Techniques that monitor the change in the electrical properties of materials are promising for both non-destructive testing and structural health monitoring of carbon-fiberreinforced polymers (CFRPs). However, achieving reliable monitoring using these techniques requires an in-depth understanding of the impedance response of these materials when subjected to an alternating electrical excitation, information that is only partially available in the literature. In this work, we investigate the electrical impedance spectroscopy response at various frequencies of laminates chosen to be representative of classical layups employed in composite structures. We clarify the relationship between the frequency of the electrical current, the conductivity of the surface ply and the probing depth for different CFRP configurations for more efficient electrical signal-based inspections. We also investigate the effect of the amplitude of the input signal.
Laserbased surface preparation of composite laminates leads to improved electrodes for electrical measurements, Applied Surface Science (2015), http://dx.doi.org/10.1016/j.apsusc. 2015.10.086 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Page 1 of 32 A c c e p t e d M a n u s c r i p t
AbstractElectrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified.A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.
CitationAlmuhammadi K, Yudhanto A, Lubineau G (2018) Real-time electrical impedance monitoring of carbon fiber-reinforced polymer laminates undergoing quasi-static indentation. Composite Structures. Available: http://dx.
AbstractLaminated composites are vulnerable to damage from out-of-plane loading, particularly impact loading, and the incurred damage is often only detected by evaluating the postimpact condition of the composites. Real-time monitoring techniques are desirable for early detection of damage. Utilizing changes in the electrical properties of composites to track incurred damage is promising, but the interpretation of such measurements is still challenging. Here, an electro-mechanical system is introduced to understand how well we could detect mechanical degradation in carbon-fiber-reinforced polymer (CFRP) plates undergoing a quasi-static indentation (QSI) test, which is representative of an impact load.The system measures the in-situ, real-time changes in impedance and phase angle along the specified conductivity paths. Two different electrode configurations are proposed and tested. In all studied cases, the system effectively detected severe damage, characterized by an immediate reduction in strength, in CFRP. Using our proposed electrode configurations, we discovered that the early detection of barely visible damage strongly depends on two factors: (i) the location of the injection-measurement points with respect to the damage, *
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