Hygrothermal effect on the fracture/fatigue behaviour of adhesively bonded repairs

湿热效应对粘合修复的断裂/疲劳行为

• 批准号: 529660074
• 负责人: Professor Dr.-Ing. Joachim Hausmann
• 金额: --
• 依托单位: Leibniz-Institut für Verbundwerkstoffe (IVW)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/529660074?language=en
• 关键词: Hygrothermal; effect; fracture; fatigue; behaviour

Structural applications of composite materials have been increasing in the transportation industry because they present good mechanical properties (high stiffness and strength) associated with low weight. They enable fuel saving and performance improvement. However, composite components are prone to delamination damage, mainly under bending loads. Because of this issue, locally damaged regions can compromise the complete structure, which leads to premature replacement of large structural components with obvious economic and ecological costs due to waste of material. Therefore, a viable alternative is to repair damaged components. Adhesive bonding is becoming one of the most suitable and attractive techniques for joining and repairing composite parts and it has proven to be very effective (uniform stress distribution over the bonded area, less weight penalty and higher fatigue and corrosion resistance). Nevertheless, before its complete implementation, it is necessary to fully understand its behavior under fatigue, which is a predominant type of loading in the transportation industry. In these applications, structures are also frequently under severe environments, making it essential to evaluate the influence of hygrothermal conditions (moisture and temperature) on their mechanical behavior. Thus, it is important to develop numerical predictive tools that take into account the combined effect of the environment and fatigue. However, such numerical works are rather scarce and the majority of tools are semi-empirical; which means that they require extensive experimental testing to fine-tune the models. The current proposal aims to develop a progressive damage model incorporating the effects of fracture, fatigue and environmental degradation. Such model will be based on suitable “ageing factors” derived from appropriate relations as Fickian diffusion models and the experimental Paris curves.

复合材料的结构应用在运输行业中一直在增加，因为它们具有与低重量相关的良好机械性能（高刚度和强度）。它们可以节省燃料和提高性能。然而，复合材料构件容易发生分层损伤，主要是在弯曲载荷下。由于这个问题，局部损坏的区域可能会损害整个结构，这导致过早更换大型结构部件，由于材料浪费而造成明显的经济和生态成本。因此，一个可行的替代方案是修复损坏的组件。粘合剂连接正成为连接和修复复合材料部件的最合适和最有吸引力的技术之一，并且已被证明是非常有效的（在连接区域上均匀的应力分布，更少的重量损失以及更高的抗疲劳性和耐腐蚀性）。然而，在其完全实施之前，有必要充分了解其在疲劳下的行为，疲劳是运输行业中的主要载荷类型。在这些应用中，结构也经常处于恶劣的环境中，因此必须评估湿热条件（湿度和温度）对其机械性能的影响。因此，重要的是开发数值预测工具，考虑到环境和疲劳的综合影响。然而，这样的数值工作是相当稀缺的，大多数工具是半经验的，这意味着他们需要广泛的实验测试，微调模型。目前的建议旨在开发一个渐进损伤模型，包括断裂，疲劳和环境退化的影响。这种模型将基于从适当的关系导出的适当的“老化因子”，如Fickian扩散模型和实验巴黎曲线。