Comparing Test Methods for the Intra-ply Shear Properties of Uncured Prepreg Tapes

To achieve cost-efficient manufacturing and a high part quality in Thermoset Automated Fiber Placement (TS -AFP), knowledge about the interaction between material and process parameters is of special interest. Material properties of prepregs are well known at the cured state of the resin. However, there are no standardized test procedures for the mechanical behavior of the uncured prepreg tapes. To investigate the intra-ply shear deformation behavior of uncured unidirectional prepreg tapes, we compared several measurement procedures and conducted experiments for rheometer based tests using 8552/AS4 material. We identified a rotational parallel platens rheometer test method and a torsion bar rheometer test method to be suitable. Experiments using both methods revealed that the Torsion Bar Test has a higher repeatability and the analysis is less complex. Furthermore, first results show that changes in material properties caused by aging can be analyzed using this method. In the future, we will use the Torsion Bar Test to characterize changes in deformation behavior due to material aging as well as material modifications. By this, we will be able to provide data for the material modeling thus enabling the prediction of lay-up defects such as buckling due to steering.