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

诸如压力容器、例如航空航天应用中的壳结构和管道系统的保压管状结构可以有利地由纤维增强聚合物复合材料生产。这些结构通常优于传统的金属部件，这是由于有利的特性，包括高比强度、材料各向异性和在恶劣环境中上级的抗降解性。现代制造设备，如自动缠绕机或编织机，允许自动化和高效地生产管状形状。因此，可以获得性能、安全性和经济性的改进。然而，尽管有这些优点，有限的理解的复杂和相互作用的损坏机制和随之而来的故障可预测性不足，阻碍了纤维复合材料在高压应用中的广泛使用。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。诸如聚合物基质的破裂的微损伤事件可能导致刚度和强度的损失，以及导致结构的流体渗透，从而导致泄漏和二次损伤事件。预计将把关于微观损害事件的信息，如类型、程度、顺序、相互作用和相互连接，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，必须进行多轴载荷条件下的高级力学测试。随后的实验数据是必不可少的，使和验证进一步的分析，使用建模技术的基础上材料强度，断裂力学和流体力学理论。

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.