Damage characterisation of fibre polymer composites for high-pressure retaining structures

保压管状结构，如压力容器、航空航天应用中的壳体结构和管道系统，可以由纤维增强聚合物复合材料制成。这些结构通常优于传统的金属部件，因为它们具有高比强度、材料各向异性和在恶劣环境下抗降解的优异性能。现代制造设备，如长丝缠绕机或编织机允许自动化和高效的管状生产。因此，在性能、安全性和经济性方面可以得到改进。然而，尽管纤维复合材料具有这些优势，但由于对其复杂和相互作用的损伤机制的了解有限，以及随之而来的失效可预测性不足，阻碍了纤维复合材料在高压应用中的广泛应用。这项研究工作的目的是提供一个更好的理解和预测所涉及的损害事件。聚合物基体的开裂等微损伤事件可能导致刚度和强度的损失，并导致流体渗透到结构中，从而导致泄漏和二次损伤事件。预计将微损伤事件的信息，如类型、程度、顺序、相互作用和相互联系，与宏观特征，即刚度、强度和渗透性的演变联系起来。为了研究损伤行为，必须进行多轴加载条件下的高级力学测试。随后的实验数据对于使用基于材料强度、断裂力学和流体力学理论的建模技术进行进一步分析和验证至关重要。

Pressure-retaining tubular structures such as pressure vessels, shell structures in e.g. aerospace applications, and pipe systems could be advantageously produced from fibre-reinforced polymer composites. These structures frequently outperform traditional metallic components, owing to favourable properties including high specific strength, material anisotropy and superior resistance against degradation in harsh environments. Modern fabrication equipment such as filament-winding or braiding machines allow for the automated and efficient production of tubular shapes. As a consequence, improvements in performance, safety and economy may be obtained. However, despite these advantages, a limited understanding of the complex and interacting damage mechanisms and ensuing inadequate failure predictability, have hampered the extensive usage of fibre composites in high-pressure applications. This research work aims at providing a better understanding and predictability of the involved damage events. Micro-damage events such as the cracking of the polymer matrix may cause a loss in stiffness and strength as well as lead to a fluid permeation of the structure causing leakage and secondary damage events. It is anticipated to relate information about micro-damage events, such as type, extent, sequence, interaction and interconnectivity, to macroscopic characteristics, i.e. the evolution of stiffness, strength and permeability properties. To investigate the damage behaviour, advanced mechanical testing under multiaxial loading conditions must be conducted. Ensuing experimental data are essential to enable and verify further analyses using modelling techniques based on strength-of-materials, fracture mechanics and fluid mechanics theories.