Advanced Continuous Tow Shearing for manufacturing defect-free complex composite parts

用于制造大型复合材料部件的现有技术材料沉积技术在双曲面上的铺设能力有限。纤维转向工艺，如自动铺带（ATL）或自动纤维铺放（AFP），不能生产具有复杂几何形状的复合材料部件而不引起如丝束间隙或重叠的缺陷。最小转向半径取决于带/丝束宽度;因此，转向半径需要在设计阶段保持尽可能大，这极大地限制了设计灵活性和可制造性。布里斯托大学开发的新型连续丝束剪切（CTS）技术允许通过利用带或丝束的面内剪切变形来转向纤维来消除缺陷。它的最大优点是在磁带宽度和最小转向半径之间没有耦合。因此，即使是宽ATL级胶带也可以使用，从而实现高材料沉积速率。然而，对于复杂的3D铺层，该工艺需要改进，因为它在双曲面上铺层时仍然不能消除缺陷。迄今为止，三角形形状的树脂口袋是通过在三维复杂铺层过程中切割单个丝束而诱导的，这对复合材料的机械性能具有高度负面影响。该博士项目的目的是推进当前CTS技术，以实现无缺陷的三维复杂复合材料部件的制造。为了消除在当前AFP工艺中不可避免地产生的丝束间隙和重叠，将开发一种可以控制丝束/带的几何形状的新颖机构，其将消除在3D复杂形状的生产中的几何形状引起的缺陷。具有这种新机制的先进CTS工艺将成为当前AFP工艺质量问题的创新解决方案，并显着扩展复合材料结构的设计空间，从而实现超高的结构效率。

Current state of the art material deposition technology used to manufacture large composite parts has a limited capability in laying up on double curved surfaces. Fibre steering processes, such as automated tape laying (ATL) or automated fibre placement (AFP) are not capable of producing composite parts with complex geometry without inducing defects like tow gaps or overlaps. The minimum steering radius is dependent on the tape/tow width; Therefore, the steering radius requires to be kept as large as possible in the design phase, which significantly constrains the design flexibility and manufacturability.The novel continuous tow shearing (CTS) technology, developed at the University of Bristol, allows to eliminate defects by steering fibres utilising in-plane shear deformation of the tape or tow. Its greatest advantage is that there is no coupling between the tape width and the minimum steering radius. Hence, even wide ATL grade tapes may be used allowing high material deposition rates.However, this process requires to be improved for complex 3D layup, as it still does not eliminate defects when laying up on double curved surfaces. To date, triangular shaped resin pockets are induced by cutting individual tows during a 3-dimensional complex layup, which have a highly negative impact on the mechanical properties of the composite.The aim of this PhD project is to advance the current CTS technology to enable manufacturing of defect-free 3D complex composite parts. In order to eliminate the tow gaps and overlaps that are inevitably produced in the current AFP process, a novel mechanism that can control the geometry of the tow/tape will be developed, which will eliminate geometry induced defects in production of 3D complex shapes. The Advanced CTS process with this novel mechanism will become an innovative solution to the quality problems of the current AFP process and significantly expand the design space of composite structures, allowing for ultra-high structural efficiency.