Developing a multifunctional, wireless sensor system for monitoring the process parameters during the production of carbon-fiber reinforced composites

在以前的项目中，通过将改进的反应动力学模型的固化曲线与介电常数曲线相关联，证明了树脂体系的固化度与其在24 GHz的介电特性之间的直接关系。此外，开发了一种新型的无电池无线24 GHz传感器，用于在线记录纤维复合材料结构中固化过程中的介电常数和温度，并在实验中成功地进行了测试。鉴于该传感器仅适用于非导电纤维增强复合材料(FRC)，本项目将研究该传感器在多大程度上能够成功地适用于含有导电碳纤维(CFs)的FRC，因为碳纤维增强复合材料结构必须在结构部件中以最高标准运行。碳纤维增强聚合物(CFRPS)的问题是传感器和扫描仪之间的无线电信号被导电纤维高度衰减。衰减主要取决于电磁场的偏振和纤维的排列，为了分类不同纺织层、纤维体积比和偏振的影响，将通过准光传输系统来表征在不同温度下固化和不固化的环氧树脂。这将决定在没有额外措施的情况下不能对材料进行辐照的配置。应通过在天线上方引入介质通道来提高透过率。为此，需要一种概念来建造通道并在结构注入之前准确地插入它们，以便将对周围部件的结构承载能力的任何影响降至最低。传感器的工作频率也应该增加，以便最大限度地减小传感器和通道的尺寸，从而缓和结构影响。由于新增加的要求，只有以前项目中传感器的基本工作原理才能应用于新项目。传感器本身和介质通道必须完全重新设计，首先需要设计一个链接的仿真模型来计算嵌入的传感器和相关通道对复杂结构的机械冲击，并确定传感器几何形状和边界层粘结的影响。基于传感器组件和结构力学的测试结果，最终的无线传感器将在纤维复合材料固化过程中进行设计、组装和测试。最后，该传感器将在实际输液过程中进行测试，以验证其实际可用性。

In a previous projec, a direct relation between the degree of curing of resin systems and their dielectric characteristics at 24 GHz was proven by correlating the curing curves of an innovate reaction kinetics model with permittivity curves. In addition, a novel batteryless, wireless 24GHz sensor for recording in-situ the permittivity and temperature during curing within a fiber composite structure was developed and successfully tested experimentally.Given that this sensor is suitable only for use in non-conductive fiber-reinforced composites (FRCs), the present project will investigate the extent to which it can be successfully adapted for use in FRCs with conductive carbon fibers (CFs), as carbon fiber reinforced composite structures must operate to the highest standards in structural components.The problem with carbon fiber reinforced polymers (CFRPs) is that the radio signal between sensor and scanner is highly attenuated by the conductive fibers. The attenuation depends mainly on the polarization of the electromagnetic fields and the fiber arrangement.In order to classify the effects of different textile layers, fiber volume ratios and polarizations, they will be characterized with, and without curing epoxy resin at different temperatures by means of a quasi-optical transmission system. This will determine at which configurations the material cannot be irradiated without additional measures. The transmissivity should be improved by introducing dielectric channels above the antennas. To this end, a concept is required for constructing the channels and for precisely inserting them before the structure is infused, so as to minimize any effects on the structural load capacity of the surrounding component. The sensor operating frequency should be increased, as well, in order to minimize the dimensions of sensor and channels – thus moderating the structural impact. Due to the newly added requirements, only the basic principle of operation for the sensor from the previous project can be applied in the new project. The sensor itself and the dielectric channels must be completely redesigned.A linked simulation model needs to be designed to first compute the mechanical impact of the embedded sensor and the associated channel on complex structures, and to determine the effects of sensor geometry and boundary-layer adhesion. The simulation thus supports the empirical optimization of sensor loading with respect to geometry and boundary layer.Based on the test results for the sensor components and structural mechanics, the final wireless sensor will be designed, assembled and tested in a fiber-composite curing process. Finally, the novel sensor will be tested in a real infusion process to verify its practical usability.