Damage Mechanisms in Loaded Aramid Composites by Means of Embedded PVDF Acoustic Emission Sensors

Abstract

Cost-effective and reliable damage detection is critical for the utilization of composite materials due to the relatively localised nature of damage formation and the resultant reduction in structural integrity. Of the methods available, Acoustic Emission (AE) is considered as one potential technology for on-line and in situ monitoring of structural degradation of composite materials. Purpose of this work was to study the interaction between embedded PVDF (polyvinylidene fluoride) transducers and composite samples as well as detect and characterize the failure mechanisms in aramid/epoxy flexural test specimens using acoustic emission data obtained by embedded PVDF film sensors. Furthermore, it has been realized a comparison with surface mounted PVDF data. Results of our previous works (Caneva et al., 2005) dealing with monitoring tensile and flexural behaviour of glass/epoxy composites enabled to extend this methodology to aramid/epoxy composites. The use of Acoustic Emission and Scanning Electron Microscopy (SEM) observations enabled to identify and understand the failure mechanisms of the composites tested. Furthermore, satisfactory results of this work highlighted that the application of PVDF shows promise as a suitable acoustic emission transducer for fibrous composite materials.

In Situ Damage Detection for Fiber‐Reinforced Composites Using Integrated Zinc Oxide Nanowires

“…Two common methods for in situ damage detection for fiber‐reinforced composites are acoustic emission testing (AET) and electrical resistance measurements. These methods are superior over alternative NDE methods in that they not only detect damage in situ, but recent developments have also demonstrated they can use embedded sensors thus eliminating the need for externally attached sensors and transducers …”

“…These alternative sensors were shown to be capable of detecting the same damage as commercially available piezoelectric sensors without the rigidity and brittleness of traditional lead zirconate titanate wafers; however, the sensors still required external bonding to the structure under inspection. To more fully overcome limitations placed by external bonding, optical fibers as well as PVDF film sensors have been researched as fully embedded sensors in fiber‐reinforced composites for AET . In both cases, the fully embedded AET sensor was able to detect damage; however, the nature of the sensors used required predetermined positioning and discrete placement in the structure during the manufacturing process.…”