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Protection of Carbon Fiber Reinforced Polymer Matrix (CFRP) Composite Laminate Against Lightning Strike Using Nano-Fillers
... Carbon nanotubes (CNTs), due to their exceptional mechanical, electrical, and thermal properties, are attracting growing attention in the research community [1][2][3][4]. The mechanical properties associated with the CNT composites are influenced by the type and amount of CNT utilized in the composite. ...
Carbon nanotubes (CNTs), as they possess outstanding mechanical properties and low density, are considered as one of the most promising reinforcements in composite structures. Due to their capability of transferring loads, CNTs in long continuous forms such as yarns and tapes can withstand 20 times as much load as steel can do at the same weight. In this research, carbon nanotube yarns were wound onto an aluminum plate using a custom-built fixture to fabricate a unidirectional strip. Then, by brushing epoxy resin on the strip and laminating four layers, the unidirectional CNT reinforced epoxy resin composite beam specimens were produced. The mechanical properties of the unidirectional CNT-reinforced composite (CNTRC) were determined using standard tensile tests. This study presents a method for manufacturing CNTRC out of CNT yarns, determining the CNTRC's Young's modulus as well as the tensile strength, and obtaining its strain field via digital image correlation (DIC) method. It is observed that the pressure due to sandwiching of the aluminum plates during the manufacturing process leads to nonuniformity of the specimen in the width along midspan of the longitudinal direction which results in the specimen's not being perfectly unidirectional. This phenomenon can cause the matrix cracking in tensile test and reduce the ultimate tensile strength up to 78% in comparison with perfectly unidirectional specimens. However, the Young's modulus of such composites is comparable with those obtained from previously existing research. Also, Results from DIC showed the possible failure prone areas in the specimens, as it presents a up to 64% difference between the highest and lowest strain in the tensile loading direction through the specimens. This study will serve as a foundation for future research involving CNT composites, particularly the use of their high anisotropy to produce auxetic composites with large negative Poisson's ratios.
... This ensures that components are over-engineered for some of the most extreme lightning currents they may experience [10]. Experimentally, authors have studied the influence of novel Lightning Protection Systems (LSPs) [12][13][14][15][16][17], sequential strikes using multiple waveforms [18] or single strike tests [19]. Research on simulating the direct effects of lightning (physical damage) have predominantly focused on the thermal-electric effect in the specimen due to resistive or Joule heating [18,20,21]. ...
Research into residual strength after lightning strike is increasing within the literature. However, standard test methods for measuring residual compressive strength after lightning strikes do not exist. For the first time, a systematic experimental study is undertaken to evaluate modifications necessary to standard Compression After Impact (CAI) specimen geometry and test jig design to induce specimen failure at the lightning damage region. Four laboratory generated lightning strike currents with peak amplitudes ranging from 25 to 100 kA have been studied. Test set-up modifications were made considering the scale of the lightning damage and its potential proximity to specimen edges. Specimen geometry and anti-buckling guides were adjusted for each peak current to induce specimen failure at the lightning damage. The Compression After Lightning (CAL) strength was 28% lower than the pristine CAI strength even at a relatively low peak current of 25 kA. This study shows that the standard CAI test setup has the potential for CAL application, however, careful modifications are required depending on the peak amplitude of the applied lightning current waveform.
... This ensures that components are over-engineered for some of the most extreme lightning currents they may experience [10]. Experimentally, authors have studied the influence of novel Lightning Protection Systems (LSPs) [12][13][14][15][16][17], sequential strikes using multiple waveforms [18] or single strike tests [19]. Research on simulating the direct effects of lightning (physical damage) have predominantly focused on the thermal-electric effect in the specimen due to resistive or Joule heating [18,20,21]. ...
Trans-laminar fracture toughness is an important property of laminated composites and examining the fracture process zone at the tip of a crack is key to understanding it. To date, little research has been done on in-depth examination of the early fracture process zone development in quasi-isotropic laminates. In this work, detailed in situ X-ray Computed Tomography (CT) analyses enabled continuous examination under loading and better understanding of the entire fracture process zone development. Ex situ CT scanning of an additional hot temperature wet conditioned specimen with dye penetrant was also employed as a comparison to explain the significance of 0° splitting to trans-laminar fracture.
Carbon fiber composites are paving the way for light weight, high strength structures in the aerospace industry. While the benefits of carbon fiber composites are undeniable, they also have their drawbacks. Crippling damage due to lightning strikes is one of them. The current solutions to reducing the damage due to lightning includes adding expensive and heavy copper mesh into the laminate. A potential solution to this problem would be to add a lightweight conductive additive to the epoxy resin instead of a copper mesh. Carbon nanotubes are chosen as the additive to create an electrically conductive resin matrix and hence increase the overall electrical conductivity of the composite. Increasing the conductivity will decrease the damage owing to a faster dissipation of lightning-strike-induced Joule heating, and more importantly increase the residual strength. In this work, we quantified the increase in conductivity through measuring the electrical resistance using the four-probe method. Results showed that the electrical resistance of the sample with carbon nanotube additives is 31% lower than the one with no additives when the same resin system is used. In addition, lightning strike tests have also been carried out with both samples using an artificially generated waveform A impulse current with a peak of 100 kA. The current results showed no visible damage to both the samples with and without CNT additives in the epoxy. Time-resolved camera images taken for the lightning strike tests showed that the lightning current may have conducted through the metallic grounding device owing to the small planar sample size (i.e., 6 by 6 inches), which resulted in unsatisfactory test results.
Lightning strike damage tolerance of carbon fiber reinforced polymer (CFRP) composites is prone to misinterpretation. This study demonstrates that the design of lightning strike testbeds can be a major cause of the misinterpretation. The risk of misinterpretation originates from the lack of standards clearly defining testbed design requirements including electrode size and ground electrode edge configuration. Here we report the impact of electrode size and ground electrode edge configuration on the damage characteristics of CFRP matrix composite laminates caused by simulated lightning strikes. The results suggest that the level of damage is influenced by discharge current amplitude, discharge diameter, and the existence of electrical insulation covering ground electrode edges. Specifically, the damage increases with increasing discharge current amplitude and decreasing discharge diameter. Most importantly, we report that electrically insulating the edges of ground electrode prevents lightning discharge current from bypassing CFRP matrix composite laminate samples and directly striking the ground electrode. Experiments conducted without electrically insulating the edges resulted in considerably lower sample damages than those resulted from experiments conducted with the electrically insulated ground electrode edges. Our findings suggest that electrode size and ground electrode edge configuration have significant influence on the results of lightning strike experiments.
In recent years, Carbon Fiber Reinforced Plastics (CFRP) or Glass Fiber Reinforced Plastics (GFRPs) have become a very common material for aircraft and wind turbine structures. These structures are often protected from lightning strikes using conventional metal-based protective films/foils. Non-conventional, non-metallic lightning strike protection (LSP) technologies have not yet been fully realized, but research on non-conventional LSP systems for CFRPs has gained momentum in the last few years. The discovery of new structural conductive materials and improvements in the processing of carbon nano-filler based composites have challenged the conventional metal-based LSP systems by providing the potential for lightweight, non-metallic alternatives. However, a major challenge in using non-conventional LSP is the complex nature of a lightning strike event and its complicated thermal and mechanical impact on CFRP structures. Understanding the direct effect of a lightning strike on a CFRP structure requires understanding multiple transient loads, such as electrical, thermal, magnetic, acoustics, shock, and inertia. This review article focuses on new findings and discusses the complex direct effects of lightning on CFRPs. The focus is to find the important factors that regulate and control the damage to FRPs are classified and discussed with the help of available literature based on experimental results. Possibilities and limitations to these new findings are also discussed.
Laminated carbon/glass fiber reinforced polymer matrix composite structures experience rapid temperature rise, resin decomposition, delamination, thermal ablation, and possible dielectric breakdown subjected to lightning strikes. The predictive analysis of these damage is challenging due to the complicated electric-thermal-mechanical-chemical coupling effects. In this paper, the basic physics, problem formulations, and numerical approaches for such multiphysics analysis are thoroughly reviewed. Limitations of the existing problem formulations and numerical approaches are extensively discussed. Possible solutions to overcome those limitations and future directions on improving the fidelity and accuracy of such predictive analysis are also provided. In addition, part of the material properties that are required for these analyses, such as the temperature-dependent thermal, electrical, and mechanical properties of the composite lamina, the fracture properties of the interface resin, and the dielectric breakdown strength of the composite laminate are collected from various sources and are provided in this paper.
Composite Structures - The First 100 Years
- B Roeseler
- B Sarh
- M Kismarton
Gharghabi, Pedram. Experimental and Numerical Studies of Lightning Strike Induced Damage to Carbon Fiber Epoxy Composites. Mississippi State University, 2018
- Gharghabi Pedram