Light emitting composite beams during matrix cracking

Abstract

Defects in fiber-reinforced composite structures tend to initiate unpredictably and unalarmed due to local stress concentrations within a composite structure; this has given rise to active monitoring techniques that can quantify the mechanical stress within composites in order to evaluate the structural health. In this paper, triboluminescent mechanisms are used for damage monitoring of composite matrix under flexural loading. Vinyl ester resin is doped with ZnS:Mn phosphors and reinforced with glass fiber whiskers, were subjected to flexural loading while observing both the triboluminescent and acoustic response using a photo multiplier tube (PMT) and micro-mic respectively. Validity of triboluminescent emissions for determining structural integrity of glass fiber / vinyl ester resin composites through individual waveform analysis was examined. Understanding the failure modes through the captured waveform and observed triboluminescent emissions shows that the matrix cracking failure mode tends to lie in the natural frequency range of 2691–2813 Hz. High correlation between the triboluminescent and acoustic signals at matrix cracking at a frequency of 2800 Hz were found. Future research will discuss the triboluminescent and acoustic emissions behavior for delamination and fiber breakage failure modes.

Concrete–fiber-reinforced polymer interfacial bond monitoring with self-triggering sensors

“…Figure 18 shows a combination of the load curve, the audio signal, and the TL signal. The TL signals show similar correlation to the audio signal as observed in our previous work (Joshi et al, 2017). The work was conducted on ubiquitously distributed ZnS:Mn in a vinyl ester resin but nonetheless the emission mechanism show consistency whether ubiquitous or coated on an optical fiber as is in this work.…”

“…Thus, the sensor is able to differentiate between microcracks and major cracks just like an acoustic sensor. The critical advantage (Joshi et al, 2017) that the TL sensor has over the acoustic sensor is its ability to be embedded, thus providing information at the microlevel as compared to a surfacial level information which can be misleading.…”

Additive manufacturing of functional polymer-based composite with enhanced mechanoluminescence (ZnS:Mn) performance

“…By controlling the properties of the polymer matrix and the TL crystals, we can tune the sensitivity and working range of 3D printed parts. The results suggest that TL emission may reveal path crack propagation 39 since the emission is bound to occur upon the failure of ZnS crystals in the matrix. This research would provide a novel approach for the fabrication of embedded sensors for structural health monitoring of parts produced by additive manufacturing.…”