Influences of environmental conditioning and damage on the dispersive propagation and damping behaviour of Lamb waves in fiber reinforced plastics

在最初资助阶段的前18个月内（在编写本后续提案时已完成），研究了环境和载荷条件（湿度吸收、温度变化、静态和动态载荷）及其组合对纤维增强塑料中的波传播的影响。此外，如果波导状态已知，则创建了预测传播特性变化的方法，并补偿这些变化，从而能够使用兰姆波进行结构健康监测（SHM）。拟议的第二供资阶段最初包括原提案中计划在第25至36个月期间进行的一揽子工作，并根据第一阶段的调查结果进行了调整。这主要包括实验工作包的结论及其评价。此外，第一阶段的研究结果将用于开发/扩展方法，如果传感器响应因与损伤形成无关的因素而发生变化，则可以评估结构的健康状况。根据这些方法和实验结果，将制定指导方针，其中包含在现实条件下SHM传感器网络的设计规则。此外，还建议第二资助阶段包含新的工作包，这些工作包处理传感器响应对显示制造相关散射的因素的高灵敏度，这些因素在第一阶段已确定。这些因素包括局部纤维体积含量的变化（例如，由于纺织品间隙），纤维取向和粘合剂层性能。由于预计这些因素的影响本身是第一阶段所研究的环境条件的函数，因此还建议研究与制造相关的特性散射和湿度吸收（作为随层压板厚度变化的缓慢变化的影响的示例）和温度（作为变化非常快的因素的示例）的综合影响。计划使用简单板和包含结构不连续面的板进行实验，其中局部变化，非损伤相关变化（特别是湿度吸收）对波和结构不连续（反射，模式转换等）之间相互作用的影响特别感兴趣。最后，将扩展处理传感器网络设计指南创建的工作包，以包括上述影响因素，即与制造相关的属性分散与结构不连续和非破坏性环境条件相结合。为了实现这一目标，建议使用基于fe的方法来预测传感器响应复杂性极高的区域，并开发/研究定位SHM系统任务的方法，即通过限制其任务或波覆盖的区域。

Within the first 18 months of the initial funding phase, which have been completed at the time of preparation of this follow-up proposal, the influence of environmental and loading conditions (humidity absorption, temperature changes, static and dynamic loading), and combinations thereof, on wave propagation in fiber reinforced plastics was investigated. Additionally, methods where created to both predict changes to the propagation characteristics if the waveguides state is known and to compensate for these changes to enable the use of Lamb waves for structural health monitoring (SHM).The proposed second funding phase initially contains the work packages which were planned for the time between month 25 and 36 in the original proposal, adapted to the findings of the first phase. Primarily, this includes the conclusion of the experimental work packages and their evaluation. Additionally, the findings of the first phase are to be used to develop/extent methods that allow the evaluation of the structures health if the sensor response changes due to factors unrelated to the formation of damage. From these methods and the experimental findings, guidelines are to be developed which contain rules for the design of sensor networks for SHM under realistic conditions.It is furthermore proposed that the second funding phase contains new work packages which deal with the high sensitivity of the sensor responses to factors that show manufacturing related scatter, which were identified in the first phase. These factors include variation of the local fiber volume content (e.g. due to textile gaps), the fiber orientation and the adhesive layers properties. As it is expected that the impact of these factors is itself a function of the environmental conditions investigated in the first phase, it is also proposed to investigate the combined influence of manufacturing-related property scatter and both humidity absorption (as an example for a slowly changing influence varying over the thickness of the laminate) and temperature (as an example for a factor that can change very fast). Experiments using both simple plates and plates containing structural discontinuities are planned, with the influence of locally varying, non-damage-related changes (esp. humidity absorption) on interactions between wave and structural discontinuity (reflection, mode conversion etc.) being of special interest.Finally, the work package dealing with the creation of guidelines for the design of sensor networks will be extended to include the aforementioned influencing factors, namely manufacturing-related property scatter in combination with structural discontinuities and non-damaging environmental conditions. To achieve this, it is proposed to use both FE-based approaches to predict areas where the sensor responses complexity would be critically high and to develop/investigate methods to localize the SHM systems task, i.e. by limiting its task or the area covered by the waves.