Comparison of fibre angles between hand draped carbon fibres and draping simulation

Abstract

The mechanical properties of carbon fibre reinforced plastics, short CFRP, are highly sensitive to its respective fibre angles. Small deviations result in a high decrease of stiffness in the manufactured parts. In the first steps of industrial engineering for CFRP parts, draping simulations are used to give an approximation of fibre angles that the real draped fabrics adjust to when draped in its three dimensional state. Since the draping simulations are based on mathematical models they do not match the draping results of the manual performed production processes. In order to compensate these manufacture errors, tolerance ranges for fibre angle deviations are set very high. One way to control the fibre angle after draping is to use optical camera systems for quality assurance. The approach at DLR Augsburg to measure fibre angles is realised with a CCD camera, which is mounted on an industrial robot. The measurement system is highly sensitive regarding the reference orientation. Every deviation from the normal axis results in deviation of the measured angle. The setup with the robot guaranties high reproducibility in measurements and a high accuracy to the reference. In this paper a specified cut piece was used to perform draping simulations with different mathematical models. The cut piece was manually draped onto a tooling. The resulting fibre angles were measured with the robot controlled measurement system. In the end a comparison between the simulated and draped fibre angles was done. The result provides hints which solver delivers the lowest errors for the draped cut piece. With this information the tolerance ranges could be reduced which lead to fewer plies of carbon fibres. Less carbon fibres lead to less material cost, weight and manufacturing time.