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

目前用于制造大型复合材料零件的材料沉积技术在双曲面上的沉积能力有限。纤维导向工艺，如自动胶带铺设（ATL）或自动纤维放置（AFP），无法生产具有复杂几何形状的复合材料零件，而不会产生束隙或重叠等缺陷。最小转向半径取决于胶带/拖曳宽度；因此，在设计阶段需要保持尽可能大的转向半径，这极大地限制了设计的灵活性和可制造性。布里斯托尔大学开发的新型连续牵引剪切（CTS）技术可以通过利用胶带或牵引的平面内剪切变形来控制纤维，从而消除缺陷。它最大的优点是带宽度和最小转向半径之间没有耦合。因此，即使是宽ATL级磁带也可以使用，允许高材料沉积速率。然而，对于复杂的3D铺层，这一过程需要改进，因为它仍然不能消除在双曲面上铺设时的缺陷。迄今为止，三角形树脂袋是在三维复杂铺层过程中切割单个拖曳产生的，这对复合材料的机械性能有很大的负面影响。这个博士项目的目的是推进当前的CTS技术，使制造无缺陷的3D复杂复合材料零件成为可能。为了消除当前AFP工艺中不可避免地产生的拖带间隙和重叠，将开发一种新的机制来控制拖带/胶带的几何形状，从而消除三维复杂形状生产中的几何缺陷。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，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.