Modelling the effect of voids in Composite Components

减少航空航天和可再生能源部门对环境的影响的关键战略之一是用先进的纤维增强复合材料取代金属合金。这种材料不仅通过更轻的重量和改进的气动弹性行为提供直接的性能好处，而且还通过更高的耐用性(例如更好的耐腐蚀性和抗疲劳性)和更低的制造总体能源需求提供相当大的生命周期好处。然而，使用复合材料的缺点之一是它们对制造缺陷特别敏感，最常见的是由于最终固结过程中气体的捕获或沉淀而导致的气孔。为了达到可接受的生产成本或废品率，必须容忍一定程度的材料孔隙率，这通常是通过引入保守的设计允许量和安全系数来实现的，这些安全系数大多基于经验方法。保守的设计规则往往会首先否定采用复合材料的好处，这个问题可能会变得至关重要，因为传统的高压灭菌器制造被更节能的“非高压灭菌器”制造技术所取代。该项目将专注于开发新的多尺度分析方法来预测复合材料结构的制造宏观力学性能，同时考虑到详细的(中、微观)孔隙率特征，如局部孔洞含量(相对于零件几何形状)、局部孔洞大小和形貌的分布，以及空洞相对于中、微观材料结构的位置。该项目建立在该研究小组以前的工作基础上，这些工作包括孔隙度表征、过程建模以及复合材料中损伤和断裂的多尺度分析。将结合和进一步发展最先进的技术，包括(但不限于)：-复合材料的过程建模，以预测微观尺度(单独的纤维)、较低的中间尺度(单独的纱线或纤维束)、较高的中间尺度(单独的层或层)和宏观尺度(部件级)的成品材料结构；-高性能计算技术和软件，用于分析微观和中观尺度的损伤和断裂，能够分析数千种不同的材料和加载结构，考虑材料的可变性和其他不确定性，与统计推理方法相结合，可用于实验设计分析；-基于响应面方法和/或机器学习的多尺度建模策略，以适用于复合材料部件的详细设计和制造设计的宏观预测模型的形式实施上述学习/推断的材料行为。这种建模能力有可能取代目前在解决复合材料制造缺陷方面涉及的大部分经验主义，导致更快的设计周期、更少的物理测试、更准确的设计安全系数、更低的废品率，以及就其生命周期碳足迹而言更有效的复合材料结构。该项目主要属于EPSRC的研究领域“材料工程-复合材料”。这项工作是在布里斯托尔大学与BAE系统公司合作进行的，根据CER测试计划拨款(EPSRC编号18939/052018年-4088号)。

One of the key strategies in reducing the environmental impact of the aerospace and renewable energy sectors is to replace metal alloys with advanced fibre-reinforced composites. Such materials offer not only immediate performance benefits through lighter weight and improved aero-elastic behaviour, but also provide considerable life-cycle benefits through greater durability (e.g. better corrosion and fatigue resistance) and lower overall energy requirements for manufacture. One of the downsides of using composites, however, is their particular susceptibility to manufacturing defects, most commonly porosity caused by the entrapment or precipitation of gasses during final consolidation. In order to achieve acceptable production costs or scrap rates, some level of material porosity must be tolerated, which is often done by the introduction of conservative design allowables and safety factors mostly based on empirical methods. Conservative design rules tend to negate the benefits of adopting composite materials in the first place, a problem which may become critical as traditional autoclave manufacture is replaced by more energy-efficient 'out-of-autoclave' manufacturing techniques. This project will focus on the development of novel multi-scale analysis methods to predict the asmanufactured macro-scale mechanical performance of composite structures taking into account detailed (meso- and micro-scale) porosity characteristics such as local void content (relative to part geometry), local distributions of void sizes and morphologies, and the location of voids relative to the meso- and micro-scale material architecture. This project builds on previous work by this research group on porosity characterisation, process modelling, and multi-scale analyses of damage and fracture in composites. State-of-the-art techniques will be combined and further developed, including (but not limited to): - Process modelling of composites to predict the as-manufactured material architecture at the micro-scale (individual fibres), lower meso-scale (individual yarns or fibre bundles), upper mesoscale (individual layers or plies), and macro-scale (component-level); - High Performance Computing techniques and software for the analysis of damage and fracture at the micro- and meso-scales, enabling the analysis of thousands of different material and loading configurations, accounting for material variability and other uncertainties, which in combination with statistical inference methods can be used in design-of-experiment analyses; - Multi-scale modelling strategies based on response surface methods and/or machine learning, to implement the learned/inferred material behaviour above in the form of macro-scale predictive models suitable for the detailed design and design-for-manufacture of composite parts. Such a modelling capability has the potential to replace much of the empiricism currently involved in accounting for manufacturing defects in composites, leading to faster design cycles, fewer physical tests, more accurate design safety factors, lower scrap rates, and more efficient composite structures in terms of their life-cycle carbon footprints. This project falls mostly within the EPSRC research area 'Materials Engineering - Composites'. The work is conducted at the University of Bristol in collaboration with BAE Systems plc under the CerTest Programme Grant (EPSRC no. 18939/05 2018-4088).