoor areas.

Objective:

In the project, the statistical properties of WPC with TPE matrix, which have not been investigated so far, are to be researched and characterised using suitable simulation methods. For the application of this material, especially the strength and the damping properties are of great importance. The characterisation of the statistical properties is based on the non-homogeneously distributed wood fibres within the TPE, whose lengths and orientation are subject to uncertainty. These factors are particularly important in combination with the strongly non-linear compression and elongation properties of the TPE when describing the material behaviour.

The main research foci of the LTM are specified as follows:

1. Experimental investigation of WPC samples to statistically record the material characteristics.
2. Characterisation of the temporally and spatially changing wood fibre length distributions within the TPE matrix.
3. Investigation of the statistical composite properties of TPE-WPC in combination with different wood structures.
4. Implementation of suitable stochastic-possibilistic material models for the simulation of TPE-WPC or the composite of TPE-WPC with wood structures.

Procedure / Methods:

In many FE applications there is often uncertainty regarding the material parameters of the simulation model. This results in an uncertainty in the system response and thus in the numerical simulation. The stochastic method offers a possibility to quantify this uncertainty. Here, stochastic fields describe the uncertain system parameters. This means that the solution for a mechanical boundary value problem is done with the stochastic finite element method (SFEM). Hybrid structures are a composite of e.g. metals and prepregs (preimpregnated fibres). For metals, the number of influencing variables for uncertainties as a result of manufacturing is manageable. With prepregs, on the other hand, there are several influencing variables that are subject to a distribution. The most important are the curing of the matrix, the orientation of the fibres and the volume fractions of the fibres. When combined into a hybrid component, other factors, such as the connection of the individual components or also different coefficients of thermal expansion, then have an influence. The final properties of the composite are therefore difficult to determine with certainty from experimental data due to the abundance of boundary parameters. Therefore, the essential goal is to determine the statistical distribution of the material parameters and to take them into account in the FE simulation.