The Future is Remanufacturing: Composites for Life

基于连续纤维预浸料板层压板的复合材料是一种成熟的技术-广泛用于航空工业的关键结构部件，然而，复合材料发展的未来前景现在在于提供轻质厚截面复合材料部件，旨在取代主要在汽车行业中的金属部件。高耐热性、厚截面复合材料坚韧耐用，现在可以为越来越多的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、转子衬套和发动机舱内的部件。从历史上看，整体式厚截面部件通常由铝或钢制成，并且例外地由热固性复合材料制成-但是当用于厚截面模制时，这些具有根本性的缺点。热塑性不连续纤维带提供了一个诱人的替代传统热固性塑料。基于PEEK和高性能尼龙等材料的热塑性复合材料（TPC）有可能提供一种可行的轻质铝替代品，具有上级韧性和疲劳性能-这两项都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性意味着可以快速廉价地生产零件，零件数量可达100，000个，使这类复合材料特别适合汽车工业所需的体积，同时也能够用于厚截面模塑件。埃克塞特最近开发的聚醚醚酮（PEEK）碳纤维模塑料表明，这种材料在热压时达到了~ 40 GPa的体积模量，虽然低于铝提供的~ 70 GPa，但与以前的产品相比有了显著的改进。由埃克塞特大学开创的制造方法的最新进展已经看到可实现的模量可靠地推到70 GPa以上-直接与铝相当，并且，最令人兴奋的是，通过使用预固结的电荷，利用材料在制造过程中的高粘度，可以实现受控的局部取向的技术。这项技术可以彻底改变TPC行业，允许简单地制造厚截面部件，这些部件具有以前仅在多轴ATL工艺中发现的优化设计特性。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年代出现的Boggs和SMC，这使得航空和汽车工业中高性能复合材料的受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，可能会改变目前对热固性塑料的重视，这对环境非常重要。尽管对该领域进行了广泛的研究，但回收大多数类型的热固性材料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，能够在不影响性能的情况下熔化和重新压制部件，大大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，这种特性非常适合原位修复和损伤愈合。复合材料的再制造和再成型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，即材料可以通过多次重熔和重整进行再加工的程度。未来的愿景是制造商将回收/再制造说明作为标准材料说明书的一部分。

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.