Multilayered Glass Filament Yarn Surfaces as Sensor Yarn for In-situ Monitoring of Textile-reinforced Thermoplastic Composites

High-performance textile filament yarns, more precisely glass filament (GF) yarn, were used as base material for the development of sensor yarns (SY) because GFs offer high tensile strengths and moduli of elasticity in addition to beneficial decomposition temperatures and elongation. The aim of this work was the creation of a multifunctional sensor yarn (MFSY) based of GF. To achieve this aim, a homogeneous, completely coated first (1st) and second (2nd) silver (Ag) layer was built on the GF yarn surface by developing new technologies. The 1st Ag layer monitors damage within the thermoplastic composite globally, whereas the 2nd Ag layer monitors it locally and defects interface damage. Also, there was an insulation layer between two Ag layers, leading to a total of three layers built on the GF surface. Its surface morphology was determined by light and scanning electron microscopy (SEM) to assess Ag layer properties, such as structure, homogeneity, and cracking. For structural analysis, GFs were investigated using a Fourier transform infrared spectrometer (FTIR). The Ag layer thickness was determined after coating and metallization. Textile-physical tests of the GF in terms of tensile strength, elasticity modulus, elongation at break, yarn fineness and electric conductivity, were carried out before and after silvering.