High bio-content fibre composites

纤维增强塑料复合材料（frp）在车辆结构等工程应用中有着广泛的应用。在大多数情况下，这些复合材料包括由油和玻璃或碳增强纤维制成的热固性环氧聚合物。虽然frp带来的重量减轻可以提供更可持续的选择，例如通过减少燃料消耗，但其对环境的影响仍有显著改善的空间。该项目旨在通过使用可再生材料，即生物基环氧聚合物和再生纤维素纤维，生产更具可持续性的复合材料，并确定这些材料取代玻璃纤维增强塑料复合材料的可行性。在工程应用中，良好的机械强度和刚度，伴随着高断裂韧性，对于提供具有长使用寿命的弹性材料至关重要。环氧树脂聚合物是热固性材料，因此本质上是脆性材料，但可以通过添加增韧填料（例如微纤维素或纳米纤维素颗粒）来提高其断裂韧性。纤维素具有良好的机械性能，是一种廉价而丰富的生物基材料。然而，当用环氧聚合物加工纤维素材料时，会出现一些问题。纤维素是亲水的，被水吸引，并且很容易吸收水分（复合材料中不希望的，因为它会降低性能）；而环氧基是疏水性的。这种表面性能的差异导致界面强度差和空气空洞。此外，纤维素经历粒子间的相互作用，这可能导致团聚和分散不良。空气空洞和团聚体在材料中起应力集中作用，降低了材料的强度和韧性。因此，了解如何将这些缺陷最小化并优化纤维素颗粒的分散是很重要的。在使用低成本灌注方法制造复合材料的过程中，大颗粒团块不能通过纤维堆，导致填料沿复合材料的长度和厚度分布不佳。对纤维素纤维和颗粒进行表面处理可以同时减少纤维素-纤维素的相互作用，改善纤维素-环氧树脂的相容性，从而改善分散性，减少吸水率。然而，这些处理也对纤维素本身的性质有负面影响。机械方法，如过滤和搅拌，将被用于减少聚合物基体中团聚体的大小和频率，以提高整体复合材料的性能。硅烷表面处理和颗粒分散方法将用于改善纤维素颗粒分散体在散装环氧树脂和复合基体中的质量和均匀性。表面处理也将用于改善环氧树脂和再生纤维素纤维之间的附着力。纤维素颗粒在散装环氧树脂样品和纤维复合板中的分散将被量化。将测量环氧-纤维素复合材料的力学和断裂性能，并将其与微观结构的变化联系起来，以确定最佳的加工条件。由此产生的纤维素颗粒增韧复合材料的性能和环境影响，与生物基环氧基基体和纤维素增强纤维，将与传统的玻璃纤维增强塑料复合材料进行比较。

Fibre reinforced plastic composites (FRPs) are heavily used in engineering applications such as vehicle structures. In most cases these composites comprise thermosetting epoxy polymers derived from oil and glass or carbon reinforcing fibres. Although the weight saving due to FRPs can offer a more sustainable option, e.g. by reducing fuel consumption, there is room for significant improvement in their environmental impact. This project aims to produce more sustainable composites by using materials with a renewable source, i.e. bio-based epoxy polymers and regenerated cellulose fibres, and to determine the feasibility for these to replace glass fibre reinforced plastic composites. In engineering applications, good mechanical strength and stiffness, accompanied by a high fracture toughness, are essential to provide a resilient material with a long service life. Epoxy polymers are thermosets so are inherently brittle materials, but it is possible to improve their fracture toughness by adding toughening fillers, e.g. microcellulose or nanocellulose particles. Cellulose is an attractive bio-based material as it exhibits good mechanical properties, and it is a cheap and abundant material. However, some issues arise when processing cellulosic materials with epoxy polymers. Cellulose is hydrophilic, attracted to water, and readily absorbs moisture (undesirable in composites as it degrades performance); whereas the epoxy matrix is hydrophobic. This difference in surface properties leads to poor interfacial strength and air voids. Also, cellulose experiences particle-particle interactions which can lead to agglomeration and poor dispersion. Air voids and agglomerates act as stress concentrators in the material, reducing its strength and toughness. Therefore, it is important to understand how these defects can be minimised and the dispersion of the cellulose particles can be optimized. During the manufacture of composites using low-cost infusion methods, large particle agglomerates cannot pass through the fibre stack, yielding a poor distribution of filler along the length and through the thickness of the composite. Surface treatments applied to cellulosic fibres and particles can simultaneously reduce the cellulose-cellulose interaction and improve cellulose-epoxy compatibility, hence improving dispersion and reducing water absorption. However, these treatments also have a negative effect on the properties of the cellulose itself. Mechanical methods, such as filtration and agitation will be implemented to reduce the size and frequency of agglomerates in the polymer matrix to improve the overall composite performance. Silane surface treatments and particle dispersion methods will be used to improve the quality and uniformity of cellulose particle dispersions in bulk epoxy and as a composite matrix. Surface treatments will also be applied to improve the adhesion between epoxy and regenerated cellulose fibres. The dispersion of cellulose particles throughout bulk epoxy samples and fibre composite panels will be quantified. The mechanical and fracture properties of the epoxy-cellulose composites will be measured and related to changes in microstructure to determine the optimum processing conditions. The properties and environmental impact of the resulting cellulose particle toughened composites, with a bio-based epoxy matrix and cellulose reinforcing fibres, will be compared to conventional glass fibre reinforced plastic composites.