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(A and D) Ultrasonic C-scan images of specimens N80, P80, M80, and MP80. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
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Carbon fiber/epoxy composite specimens are manufactured using liquid resin infusion and incorporate a copper wire mesh on the outer layer for lightning strike protection. The specimens are then painted in order to be representative of an aircraft skin. The specimens are subjected to a scarf repair, which removes a portion of the wire mesh and of th...
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This paper presents the characterization of electro-magnetic (EM) performance of conductive composite laminate in consideration for aeronautic design. Novel nanocomposite resin was prepared by incorporating nanofillers into neat epoxy, resulting in remarkable improvement of its electrical conductivity. The planar structure of conductive composite l...
Citations
... The internal damage mechanisms resulting from resistive heating and impact due to lightning strike have been described in detail by several researchers [4][5][6][7]. Lightning protection solutions have been proposed and studied [7][8][9][10][11]. However, lightning strike continues to damage CFRP structures and cause outages to aircraft and wind turbine (WT) blades Thermography techniques are typically categorized as either active or passive, characterized by their operational principles and applications. ...
Carbon fibre reinforced polymers (CFRP) structures, e.g., wind turbine blades, are suspectable to direct lightning strikes due to their semiconductive nature and ability to conduct current. It is critical to identify and evaluate lightning damage as it can cause premature failure of the primary load carrying components. Direct strike lightning damage has been traditionally identified and assessed by ultrasonic (UT) inspection, which is time consuming, usually requires contact, and does not directly provide a measure of damage severity. An appealing alternative to UT is pulsed thermography (PT), which takes minutes to conduct rather than hours and does not require a couplant. The aim of this work is to explore the application of pulse thermography to identify and evaluate the damage state of CFRP panels damaged by simulated lightning strike. A new analysis technique is presented that provides a damage severity metric which allows damage to be categorized, separated, and quantified.
... Destructive and nondestructive evaluations are widely used to assess lightning damage in laminated composites [28][29][30][31][32][33][34][35][36]. For instance, Feraboli et al. [28] used pulse-echo ultrasonic inspection and optical microscopy to examine the lightning damage in 16-ply [45/0 2 / − 45/0 3 /90] s G30-500/7714A carbon-epoxy composites subjected to simulated lightning strikes with peak currents in the range of 10-50 kA. ...
Lightning damage to composite aircraft structures results from a concurrent and sequential interaction between arc discharge multi-physics and the anisotropic electrical and thermal composite properties. In this study, the impact of nominal 50 and 125 kA lightning strikes on damage formation in a carbon-epoxy Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) was investigated. A combination of visual inspection, ultrasonic phased array testing, destructive sectioning, and various microscopy techniques was employed to characterize the damage. Localized damage, including severe matrix decomposition, melting of polyester warp-knitting yarns, fiber splitting, and large-scale delamination, was confined to the immediate vicinity of the lightning attachment point and was accompanied by more diffuse surface damage (i.e., widespread small-scale split fiber tufts and surface primer scorching). The severity and extent of internal damage increased with higher lightning current intensities but were limited to the outermost nine-ply warp-knitted skin stack. Electrically non-conductive through-thickness Vectran™ stitches and polyester warp-knitting yarns had a profound effect in mitigating lightning damage formation. These results suggest that such through-thickness reinforcement can dramatically enhance the lightning damage resistance and tolerance of composite aircraft structures.
... Compared with metal materials, CFRPs contain random microcracks, and their conductivity is poor; thus, delamination damage occurs easily during lightning strikes. The occurrence of delamination damage in CFRPs is a major defect and failure mode under these conditions [1][2][3]. Millen and Murphy reported that changes in the inter-ply contact can affect damage area and depth predictions [4]. Therefore, the factors that influence lightning damage need to be determined [5,6]. ...
Internal delamination damage in carbon fibre reinforced polymer (CFRP) composites occurs easily after a fastener is installed. To determine the internal delamination damage in CFRPs with a fastener under lightning strike conditions, an experiment was conducted with different lightning channel gaps, fastener diameters, and fitting conditions. On the basis of the experimental findings and the results of a coupled thermal–electrical simulation model, a circuit model for CFRPs with a fastener was established to explore the current path, delamination properties and internal damage in CFRP specimens. The factors influencing the correlations between the generation and development of internal delamination damage under multiple conditions were proposed to clarify the lightning damage mechanism of the CFRP composites. The results indicated that internal delamination damage was mainly caused by resin pyrolysis and pyrolysis gas expansion; in addition, the thermal–electrical coupling effect of the contact interface had a significant impact on the internal delamination damage. For example, at approximately 50 kA, the damage area of the specimen with a 6 mm diameter fastener was 28.5% smaller than that of the specimen with a 4 mm diameter fastener. This work provides a basis for understanding the propagation of delamination in CFRP composites with a fastener and for reducing the delamination damage under lightning strike environment.
... At the same time, the survivability of polymer matrix composites subjected to harsh environmental conditions is still of concern. Lightning strikes [2] are high-risk and low-probability (e.g., one and a half strikes per year per airplane) events that present significant threats to polymer matrix composite structures. Carbon fiber-polymer matrix composites (CFRP) are particularly vulnerable to high-energy lightning strike events due to their relatively low electrical and thermal conductivities as well as limited service temperature and significant degradation in properties above the decomposition temperature. ...
... The last question is related to the relevance of simulated lightning strike tests to composite structures. A lightning strike causes local damage to various types of composite structures, such as protected CFRP composites with expanded copper mesh, unprotected CFRP composites, composites with and without paint layers [24,29,30,[68][69][70][71][72][73][74], composites with vertically interleaved fibers [74], composites containing electrically conductive nanofillers [75][76][77][78] and single-walled CNT tuball paper [79], composites with conductive coatings [80,81], metal-tufted composites [82], thermoset and thermoplastic composites [50,83], sandwiched composites [84], stitched composites [85], scarf-repaired composites [2], composites with mechanical fasteners [27], and adhesively bonded composite [86], as well as full-scale composite structures, such as wind turbine blades [18,[87][88][89]. Although existing simulated lightning strike experimental studies for CFRP composites primarily focused on unprotected and protected composites and composites with mechanical fasteners, the other composite structures are also of significant importance. ...
Lightning strike events pose significant challenges to the structural integrity and performance of composite materials, particularly in aerospace, wind turbine blade, and infrastructure applications. Through a meticulous examination of the state-of-the-art methodologies of laboratory testing and damage predictive modeling, this review elucidates the role of simulated lightning strike tests in providing inputs required for damage modeling and experimental data for model validations. In addition, this review provides a holistic understanding of what is there, what are current issues, and what is still missing in both lightning strike testing and modeling to enable a robust and high-fidelity predictive capability, and challenges and future recommendations are also presented. The insights gleaned from this review are poised to catalyze advancements in the safety, reliability, and durability of composite materials under lightning strike conditions, as well as to facilitate the development of innovative lightning damage mitigation strategies.
... In another experimental study, Martins et al. [57] obtained the value of the pressure loading of lightning for different lightning currents by using EMMA and SuperDICOM (SDICOM) lightning high current generators at four instants, t ¼ 6; 9, 14; and 26 μs: In this experimental study, the generators were permitted to transmit intense currents by a conduction electrical arc on a test sample connected to a rig made of aluminum plate. The magnitudes of the pressure loading models obtained in the experimental studies and the magnitudes of the IEPIM were evaluated for 100 kA lightning current in Table 7 and for 200 kA lightning current in Table 8, in terms of relative errors at the instants t ¼ 6; 9, 14; and 26 μs. ...
Lightning is one of the natural hazards that any aircraft may encounter while navigating. If adequate precautions are not taken against lightning, structural damage, operational disruptions, and loss of life and property can occur. Thus, studying the mechanism of damage caused by lightning strikes in an aircraft’s structural material is necessary to optimize the structure, minimize the damage, and reduce the cost caused by lightning. In the present article, the lightning-induced damage behavior of an aircraft structural material was investigated from an analytical perspective. For this purpose, two analytical-based models were developed: an improved electromagnetic pressure impact model (IEPIM) and the damage model in an aircraft wing. For the IEPIM, the findings of the article showed that the proposed pressure model is in good agreement with the experimental studies, borrowed from the open literature, for 100 and 200 kA lightning current. For the damage model, the findings of the article indicated that (i) even though lightning strikes to the regions with the same characteristics on an aircraft wing in terms of the lightning strike zone, the amount of deflection in the wing increases as the impact point approaches the wing tip and decreases as it approaches the wing root, (ii) without changing the lightning strike point ( x 0 ), when the damping coefficient ( ξ ) is increased in the range of 0 , 2 ξ , the amount of deflection decreases as the amount of damping coefficient increases, and (iii) when lightning with a current of 100 kA hits to the wing root of an aircraft, the pressure impact of the lightning causes more torsion deflection than bending deflection at the wing root; however, when it hits to the mid-wing or wing tip of an aircraft, the pressure impact of the lightning causes more bending deflection than torsion deflection at the mid-wing or wing tip.
... Several thousands of aircraft equipped with composite wings are currently flying with thousands of square meters of copper mesh embedded just beneath the surface of composites parts [28][29][30][31][32]. ...
In the context of carbon fibre reinforced polymer (CFRP) manufacturing process, conventional online cure monitoring techniques are usually based on expensive measurement systems using dedicated sensors. In this article, an innovative real-time cure monitoring method using electrical impedancemetry (EI) and the self-sensing material is introduced.
This paper is divided into five sections. The first section introduces the context of our study dealing with the monitoring of the cure of structural composites made of carbon fibres and thermoset matrix. The second section presents a brief state of the art and our previous published results on the subject. The third section deals with the materials used in this study, and the design and the production of an ad-hoc EI bench. The fourth section proposes the comparison between results obtained on CFRP and unreinforced matrix samples using conventional DSC and EI measurements. A conclusion and some prospectives close the paper.
A home-made, low-cost, multi-channel and multi-physics bench was developed for simultaneous testing of several samples, including CFRP laminates and unreinforced matrix. This approach not only makes it possible to monitor the degree of cure α (DOC) by the EI and the oven temperature, but also to detect potential cure cycle issues. The EI results are in good agreement with α obtained by rheometry and differential scanning calorimetry (DSC).
The proposed approach enables the identification of the most critical points of thermoset matrix composite polymerization: Liquefaction (PL), Gelation (PG), Vitrification (PV) and Finish of reaction (PF). Compared to the results of a preliminary study, a similar behaviour is obtained on different CFRPs (commercial references Hexcel composites T700/M21 and CTMI NC66/1808NA laminates) using two different benches. This clearly highlight the value and the quality of the proposed approach.
The experimental validation of our approach will contribute to the Structures Health Monitoring (SHM) of CFRP and the functionalization of carbon/epoxy composites. These results will be used in future works for refining electrical-mechanical modelling not only during curing but also during mechanical loading.
... Given the characteristics of DFMF, surface coating can improve the static electricity of the fiber surface and repair damaged fibers (Ji et al. 2021, Kawakami andFeraboli 2011). Introducing appropriate functional groups will also enhance the interaction with bitumen components (Levitt andPerutz 1988, Xing et al. 2022). ...
Since the outbreak of the COVID-19 pandemic, the discarded face masks have attracted widespread attention in society. In line with sustainable development, a physicochemical treatment method was used to recycle discarded face masks into styrene–butadiene–styrene (SBS) modified bitumen. Utilizing the highly adhesive polydopamine-polyethyleneimine (PDA-PEI) coating, it has improved the surface damage of the discarded face mask fibers (DFMF) caused by natural aging and mechanical fragmentation, simultaneously strengthening the connection between the fibers and bitumen. At 46 °C, the 2% embellish-face mask fiber (E-FMF)/SBS modified bitumen, compared to the 2%DFMF/SBS modified bitumen, exhibited improvements in complex modulus (G*), elastic modulus (G′), and loss modulus (G″) by 12.27%, 16.39%, and 13.35%, respectively. Furthermore, at 0.1 kPa and 3.2 kPa, the creep recovery rate (R) increased by 23.3% and 32%, and the average creep compliance (Jnr) decreased by 54.7% and 64%. It was demonstrated that DFMF adhered with the coating, were more effective in improving the mechanical properties, deformation resistance, and shear resistance of the bitumen. This approach enriches the application scenarios of discarded single-use face masks and supports environmental protection and road construction.
Graphical Abstract
... ECF protective layers offer a good protection against damage from direct lightning strike, but add a significant weight penalty to composite structures due to their manufacturing process [11]. In addition, repairs of the outer layer after lightning events are complicated due to the need to correctly re-establish the conductive network in the copper foil [12]. Thus, despite the very good protection they offer, there is a need to search for new protective coatings to overcome the downsides of ECF. ...
... In real aerospace structures, some sort of lightning strike protection system is integrated into the composite structure in order to avoid severe structural damage in the event of a lightning strike. Typically, this lightning strike protection consists of metallic meshes or foils (typically made from aluminum or copper) [17][18][19][20]. In order to account for this industrial practice, additional panels are produced featuring a layer of copper mesh The data typically reported for such experiments include in situ and ex situ data. ...
... In real aerospace structures, some sort of lightning strike protection system is integrated into the composite structure in order to avoid severe structural damage in the event of a lightning strike. Typically, this lightning strike protection consists of metallic meshes or foils (typically made from aluminum or copper) [17][18][19][20]. In order to account for this industrial practice, additional panels are produced featuring a layer of copper mesh protection. ...
In this manuscript, Current Component A lightning strike tests on three different types of carbon fiber reinforced composite panels are analyzed. The panels feature different levels of lightning strike protection: no protection, medium protection and heavy protection. In particular it was analyzed if there were any direct correlations between the peak electric current of the artificial lighting strike and the recorded velocities at the back surface of the composite panels. The existence of a master curve correlating the peak electric current, the mass of the composite panels and the measured back surface velocity was demonstrated. This finding implies that the back surface velocity correlates linearly to the inertia of the panel and the peak current of the lightning strike.
... One common issue in the application of carbon fibre reinforced polymers (CFRPs) is their inherently low electric conductivity, especially in their through-thickness direction [1,2,3], which poses challenges for protection against lightning strikes, electromagnetic interference, and high energy electromagnetic radiation [4,5,6] in aircraft, spacecraft, wind turbines, and all-electric vehicles [7,8,9,10]. For example, without adequate conductive protection, lightning strikes can result in severe structural damage and potentially catastrophic consequences [11,12,13,14]. To address this issue, copper or aluminium expanded foils are added on the external surface of composites [15,16] to conduct the lightning current and thus avoid potential damages to the aircraft. ...
