The Future is Remanufacturing: Composites for Life

基于连续纤维预浸板层压板的复合材料是一种成熟的技术，广泛应用于航空工业的关键结构部件。然而，复合材料的未来发展方向在于提供轻量化的厚截面复合材料部件，以取代汽车行业的主要金属部件。高耐热性、厚截面、坚固耐用的复合材料现在可以为越来越多的副底盘应用提供可行的金属替代技术，特别是车轮、悬架、制动系统齿轮箱、转子护罩和发动机舱内的部件。从历史上看，整体型厚截面部件通常由铝或钢制成，并且特别使用热固性复合材料-但是当用于厚截面成型时，这些具有根本的缺点。热塑性不连续纤维带提供了一个诱人的替代传统热固性。基于PEEK和高性能尼龙的热塑性复合材料（TPC）有可能提供一种可行的轻质铝替代品，具有卓越的韧性和疲劳性能-这是汽车和航空应用的关键考虑因素。优异的可成形性和高流动特性意味着零件可以快速廉价地生产，零件数量达到10万件，使这类复合材料非常适合汽车工业所需的体积，同时也能够用于厚截面成型。埃克塞特大学最近开发的聚醚醚酮（PEEK）碳纤维模压化合物表明，这种材料在热压时的体积模量为~40GPa，虽然低于铝提供的~70GPa，但与以前的产品相比，这是一个显着的改进。由埃克塞特大学（University of Exeter）开创的制造方法的最新进展，已经将可实现的模量可靠地推至70GPa以上，与铝相当，最令人兴奋的是，一种技术可以通过使用预固结料，利用材料在制造过程中的高粘度，实现可控的局部定向。这项技术可以彻底改变TPC领域，允许简单地制造厚截面部件，具有优化的设计特性，以前只在多轴ATL工艺中发现。正在提出的新的“预充电”路线将简化制造，并消除快速批量生产的障碍，类似于20世纪70年代预浸料和SMC的出现，使航空和汽车工业中高性能复合材料的可控大规模制造成为可能。性能的基线改进以及制造障碍的消除，可能会将目前对热固性塑料的重视转变为对环境非常重要的热塑性塑料。尽管对该领域进行了广泛的研究，但大多数类型的热固性塑料的回收利用在商业上是不可行的。基于热塑性塑料的系统具有解决回收问题的潜力，具有在不影响性能的情况下熔化和再压组件的能力，极大地提高了材料的可回收性——这是热固性CFRP长期以来无法实现的特性。此外，这种特性特别适合原位修复和损伤愈合。复合材料的再制造和重塑的可行性需要建立所有最常见的TPC的可用。该研究将考虑组件的再制造（闭环回收），以及TPC的“形状变化”的可行性，即材料可以像金属一样通过多次重新熔化和重组进行再加工的程度。未来的愿景是制造商将回收/再制造说明作为标准材料数据表的一部分。

Composites based on continuous fibre prepreg sheet laminates are a mature technology - widely used in the aviation industry for key structural components, However, the future horizon for composite development now lies in providing lightweight thick-section composite parts aimed at replacing metal components predominantly within the automotive sector. High thermal tolerance, thick section composites that are tough and durable could now offer a viable metal replacement technology for an expanding range of sub-chassis applications, particularly wheels, suspension, braking systems gear casings, rotor shrouds and components within the engine compartment. Historically, monolith-type, thick-section parts have typically been made from aluminium or steel, and exceptionally with thermoset composites - but these have fundamental drawbacks when used for thick-section moulding. Thermoplastic discontinuous fibre tapes offer a tantalising alternative to traditional thermosets. Thermoplastic composites (TPC) based on e.g. PEEK and high-performance Nylons have the potential to offer a viable lightweight aluminium replacement option, with superior toughness and fatigue performance - both critical considerations for both automotive and aviation applications. The excellent formability and high flow characteristics mean parts can be produced quickly and cheaply with part counts into the 100,000's, making this class of composites uniquely suited to the volume demanded by the automotive industry, whilst also being capable of being used in thick section mouldings . The recent development of Polyether ether ketone (PEEK) carbon fibre moulding compounds at Exeter showed that this material achieves a bulk modulus of ~40GPa when hot-pressed, which, whilst short of the ~70GPa offered by aluminium, is a marked improvement over previous offerings. Recent advances in manufacturing approach pioneered by the University of Exeter have seen the achievable modulus reliably pushed above 70GPa - directly on par with Aluminium, and, most excitingly, a technique by which controlled, localised orientation might be achieved through the use of pre-consolidated charges, exploiting the high viscosity of the material during manufacture. This technique could revolutionise the TPC sector, allowing the simple manufacture of thick-section components with the optimised design properties previously found only in multiaxial ATL processes. The new "pre-charges" route being proposed, will simplify manufacture, and remove the barriers to rapid volume production, similar to the advent of prepregs and SMC in the 1970's, that made possible the controlled, mass-manufacture of high performance composites in the aviation and automotive industries. A base line improvement in properties together with the removal of manufacturing barriers, could change the current emphasis on thermosets to thermoplastics, which is highly important environmentally. Recycling of most types of thermosets is not commercially viable, despite extensive research into the area. Thermoplastic based systems have the potential to solve the recycling issue, with the ability to melt and re-press components without performance implications greatly improving the recyclability of the material - a characteristic that has long eluded thermoset CFRP's. Moreover, this trait lends itself exceptionally well to in-situ repair and damage healing. The viability of remanufacture and remoulding of composites needs to be established for all of the most common TPC's available. The study will both consider the remanufacture of components (closed loop recycling), and also the viability of 'shape change' with TPC's, i.e. the extent to which materials can be reprocessed like metals through re-melting and reforming multiple times. The future vision is for manufacturers to include recycling/remanufacture instructions as part of standard materials datasheets.