In several fields of engineering the use of carbon fibre reinforced material (CFRP) is increasing. Minimized weight due to CFRPs could lead to lower consumption of raw materials especially in the automotive area. The goal within the research project TC² is the decrease of costs and production time for composite materials. To achieve better performance to weight ratio and to get acceptable production conditions the draping of dry unidirectional textiles and a following RTM process is investigated. Due to the high degree of complexity of automotive structures the forming process is challenging. Gapping in the textile could appear at corners as well as wrinkling or flexion of the fibres. To be able to define the amount and direction of layers or patches it is necessary to know the limits of forming for unidirectional material and to be able to predict the behaviour of the textile during the forming process. For the definition of the process limits several draping strategies are performed on different corner blend geometries. The goal of that work is to define the critical gradient of the flange to get first failures such as wrinkling or gapping. It is also important to understand the influence of different draping strategies. Parallel to the experimental tests a mesoscopic simulation method using an approach with roving and sewing thread is developed and presented. It is able to predict the material behaviour in critical areas (gapping, wrinkling). Different Young’s moduli and failure criteria can be implemented for the two main directions as well as for the bending of the textile. A validation with the experimental results is performed with the aim to enable the prediction of the textile behaviour using simulation methods.
In several fields of engineering the automation of the CFRP production chain is a major issue. In this production chain the forming plays a key role, as the result of the forming influences everything in the chain from the infusion step until the part mechanics. To understand the influence of the material choice onto the forming process is a task followed by many scientists during the last 20 years. Basic tests for shear characterization like Picture Frame Test (PFT) and Bias Extension Test (BiasExt) were developed and used widely. This work deals with the comparison of the BiasExt to a fiber extraction test. The fiber extraction test is developed and used for the characterization of a woven and two non-crimp fabric material. The results are important for the process information and the judgment of primary deformation mechanisms. The tests are simulated for the unidirectional material in a mesoscopic approach and the results are compared in order to judge the capability of the mesoscopic simulation and its residual limitations.
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