Spreading of carbon fiber/thermoplastic pre-preg tapes

There is always a desire to manufacture structures for the aviation sector that are stronger, lighter and cheaper than their predecessors. Laser-Assisted Automatic Tape Placement (LATP) is a process that has the potential to produce highly repeatable and accurate components more cheaply than those manufactured using autoclave processing. LATP also has the benefit of being able to process complex layers with spatially variable stiffness or Variable Angle Tow (VAT). VAT creates an advanced tailoring option that can modify load paths within a laminate, resulting in more favorable stress distributions and improved laminate performance, without increasing weight. A disadvantage of VAT is the presence of overlaps and gaps between consecutive tapes, which can cause stress concentrations and geometric tolerance issues. In-situ spreading of pre-impregnated composite tapes to fill gaps between steered tapes can eliminate these defects. Spreading also gives an additional design variable, making it possible to tailor thickness without ply drops. It would also be beneficial in manufacturing doubly curved surfaces, such as radomes, where the width at the equator is wider than at the pole. This work examines the possibility of spreading carbon fiber/PEEK pre-preg tapes. Prototype tests show that spreading of carbon fiber/PEEK tapes is possible by up to 62 %. Initial characterization tests revealed that the spreading process does not adversely affect the quality of carbon fiber/PEEK, however is capable of increasing the crystallinity of carbon fiber/PEEK tapes.