Development of novel transportation shells for use in high volume composite part manufacture: the clamshell concept

在利用直接浸渍/液体复合材料模塑技术制造复合材料部件期间，利用增粘剂（或“粘合剂”）将干燥层压材料保持成形。这使得干燥的材料成为所谓的“预成型件”。干燥材料的预成型有两个关键目的：首先，它允许预成型件在完全浸渍之前保持其形状。这有助于防止由于预成型件的处理和运输而在预成型件中产生缺陷，同时允许减小体积因数和损坏工具的可能性。其次，预成型允许更有效地利用设备;灌注设备可以仅专用于灌注/固化，而不是成型。这与传统上使用预浸料坯材料的制造技术相反，并且对于任何制造工艺向大批量、自动化装配线型工艺的升级是至关重要的。当使用粘合剂材料时，一个关键问题是粘合剂材料的“活化”和冷却的大量时间成本，占典型HP-RTM部件的时间成本的一半以上。因此，去除这些可以大大减少这些部件的节拍时间，并允许显著增加可能生产的部件的体积。此外，粘合剂材料的使用还显示出降低了布的渗透性，导致较低的浸渍，以及通过在主体结构内引入除纤维或基质之外的材料而降低了最终部件的质量。因此，可以看出，去除这些稳定剂可以导致产量的急剧增加和最终部件质量的提高。一种实现这一点的新方法是这里所阐述的工作的重点。为了实现粘合剂的去除，已经设想了一种称为“蛤壳式概念”的新概念。这个概念旨在不包括任何形式的传统粘合剂。相反，应使用预制外壳结构来保持和夹紧预成型件。这将允许将预成型件从预成型站输送到注入站，而不会引入缺陷。此外，壳然后可以用于通过注入方法形成用于系统的基质材料到干燥的预成型件中。这一概念将允许去除粘合剂的使用，既允许提高最终部件质量又允许增加制造量。可以采用传统的大体积塑料成型工艺（例如，注射成型）来形成薄壳，并且因此这些薄壳应该能够快速地并且以较低的成本制造。这个概念的变化也可以探索，包括可重复使用的外壳，可以清洗和多次使用，或外壳设计，以提供特定的表面光洁度。博士项目进行的目的是调查这一概念的过程和可能的材料的可行性。目标包括（但不限于）：* 研究当前和潜在的未来制造工艺并确定一套指导方针 * 研究可用于形成壳体的合适材料 * 开发和验证材料选择 * 证明利用该壳体的加工概念的可行性 * 确定要使用的注入方法并努力优化这些方法 * 调查自动化该概念的方法因此，可以看出，正在对该概念进行调查，以发现该概念是否能够在大批量制造技术的性能中提供破坏性的阶跃变化。

During the manufacture of composite parts utilising direct impregnation/Liquid Composite Moulding techniques, the dry laminate is held to shape utilising tackifiers (or 'binders'). This allows the dry material to become what is termed a 'preform'. Preforming of the dry material serves two key purposes: firstly, it allows the preform to hold its shape before full impregnation has taken place. This helps to prevent generation of defects in the preform due to handling and transportation of the preform, alongside allowing a decrease in bulk factor and the possibility of damage to the tool. Secondly, preforming allows more efficient utilisation of equipment; the infusion equipment can be dedicated just to infusion/cure, as opposed to shaping as well. This is opposed to the manufacturing techniques utilised traditionally with prepreg materials, and is crucial to the upscaling of any manufacturing process towards a high-volume, automated assembly line type process.However, the use of binders to stabilise the preform also provides a number of problems. A key issue when utilising binder materials is the large time cost of 'activation' and cooling of the binder materials, contributing to over half of the time cost of a typical HP-RTM part. It follows therefore that the removal of this can vastly reduce takt time for these parts and allow significant increases in the volumes of parts it is possible to produce. Further, the use of binder materials has also been shown to reduce the permeability of the cloth, leading to lower impregnation, as well as lowering the quality of the final part by introducing material other than the fibre or matrix within the bulk structure. As such, it can be seen that removal of these stabilisers can lead to both drastic increases in production volume and an increase in the quality of the final part. A novel method of achieving this is the focus of the work set out here.In order to achieve binder removal, a new concept termed the "Clamshell Concept" has been envisioned. This concept aims to include no form of traditional binder whatsoever. Instead, a pre-made external shell structure shall be utilised to hold and clamp the preform into shape. This then will allow transportation of the preform from the preforming station to the infusion station without the introduction of defects. Further, the shell can then be utilised to form the matrix material for the system, through an infusion method into the dried preform. This concept will allow the removal of the use of binders, both allowing an increase in final part quality and manufacture volumes. Tradition high volume plastic forming processes can be employed (e.g. injection moulding) to form the thin shells, and as such these should be able to be manufactured rapidly and with less cost. Variations of this concept can also be explored, including reusable shells that can be washed out and utilised many times, or shells designed to give a specific surface finish.The PhD projection undertaken will aim to investigate the feasibility of both the process and possible materials for this concept. Objectives include (but are not limited to):* Research current and potential future manufacturing processes and determine a set of guidelines* Research suitable materials that can be used to form the shell* Develop and characterise the material choices* Demonstrate the feasibility of the processing concepts utilising this shell* Determine the infusion methods to be used and work towards optimising these* Investigate methods of automating this conceptAs such, it can be seen that investigation of this concept is taking place to discover if this concept is capable of providing a disruptive step change in the performance of high-volume manufacture techniques.