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

在之前的一个项目中，通过将创新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程度与其介电特性在24 GHz下的直接关系。此外，开发了一种新型无电池、无线24GHz传感器，用于记录纤维复合材料结构固化过程中的介电常数和温度，并成功进行了实验测试。鉴于该传感器仅适用于非导电纤维增强复合材料（FRCs），本项目将研究它在多大程度上可以成功地适用于导电碳纤维（CFs）的FRCs，因为碳纤维增强复合材料结构必须在结构部件中达到最高标准。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极化和光纤的排列方式。为了对不同纺织层、纤维体积比和极化的效果进行分类，我们将通过准光学传输系统对不同温度下环氧树脂固化和不固化的效果进行表征。这将决定在没有额外措施的情况下，材料在哪些构型下不能辐照。通过在天线上方引入介电通道，可以提高天线的透过率。为此，需要一个概念来构建通道，并在结构注入之前精确插入通道，以尽量减少对周围构件结构承载能力的影响。传感器的工作频率也应该增加，以尽量减少传感器和通道的尺寸，从而缓和结构的影响。由于新增加的要求，在新项目中只能采用上一个项目中传感器的基本工作原理。传感器本身和介质通道必须完全重新设计。需要设计一个相关的仿真模型，首先计算嵌入式传感器和相关通道对复杂结构的机械影响，并确定传感器几何形状和边界层粘附的影响。因此，模拟支持了传感器加载在几何和边界层方面的经验优化。根据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.