Abstract
Structural health monitoring (SHM) is a challenge for many industries. Over the last decade, novel strain monitoring methods using optical fibers have been implemented for SHM in aerospace, energy storage, marine, and civil engineering structures. However, the practical attachment of optical fibers (OFs) to the component is still problematic. While monitoring, the amount of substrate strain lost by the OF attachment is often unclear, and difficult to predict under long-term loads. This investigation clarifies how different attachment methods perform under time-dependent loading. Optical fibers are attached on metal, thermoset composite, and thermoplastic substrates for distributed strain sensing. Strains along distributed optical fiber sensors (DOFS) are measured by optical backscatter reflectometry (OBR) and compared to contact extensometer strains under tensile creep loading. The quality of the bondline and its influence on the strain transfer is analyzed. Residual strains and strain fluctuations along the sensor fiber are correlated to the fiber attachment method. Results show that a machine-controlled attachment process (such as in situ 3-D printing) holds great promise for the future as it achieves a highly uniform bondline and provides accurate strain measurements.
Highlights
Maintaining the integrity of structural components and infrastructures over years of service is a considerable challenge, and many structural health monitoring (SHM) systems have been developed for this purpose
Relative-t2 strains represent the time-dependent strain mental strain measurements from three types of substrate specimens are presented by different optical fibers (OFs) attachment methods, separately; and (ii) spatial and temporal strain curves are accompanied by a coarse analysis of presented data
Attachment length (OF L) is nominally the same as EXT L of the extensometer; some adhesives flowed during the curing process, leading to a longer actual OF L for these attachments
Summary
Maintaining the integrity of structural components and infrastructures over years of service is a considerable challenge, and many structural health monitoring (SHM) systems have been developed for this purpose. The integration of OF sensors inside the component, or attaching them on the component surface, is still a challenge for many practical applications [1]. Structural engineering applications (concrete, timber, and steel) tend to adhere the OF directly on the surface by a rigid glue [2], pre-embed the OF in a package filled with rigid glue or soft rubber [5,6,7], or attach specialized optical cables to the component [8]. Similar methods are adopted for polymers and polymer composites [9,10]
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