Three-point bending analyses of short fiber reinforced thermoplastics: A comparison between simulation and test results

In the context of lightweight design short fiber reinforced thermoplastics (SFRT) became increasingly popular due to their beneficial stiffness to weight ratio as well as their low fabrication costs. However, the prediction of the mechanical behaviour of parts made of SFRT by simulation is complex, because of the process induced fiber orientation. Especially in early design steps commonly imprecise isotropic simulation approaches are deployed in order to save time. In the present paper several anisotropic simulation approaches are evaluated regarding their modelling effort and accuracy.

The paper starts with a description of the fundamentals of the anisotropic simulation of SFRT structures. Basically, the anisotropic properties of the part to be analysed are determined by an injection moulding simulation, which is linked with a structural mechanical simulation. Additionally, an anisotropic simulation methodology developed by the authors is introduced (IS4ED-approach-Integrative Simulation for Early Design Steps). Within three-point-bending analyses results delivered by the IS4ED-approach as well as by several commercial simulation tools are opposed experimental results. The analysed specimens are extracted from homogenous orientated plates 0°, 45° and 90° with respect to the preferred orientation. The accuracy of the focused simulation methods and the connected modelling effort are discussed.

It can be noted, that all of the investigated simulation approaches can predict the general anisotropic behaviour of the test specimens quite well. However, the models created with the commercial tools are characterized consistently by a too stiff behaviour. The IS4ED-approach can predict the absolute displacement values more precisely. Furthermore, the FE-models created with the academic approach are significantly more compact, which makes their handling in the preprocessing more convenient.