High bio-content fibre composites

纤维增强塑料复合材料（FRP）大量用于工程应用，例如车辆结构。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衍生的热固性环氧聚合物。尽管FRP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，但其环境影响仍有显着改善的空间。该项目旨在通过使用具有可再生资源的材料（即生物基环氧聚合物和再生纤维素纤维）生产更可持续的复合材料，并确定这些材料替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以及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。环氧聚合物是热固性的，因此是固有的脆性材料，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）来改善其断裂韧性。纤维素是一种有吸引力的生物基材料，因为它表现出良好的机械性能，并且它是一种廉价且丰富的材料。然而，当用环氧聚合物加工纤维素材料时出现一些问题。纤维素是亲水性的，被水吸引，并且容易吸收水分（在复合材料中是不期望的，因为它降低性能）;而环氧树脂基质是疏水性的。这种表面性质的差异导致界面强度差和空气空隙。此外，纤维素经历颗粒-颗粒相互作用，这可导致附聚和差的分散。空气空隙和团块在材料中充当应力集中器，降低其强度和韧性。因此，重要的是要了解如何最大限度地减少这些缺陷，并优化纤维素颗粒的分散。在使用低成本灌注方法制造复合材料的过程中，大颗粒团聚体不能穿过纤维堆，从而导致填料沿着长度和穿过复合材料厚度的不良分布。应用于纤维素纤维和颗粒的表面处理可以同时减少纤维素-纤维素相互作用并改善纤维素-环氧树脂相容性，从而改善分散性并减少吸水性。然而，这些处理对纤维素本身的性质也有负面影响。机械方法，如过滤和搅拌将被实施，以减少聚合物基体中的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提高纤维素颗粒分散体在本体环氧树脂中的质量和均匀性，并作为复合材料基体。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粘合力。将量化纤维素颗粒在整个散装环氧树脂样品和纤维复合板中的分散。将测量环氧纤维素复合材料的机械和断裂性能，并将其与微观结构的变化相关联，以确定最佳加工条件。所得到的纤维素颗粒增韧复合材料的性能和环境影响，与生物基环氧树脂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.