Investigation of Alignment Methods and Its Effect on Mechanical Performance of Discontinuous Tow-based Composites

Abstract

Composites are used in applications where the combination of low density and high stiffness is wanted, as can be frequently found in the aerospace industry. Within the composites family, discontinuous fiber composites (DFC) started to gain interest in the aerospace and automotive industry, due to their potential for high production rates. In order to make these materials more appealing for real structure applications, their mechanical properties have to be improved and predicted with higher accuracy. This can be achieved by modifying the fiber orientation inside the material so properties such as stiffness and strength can be tailored for the application. The present thesis has focused on the development of different alignment methods and investigation of the effect of the alignment of discontinuous composite tapes on the material properties. The characterization of the alignment methods is performed by quantifying the level of alignment in the manufacturing process with a digital image processing tool. Based on these results, one alignment method is proposed for the manufacturing of specimens for mechanical testing. Besides this, an outlook is given for the implementation of this method into an automated process. Multiple test samples with different tape orientation distributions have been manufactured and tested in order to quantify the effect of tape alignment on the strength and modulus under tensile and shear loading. It is found that aligned DFC have an average tensile strength and stiffness of respectively 96\% and 145\% above the average values of randomly orientated DFC. This research has proved the potential of aligned DFC by showing their enhanced mechanical performance and time-efficient manufacturing cycle. It is intended that the obtained results can help make the use of DFC more appealing for academia, but also for industrial applications in the near future.