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

复合材料在交通运输行业中的结构应用越来越多，因为它们具有良好的机械性能(高刚度和高强度)，而且重量轻。它们可以节省燃料并提高性能。然而，复合材料构件在弯曲载荷作用下容易发生分层损伤。由于这个问题，局部受损的区域可能会危及整个结构，这会导致过早更换大型结构部件，由于浪费材料，会造成明显的经济和生态成本。因此，一个可行的选择是修复损坏的部件。粘接正成为最适合和最有吸引力的连接和修复复合材料部件的技术之一，它已被证明是非常有效的(粘接区域上的应力分布均匀，重量损失较小，抗疲劳和耐腐蚀性能较高)。然而，在完全实施之前，有必要充分了解其在疲劳下的行为，疲劳是运输行业中的一种主要载荷类型。在这些应用中，结构还经常处于恶劣的环境中，因此有必要评估湿热条件(湿度和温度)对其力学行为的影响。因此，重要的是开发考虑到环境和疲劳的综合影响的数值预测工具。然而，这样的数值工作相当稀少，而且大多数工具都是半经验的；这意味着它们需要广泛的实验测试来微调模型。目前的提议旨在开发一个包含骨折、疲劳和环境退化影响的渐进损伤模型。这样的模型将基于从适当的关系中得出的适当的“老化因子”，如Fickian扩散模型和实验的巴黎曲线。

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.