Browsing by Author "Ghadarah, Noor Salam"

Now showing 1 - 4 of 4
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    A comparative analysis of acoustic emission sensor embedding in glass fibre composite
    (Elsevier, 2023-12-21) Ghadarah, Noor Salam; Ayre, David
    The manufacturing process of composite structures permits fully embedding acoustic emission (AE) sensors. While the embedding process may pose challenges, its advantages, if proven, can outweigh the challenges. The increased sensitivity resulting from embedding acoustic emission sensors in composites is still not definitively established. A test was set up with pre-determined AE initiation locations (surface and sub-surface) and pre-determined receiving sensor's location (surface and sub-surface) to ensure any sensitivity increase was evident. The receiving sensor's attenuation along (at 90°) and across the fibres (at 45°) was assessed using two test methods: pencil lead breaking (PLB) and actuator methods. The actuator method involved using two pulse generators, the TGP110 pulse generator and the Mistras FieldCal. A range of specific frequencies were utilised, 30, 60, 150 and 300 kHz, using the FieldCal. The results obtained from the test methods were not in agreement with each other. For example, comparing the sensitivity using surface cracks, the PLB method showed decreased sensitivity when embedding the receiving sensor compared to the actuator method, which demonstrated minimal changes in sensitivity. The research aims to clarify the sensitivity increase obtained when embedding an AE sensor while taking into account the crack's position and frequency.
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    ItemOpen Access
    Performance evaluation of embedded acoustic emission sensors in a glass fibre composite under mechanical loading
    (Elsevier, 2024-01-18) Ghadarah, Noor Salam; Ayre, David
    Fully embedding acoustic emission (AE) sensors in a composite is postulated to increase the sensor’s sensitivity. The increased sensitivity will enable the sensor to detect subtle structural changes and lower the number of sensors required for monitoring. However, researchers have differed on whether the sensitivity increases or not. To robustly investigate the fully embedded AE sensor’s sensitivity, the surface and fully embedded AE sensors are placed on the same specimen, away from the high-stress region and compared based on the same hit. Two mechanical testing methods are used: three-point bend and double cantilever beam (DCB) mode I. Three sensors are embedded: lead zirconate titanate (PZT), gold-plated polyvinylidene difluoride (PVDF), silver-ink PVDF. The DCB mode I method showed that the sensitivity of the surface embedded sensor was generally better or equal to the fully embedded sensor. However, the three-point bend method showed similar sensitivity with both surface and fully embedded sensors. The results indicate that the fully embedded sensor’s sensitivity is based on the frequency of the AE event and, therefore, the failure type. The aim of the study is to analyse the sensitivity of the surface-embedded and fully embedded sensors concerning surface-originating and subsurface-originating cracks.
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    Performance evaluation of thin acoustic emission sensors in a laminated composite for structural health monitoring
    (Cranfield University, 2023-10) Ghadarah, Noor Salam; Ayre, David; Skordos, Alexandros A.
    Acoustic emission (AE) is a viable technique for structural health monitoring. Structures can be monitored by placing the AE sensors on the surface. However, with polymer-reinforced composites, it is possible to embed the acoustic emission sensor within the structure. The embedding process is postulated to increase the sensor’s sensitivity and thus detect subtle structural changes. However, researchers have differed on whether the sensitivity increases or not. To investigate the sensitivity of the sensors, the acoustic emission source used can be either artificial or natural. Artificial acoustic emission sources such as the pencil lead breaking and transducer methods were investigated for their precision and accuracy. To increase the versatility of the transducer method, repositionable double-sided and thin double-sided tapes were assessed as removable and repositionable couplants. The PLB and transducer methods were found to have different frequency responses on both the metal and the composite. The results also indicate that the transducer must be coupled permanently or at least not repositioned for best performance. The artificial acoustic emission sources, PLB and transducer methods were used to investigate the sensitivity of the fully embedded AE sensor. A test was set up with pre-determined AE initiation locations (surface and sub-surface) and pre- determined receiving sensor’s location (surface and sub-surface) to ensure any sensitivity increase was evident. The results indicated that the sensitivity of the sensors was influenced by the frequency of the artificial acoustic emission source. The sensitivity was then analysed using natural acoustic emission sources by inducing failure using mechanical loading. Two mechanical testing methods are used: three-point bend and double cantilever beam (DCB) mode I. Three AE sensors were tested. The results suggested that the sensitivity is more related to the crack’s frequency than the crack initiation point.
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    ItemOpen Access
    A review on acoustic emission testing for structural health monitoring of polymer-based composites
    (MDPI, 2023-08-04) Ghadarah, Noor Salam; Ayre, David
    Acoustic emission (AE) has received increased interest as a structural health monitoring (SHM) technique for various materials, including laminated polymer composites. Piezoelectric sensors, including PZT (piezoelectric ceramic) and PVDF (piezoelectric polymer), can monitor AE in materials. The thickness of the piezoelectric sensors (as low as 28 µm—PVDF) allows embedding the sensors within the laminated composite, creating a smart material. Incorporating piezoelectric sensors within composites has several benefits but presents numerous difficulties and challenges. This paper provides an overview of acoustic emission testing, concluding with a discussion on embedding piezoelectric AE sensors within fibre-polymer composites. Various aspects are covered, including the underlying AE principles in fibre-based composites, factors that influence the reliability and accuracy of AE measurements, methods to artificially induce acoustic emission, and the correlation between AE events and damage in polymer composites.