No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Smart Protection of Carbon-Reinforced Composite Materials and CFRP-Metal Joints
Abstract
Smart protection of metallic materials is currently a hot topic in mitigation of corrosion of metallic structures, and promises reduction in both economic and environmental costs. Degradation of carbon-reinforced composite materials and CFRP-Metal joints is a serious issue in high-performance weight-optimized structures employed in the aeronautical and automobile industries. Since both carbon-reinforced composite materials and CFRP-Metal joints are ubiquitous in these critical industries, there is a need to develop strategies for smart protection of such complex multi-material systems. In this article, the current state of art/practice in protection of carbon-reinforced composite materials and CFRP-Metal joints is reviewed, the theoretical basis, intricacies and limitation of current practice (in protection of carbon-reinforced composite materials and CFRP-Metal joints) highlighted, distinction made between protection of materials and smart protection of materials, and the need for smart protection of carbon-reinforced composite materials and CFRP-Metal joints are emphasized. In addition, the background for smart protection of carbon-reinforced composite materials and CFRP-Metal joints is laid, and drawing from literature and results from our own research efforts perspectives on critical factors to be considered, and plausible strategies for smart protection of carbon-reinforced composite materials and CFRP-Metal joints is provided.
... Various techniques and metrics utilizing electro-mechanical impedance spectroscopy are presented to assess and characterize damage severity [43,45]. The conjunction of EMIS and Lamb wave was utilized to identify and locate damage produced by cyclic loadings in composite plates [46]. The EMI measurements were taken on a variety of samples, each reflecting a different amount of wear and wear position in the mechanical systems [47]. ...
The Fatigue crack represents one of the most likely reasons for metal structural failures. It is crucial to detect it effectively to avoid a disastrous tragedy. This paper presented a developed procedure to assess the structural integrity and identify the fatigue crack using local vibration techniques. The process includes building computational modeling and conducting experimental investigations to detect and visualize the interesting fatigue crack. The finite-element modal analysis was performed to predict the resonance frequencies which cause high local vibration over the damage domain and extract corresponding mode shapes. These numerical results were validated by conducting electromechanical impedance spectroscopy (EMIS) and the scanning laser Doppler vibrometer (SLDV) experiments based on a developed method. The electromechanical impedance spectroscopy experiment was implemented to predict the crack resonance frequencies by measuring the electro-mechanical impedance of the bonded piezoelectric wafer active sensor (PWAS). Based on the developed method, the bonded PWAS was used to excite the test plate at a high frequency utilizing a linear sine wave chirp from 1 to 500 kHz. The SLDV was used to acquire the dynamic response of each scanning area point. The crack resonance frequencies and corresponding operational vibration shapes were extracted from SLDV measurements to detect and visualize the interesting fatigue crack. The result showed the frequency spectrum of SLDV measurements and corresponding operation vibration shapes have much information about the tested crack compared with the E/M impedance spectrum. Gathering the experimental and finite element modeling results shows good potential for accurately assessing structural damage.
Carbon fiber reinforced polymer (CFRP) is an engineering composite material with excellent performance. After metallization, the CFRP composite exhibits unique properties such as electromagnetic shielding and high electrical conductivity. In this study, we utilized laser treatment process to enhance the adhesion strength of the copper layer electrolessed on CFRP composite. The surface microstructure of CFRP and the copper layer was determined using an optical microscope, and the adhesion force of the copper layer on CFRP composite was measured through 3M tape and pull-out tests. The results indicate that with an increase in the number of laser treatment cycles, the trenches depth on the surface of CFRP composite also increases, leading to high surface roughness and thus enhancing the adhesion strength between the copper layer and the composite. The adhesion state of the copper layer on laser-treated CFRP composite can be qualitatively classified as grade 5B. Additionally, both mechanical cutting and laser treatment can improve the adhesion strength of the samples. The samples treated by mechanical cutting and the laser scan with ±45° exhibit the highest adhesion strength of 5.48 MPa. This is 415 % higher than that of the untreated sample, with a minimum damage area after pull-out testing, approximately 10 %. Compared to the sandblasting pretreatment process, the adhesion strength of the sample by laser treatment increased by 119 %.
Polymers are one of the most important types of engineering materials used with reinforcing fibers in various industries in order to improve the mechanical properties. One of the most widely used composites is the carbon fiber reinforced plastic owning excellent mechanical properties such as high specific stiffness and specific strength. The fatigue performances imposed by standards have to be performed by means of experimental campaigns in laboratory on specimens. Classical procedures to evaluate the fatigue limit of material involve expensive and time-consuming tests because of the high number of specimens being tested. In the last decades, with an aim to reduce testing times and costs of fatigue tests, different techniques and methods have been proposed in order to study the various damage phenomena rapidly and consistently. Infrared thermography is considered as a promising method to investigate the fatigue behavior focusing on the metals and fiber reinforced plastic. The identification procedure of this method is based on the use of self-heating measurements and validate by comparing the prediction of the S-N curves given by the model and experimental fatigue results. In this study the thermographic technique based on surface temperature variation was used to assess the fatigue behavior of carbon fiber reinforced epoxy. To fabricate the composite samples, four layers of woven carbon fibers with an equal weight ratio of epoxy resin were used. The quasi-static tensile tests were conducted to determine the stress levels in classical and self-heating fatigue tests. The loadcontrolled fatigue tests were conducted with a stress ratio of 0.1 and loading frequency of 10 Hz. In fiber reinforced epoxy under cyclic loading the main mechanisms causing energy dissipation are attributed to the matrix cracking, fibers fracture, and interface cracking/friction among others. According to the fatigue tests analysis (evolution of the hysteresis area and Young's modulus) and the results obtained from self-heating tests, the energy dissipation mechanisms were discussed. It is worth noting that the obtained results from self-heating measurements can propose a good agreement with those attained by the classical methods. In other words an empirical relation could be considered between self-heating and classical fatigue results. Moreover with comparing the dissipated energies and stabilized temperatures in the self-heating measurements, there was a direct relation between them. Finite element simulation using commercially available ABAQUS software was also performed to model the temperature variations in the specimens subjected to cyclic loadings.
Electrically conductive polymer composites (CPCs) have been applied extensively in many fields such as electronics, wearable sensors and antistatic agent. It is still challenging to develop CPCs with a low percolation threshold and high electrical conductivity. Here, highly electrically conductive polystyrene (PS) composite with a fiber-based segregated structure is prepared by carbon nanotubes (CNTs) decoration onto the electrospun PS fibers, followed by hot press at a proper temperature. In the electrically conductive PS composite, the CNTs are segregated at the interface among the fiber-shaped matrix, and the one-dimensional fiber possessing the merit of a large aspect ratio, which facilitates the formation of conductive network. The percolation threshold is calculated to be 0.084 vol%, and the electrical conductivity of the CPC reaches 83.3 S/m when the concentration of the CNTs is 1.5 vol%. If the hot press temperature is much higher than the glass transition temperature of PS, the fiber-based segregated structure would be destroyed, increasing the percolation threshold while decreasing the conductivity of the composite. The fiber-based segregated structure provides a new and versatile route for the rational design and preparation of CPCs with a low percolation threshold and high conductivity.
For several decades, forming blend and composite of polyaniline (PANI) with insulating polymers has been a widely studied research area because of the potential applications of such blends, which have a unique combination of mechanical properties, the processability of conventional polymers and the electrical property of conducting polymers. The current review paper will emphasize PANI composites or blends with thermosetting polymer matrices. The enhanced electro-mechanical properties of the blends and composites depend on the uniform dispersion of the PANI particle in polymer matrix. Therefore, considerable studies have focused on improving the distribution of PANI particles within the thermoset matrices. In this review paper, all the parameters and conditions that influence the surface morphology and application of PANI thermoset blends and composites will be described systematically. Recent progress on PANI based thermoset system with multifunctional ternary composites research will be highlighted in this paper. Furthermore, encouraging applications of different PANI thermoset composites and blends are discussed, such as flame-retardant materials, lightning damage suppression, metal ion removal, anticorrosive coating, electromagnetic shielding, conductive adhesives, and sensing materials.
To date, the predictive analysis of lightning-induced damage of carbon fiber reinforced polymer composites (CFRP) is challenging due to the complex multi-physical coupling effects. The current study aims to clarify the lightning-induced damage mechanism of CFRP and improve the lightning protection systems for aerospace applications. Herein, an artificial lightning strike experiment was designed to simulate the real-life conditions and investigate the influence of lightning strike on a quasi-isotropic CFRP sample. The lightning strike and corresponding degradation process were observed by using a high-speed camera and infrared thermal imaging. Moreover, lightning-induced damage was assessed by visual inspection and non-destructive testing. The damage behavior of CFRP composites was deduced by analyzing the lightning process and damage modes. The results reveal that the damage is caused by the electro-thermo-mechanical response due to lightning arc flow and Joule heating ablation due to the conductive nature of the CFRP composites. The current work provides an enhanced understanding of the failure mechanism under lightning strike and outlines instructional suggestions to refine the numerical model of lightning-induced damage of CFRP for further study.
In this paper, the anticipated challenges and future applications of self-healing composite materials are outlined. The progress made, from the classical literature to the most recent approaches, is summarized as follows: general history of current self-healing engineering materials, self-healing of structural composite materials, and self-healing under extreme conditions. Finally, the next stage of research on self-healing composites is discussed.
The smart sensor is an effective way to detect damage and improve structural safety in structural health monitoring. Microcapsule‐based visualization sensors stand out from the smart sensors. Here, the research progress of microcapsule visualization materials in recent years is summarized and the sensing principles, influence factors, performances, applications, and future prospects are introduced. The way to achieve the visualizing function of microcapsule visualization sensors is the fabrication of microcapsules that are encapsulated with solutions of dyes or indicator. When the protective shell of microcapsules is broken, the dyes will be released and activated under optical, chemical, or mechanical conditions. These visualized microcapsules can be added to the interior of the structure or prepared as a coating to provide structural health monitoring of the interior and surface of the structure. They can accurately detect microcracks and highlight them in bright colors. Additionally, the structural health monitoring applications of microcapsule visualization sensing coatings in concrete, asphalt, and steel are presented with detailed examples. The development and application of these microcapsule visualization sensors are of great significance in improving the structural life and avoiding structural failure in engineering.
The influence of the microstructure of carbon fibre reinforced polymers (CFRPs) with epoxy matrix (E-CFRP) and nylon matrix (T-CFRP) on the galvanic behaviour of DP590 steel, 6022-aluminium alloy, 1040-steel and AZ31-magnesium alloy was investigated in the GMW14872 solution. The E-CFRP/metal couples were initially more galvanic corrosion resistant, but their galvanic corrosion gradually became more severe than the T-CFRP/metal couples. The effective micro-defects in the surface polymer layer of the CFRP samples critically determined the galvanic corrosion. A detailed surface layer model was proposed, the electrochemical processes through the surface polymer layers during galvanic corrosion were discussed. A better understanding on the microstructure of CFRP determined by composites manufacture process can be obtained. Keywords: Carbon fibre reinforced polymer (CFRP), Composite, EIS, Galvanic corrosion, Defect
In order to deeply reveal the microscopic damage mode and microscopic damage mechanism of Carbon Fiber Reinforced Plastic laminates (CFRP laminates) impacted vertically by the ice projectile at high velocity. In this paper, the loading system of the one-stage light gas gun, the liquid nitrogen circulating cooling system, the impact pressure measuring system and the high speed camera acquisition system are used, and the experiments of the spherical ice projectile (simulated hail ice, SHI) with diameter of 11 mm impacting CFRP laminates vertically at the velocity of 50-200 m/s were carried out. The impact pressure of the SHI impacting the target, the strain of X-Y in the two main directions at the impact point were measured, and the deflection/ time history curve at the impact point during the impact process was obtained. By using ABAQUS/Explicit finite element software, the numerical simulation of high-velocity vertical impact of SHI on CFRP laminates was compared with the image acquisition results of the high speed camera at different moments during the impact process, and the failure morphology and process of SHI was analyzed. At the same time, the delamination of the target obtained by numerical simulation is compared with the cracking of the CFRP fiber reinforcement and the delamination of the epoxy resin interface obtained by microscopic SEM observation, the correctness of using cohesion model to describe the micro-damage of CFRP laminates induced by SHI impacting vertically at high speed was verified. The damage failure threshold of CFRP laminates under the impact load of SHI under given experimental conditions was obtained. By establishing a three-point simply supported physical model, the ultimate deflection of laminated plates subjected to delamination failure was analyzed. Based on the measurement of strain and deflection at impact point, the valuable reference for the prediction of delamination failure in CFRP laminates can be provided, then the detection of the micro-damage to the surface composite part of the aircraft will be realized by the control of the sensor. Keywords: CFRP laminates, Cohesion model of ice projectiles, Microscopic damage model, Microscopic damage mechanism, Delamination failure prediction
This paper presents a detailed experimental investigation on the effects of projectile hardness on the behaviour of thermoplastic composites under impact loading. In this research, gas gun experiments employ gelatine and high-density polyethylene (HDPE) projectiles, of the same mass, to impact against woven carbon-fibre reinforced poly (ether-ether ketone) (CF/PEEK) composite specimens. During the experiments, a high-speed camera is employed to capture the deformation of the projectiles and a three-dimensional (3D) Digital Image Correlation (DIC) system is employed to record the deformation of the thermoplastic composite specimens. Experimental results are obtained from the composite specimens, impacted using gelatine and high-density polyethylene (HDPE) cylindrical projectiles with the same contact area. These results are compared to show the influence of projectile hardness on the impact response.
Purpose
This study aims to propose a simple experimental method to distinguish the galvanic corrosion, crevice corrosion and self-corrosion in metal/carbon fiber reinforced polymer (CFRP) joints.
Design/methodology/approach
The corrosion behaviors of four different galvanic couples, whose anodes were Zn-coated DP590 steel and Al 6022, and cathodes were two kinds of CFRP, were investigated in immersion and GMW14872 cyclic conditions.
Findings
The results showed that the galvanic corrosion caused by direct contact between CFRP and metals was more serious than that caused by the jointing bolts. The corrosion damage caused by crevice corrosion was severer than that caused by galvanic corrosion. Self-corrosion was also significant, particularly under the cyclic salt spray condition.
Practical implications
Cyclic salt spray test may more reliably simulate the galvanic corrosion of a joint in industrial service environments, and real corrosion damage may be underestimated by a galvanic current measurement.
Originality/value
A deeper understanding of different corrosion mechanisms involved in CFRP/metal joints under different service conditions in industry has been given.
This paper investigated which component of a lightning strike is responsible for the majority of damage in Carbon Fiber Reinforced Plastic (CFRP) by investigating the strength loss induced by the exposure to two different electric current waveforms. The two waveforms used were the 10/350µs waveform simulating the first return stroke during a direct strike according to IEC 61400-24 Ed1.0 and the second was a unipolar long stroke component. CFRP strip specimens were manufactured and subjected to the two waveforms of electric current to simulate a lightning strike event. After exposure, specimens were extracted from the CFRP strips, and then loaded in compression and shear to determine the residual strength remaining. The compression tests were conducted on uniaxial coupons and loaded in accordance to ASTM standard D6641. Shear tests were conducted on V-notch specimens and loaded in an Iosipescu test rig in accordance to ASTM standard D5379. The results of the tests were compared to CFRP coupons, which were not exposed to any electrical current. A comparison between undamaged specimens and damaged specimens was made to determine which has more effect on the strength degradation; electric charge from the long stroke component or specific energy from the first return stroke. The results show that impulse current has more impact on strength degradation than a unipolar long stroke current.
Machining damage occurs on the surface of carbon fiber reinforced polymer (CFRP) composites during processing. In the current simulation model of CFRP, the initial defects on the carbon fiber and the periodic random distribution of the reinforcement phase in the matrix are not considered in detail, which makes the characteristics of the cutting model significantly different from the actual processing conditions. In this paper, a novel three-phase model of carbon fiber/cyanate ester composites is proposed to simulate the machining damage of the composites. The periodic random distribution of the carbon fiber reinforced phase in the matrix was realized using a double perturbation algorithm. To achieve the stochastic distribution of the strength of a single carbon fiber, a novel method that combines the Weibull intensity distribution theory with the Monte Carlo method is presented. The mechanical properties of the cyanate matrix were characterized by fitting the stress-strain curves, and the cohesive zone model was employed to simulate the interface. Based on the model, the machining damage mechanism of the composites was revealed using finite element simulations and by conducting a theoretical analysis. Furthermore, the milling surfaces of the composites were observed using a scanning electron microscope, to verify the accuracy of the simulation results. In this study, the simulations and theoretical analysis of the carbon fiber/cyanate ester composite processing were carried out based on a novel three-phase model, which revealed the material failure and machining damage mechanism more accurately.
Carbon fiber reinforced plastic composites (CFRPs) possess superior elastic mechanical properties. However, CFRPs lack sufficient viscoelastic performance, such as damping and creep resistance. In an effort to improve these properties, in this study, hybrid multiscale composites with various combinations of zinc oxide nanorods (ZnO) and carbon nanotubes (CNTs) were deposited at the interface of carbon fiber laminae. The viscoelastic properties of the corresponding composites were characterized via dynamic mechanical analysis (DMA) during both temperature and frequency sweeps. The creep activation energy for each composite configuration was also calculated. The DMA temperature sweep analysis reported that the composite incorporating both ZnO and CNTs exhibited the highest improvements in all viscoelastic properties. This composite also attained better creep resistance, evident by the highest activation energy. The DMA frequency sweep analysis revealed that composites incorporating a single nanofiller improves the viscoelastic properties more than the combined nanofiller composite. Despite these improvements in the viscoelastic properties, the non-uniform dispersion and agglomerations of the nanofillers affected some of the elastic properties negatively, such as the storage modulus.
Composite materials are heterogeneous in nature and suffer from complex non-linear modes of failure, such as delamination, matrix crack, fiber-breakage, and voids, among others. The early detection of damage in composite structures, such as airplanes, is imperative to avoid catastrophic failure and tragic consequences. This paper reports on the use of machine learning techniques for the damage assessment (i.e., detection, quantification, and localization) of smart composite structures. The success of the machine learning paradigm for damage assessment depends on the representational capability of the discriminative features for the problems of interest. However, from a practical standpoint, it is not possible to define a global or superset of discriminative features that could discriminate between damaged and undamaged states of the structures, and simultaneously make a distinction between various modes of failures. In addition, one machine learning algorithm may show optimum performance for the discriminative features of a particular problem but fails for others. This article focuses on a review of discriminative features and the corresponding machine learning algorithms (both supervised and unsupervised), for various types of damage in smart composite structures.
Moisture diffusion in carbon fiber composites changes the mechanical properties of the composite. Therefore, a monitoring method of the actual content of moisture in the composite is important. However, at the moment there are no online methods established. A common method is the measurement of the mass changes due to water uptake. This method is not suitable for online monitoring of a real composite part in service. We demonstrate that miniaturized flexible interdigital sensors are suitable for moisture measurement inside the carbon fiber composite. These sensors are directly integrated inside the composite. It was already demonstrated that these can be successfully used for resin-curing monitoring as a primary application. Here we demonstrate that the same sensors are also suitable for moisture measurement inside the material. In order to do so, we expose samples with and without integrated sensors to hot-wet conditions and measure the dielectric changes with the sensors and the mass gain. The moisture concentration and the measured admittance can be directly correlated to each other. This demonstrates that the sensors can be used for moisture measurement as a secondary application. In addition, it is shown that the sensors have the potential to measure the moisture locally inside the material.
Inspired by biological systems, self‐healing coatings have been fabricated to protect metals against corrosion. However, in situ monitoring of the corrosion dynamics for various self‐healing strategies generally remains a big challenge due to different working mechanisms. In the present work, a universal intelligent‐sensing coating (SC) system containing pH‐responsive polymer microspheres with a color probe is developed. When corrosion occurs in the self‐healing system, the color around cracks turns pink gradually over time owing to the increased pH value. For the high‐performance self‐healing coatings, the onset and propagation of corrosion is suppressed, thereby leading to a narrow light‐pink‐color area. With this smart SC approach, the corrosion dynamics is established for three self‐healing strategies by the correlation between the width of color lines with time. The anticorrosion ability in 48 h for the three extrinsic self‐healing strategies are evaluated; that is, the SC with benzotriazole‐loaded poly(divinylbenzene)‐graft‐poly(divinylbenzene‐co‐acrylic acid) microspheres (PDVB‐graft‐P(DVB‐co‐AA)‐BTA) is superior to that with BTA‐loaded halloysite (Halloysite‐BTA), which surpasses that with polyurethane/poly(urea‐formaldehyde) microcapsules filled with isophorone diisocyanate (IPDI@PU/PUF). These results are consistent with electrochemical experiments. This smart‐sensing coating system can be a promising alternative for the in situ investigation of the anticorrosion performance of various self‐healing anticorrosion strategies.
There are many problems facing aircraft in the air during flight, such as lightning strikes and ice accumulation on aircraft surfaces. These problems usually reduce aircraft efficiency and lead to serious accidents and fatalities. However, the current protection systems used to solve these problems of aircraft represent excessive energy usage, a hazard to the environment, and they are generally bulky, heavy and costly. Therefore, there are new conductive composites containing an embedded layer of conductive fibers such as graphene and carbon nanotube designed to carry lightning currents, in addition to that, there is a new deicing heater element made of graphene nanoribbons films to be used in ice protection systems. This paper presents a review of some problems facing aircraft in the air, such as lightning and ice accumulation on the surfaces of the aircraft and the significant efforts that have been exerted to address and solve these issues. Also, this paper reviews the contribution of composite materials in reducing the weight of the aircraft and fuel consumption as well as increasing the efficiency of aircraft. This paper also will review the conductive composite materials and its application for aviation, in addition to their contribution to solving the most important problems in aviation.
Despite the recent advances in the field of manufacturing of composite materials, with both thermosetting and thermoplastic matrix, the presence of irregularities that influence their mechanical properties and behavior remains a critical issue to the industry. The defects with the form of porosity, fiber misalignment, delamination and poor consolidation are considered an unavoidable form of initial damage to composite materials. The reduction of the defects by optimizing the manufacturing process and the creation effective tools for predicting the residual properties of these materials during the design and/or the manufacturing phase are of great interest. In the present work, presented are these numerical tools and methodologies based either on the idea of optimizing the manufacturing process or by using data derived from non-destructive tests. Finally, the possibility of combining the two approaches is being proposed.
Poly(ether ether ketone) (PEEK), with its superb mechanical properties, excellent chemical resistance and high thermo-oxidative stability is one of the most important engineering thermoplastics for high-end applications. In this work, we investigate the elastic and viscoelastic properties along with the creep mitigation of two sets of samples: PEEK reinforced with graphene nanoplatelets (GNPs) and PEEK reinforced with a hybrid graphene/short carbon fibre (CF) filler. The melt viscosity of the PEEK nanocomposites was found to increase with increasing GNPs content; however, the viscosity of the hybrid CF-GNP samples with the highest filler content was equal to the one of the samples filled only with GNPs at low shear rates. This processability shows the advantage of GNPs over other nano and conventional fillers in the ability to use meaningful loadings. The introduction of GNPs improved significantly the stiffness and the storage modulus of the materials in both PEEK-GNP and PEEK-CF-GNP composites. Moreover, the presence of GNPs within the composites led to a restriction of the mobility of the macromolecular chains of PEEK, which resulted in enhanced creep properties at both room temperature and elevated temperatures. Overall, the nanocomposites produced displayed properties that make them attractive in applications where high stiffness and structural integrity at elevated temperatures are required.
Composite materials such as glass and carbon fibre composites have become popular and the preferred choice in various applications due to their many advantages such as corrosion resistance, design flexibility, high strength and light weight. Combining materials with different mechanical properties make composites more difficult to evaluate where the damage mechanisms for composites are more complex than traditional materials such as steel. A relatively new non-destructive testing (NDT) method known as the electromechanical impedance (EMI) technique has been studied by various researchers, but the damage detection performance of the method on composite structures still requires more investigations before it can be accepted for field application, especially in aerospace industry due to the high standard of safety. In this paper, the detection capabilities and performance of the EMI technique subjected to different PZT attachment methods have been investigated. To this end, glass fibre composite plates with various attachment methods for the sensor have been prepared and detection of common defects such as delamination and crack with the EMI technique under study has been performed. The performance of each attachment method for identifying different damage types has been analysed and finite element analysis (FEA) was carried out for verification of the experimental results.
Carbon is used as a reinforcing phase in carbon-fiber reinforced polymer composites employed in aeronautical and other technological applications. Under polarization in aqueous media, which can occur on galvanic coupling of carbon-fiber reinforced polymers (CFRP) with metals in multi-material structures, degradation of the composite occurs. These degradative processes are intimately linked with the electrically conductive nature and surface chemistry of carbon. This review highlights the potential corrosion challenges in multi-material combinations containing carbon-fiber reinforced polymers, the surface chemistry of carbon, its plausible effects on the electrochemical activity of carbon, and consequently the degradation processes on carbon-fiber reinforced polymers. The implications of the emerging use of conductive nano-fillers (carbon nanotubes and carbon nanofibers) in the modification of CFRPs on galvanically stimulated degradation of CFRP is accentuated. The problem of galvanic coupling of CFRP with selected metals is set into perspective, and insights on potential methods for mitigation and monitoring the degradative processes in these composites are highlighted.
Carbon fiber reinforced plastics (CFRPs) are vulnerable to lightning strikes due to their low electrical conductivity and low heat resistance. A lightning strike can damage CFRP structure catastrophically. Most common lightning strike protection (LSP) technology, consists of expanded metal foils/films on top of composite structures. This technology possesses disadvantages such as increased weight, galvanic corrosion, expensive integration and repair costs. In the present study, authors introduce a novel, easy to apply and all-polymeric LSP material. A doped intrinsic conductive polymer i.e. Polyaniline (PANI) dispersed in a thermosetting cross-linking polymer divinylbenzene (DVB) has been used to prepare an adhesive layer of 0.25–0.4 mm thickness. CFRP structure coated with PANI-based LSP layer, when tested against simulated lightning impulse current of 100 kA, demonstrated effective dissipation of the current, rendering almost 100% safety to the CFRP structure. PANI showed the capability to create a 3-D conductive network due to its self-assembling property, which makes it superior compared to its counterpart carbon/metal nano-filler based LSP technologies. Almost 100% residual strength of PANI-LSP protected CFRPs is reported in this work.
Within decades of development, carbon nanomaterials such as carbon black, fullerene, carbon nanotube, carbon nanofiber, graphene and their combined nanofillers have been tremendously applied in polymer material industries, generating a series of fascinating multifunctional composites in the fields from portable electronic devices, sports, entertainments to automobile, aerospace and military. Among the various material properties of the composites, electrical conductivity and mechanical performance are the two most important parameters for evaluating the effectiveness of nanofillers in the polymer matrices. In this review, we focus on the electrical and mechanical properties of diverse dimensional carbon nanofillers (e.g., zero-, one-, two-, three-dimensional nanofillers or their combinations)-reinforced polymer composites to seek the most efficient and effective approach to obtain high-performance polymeric nanocomposites.
Plastic matrix composite materials are an excellent choice for structural applications where high strength-weight and stiffness-weight ratios are required. These materials are being increasingly used in diverse industrial sectors, particularly in aerospace. Due to the strict tolerances required, they are usually machined with drilling cycles due to the type of mounting through rivets. In this sense, laser beam drilling is presented as an alternative to conventional drilling due to the absence of tool wear, cutting forces, or vibrations during the cutting process. However, the process carries with it other problems that compromise the integrity of the material. One of these is caused by the high temperatures generated during the interaction between the laser and the material. In this work, variance analysis is used to study the influence of scanning speed and frequency on macro geometric parameters, surface quality, and defects (taper and heat affected zone). Also, in order to identify problems in the wall of the drill, stereoscopic optical microscopy (SOM) and scanning electron microscopy (SEM) techniques are used. This experimental procedure reveals the conditions that minimize deviations, defects, and damage in machining holes.
This research study reports the creep behavior analysis of the new composite materials manufactured by 3D printing technology. Nylon was used as a polymer matrix, and carbon fiber, Kevlar, and fiberglass were used as reinforcing agents. Since the properties of 3D-printed components are usually insufficient for robust engineering applications, adding reinforcing fibers improves the performance of these components for several engineering applications. Fiber-reinforced additive manufacturing (FRAM) is an almost 4-year-old technology. Additionally, there is not sufficient research on the behavior of FRAM components specifically at high temperatures. Therefore, the investigation of the high-temperature behavioral analysis of FRAM components was focused on in this study. Creep properties of the composite specimens reinforced by different fibers were measured by the dynamic mechanical thermal analysis system. The statistical analyses were conducted to analyze the experimental data using mathematical models. The microstructural analysis was performed to further investigate parts’ morphology, 3D printing quality, and fracture mechanisms. The results indicated that the creep compliance of reinforced composite specimens was significantly improved in comparison with pure nylon. Overall, this paper presents quantitative creep analysis results demonstrating the capabilities of FRAM components to be used for several engineering applications.
Abstract Over the last two decades, the repair of existing engineering structures using fiber reinforced polymer composites has attracted a great attention by aerospace industry, as it is more economical than replacing new. With an increased use of composite material in aerospace field, it is thus essential to restore the structural integrity by repair of damaged part. Concerns regarding the long term durability of composite repair bonded joints have been a major obstacle for critical component of aerospace structures. This paper reviews the current research on the environmental durability of adhesive bonded repair of composite structures to focus on the durability concerns and suggestion on the research needed in this area. The most important environmental factors (moisture and temperature) are reviewed thoroughly and also combined environmental effect. Finite element methods used to predict the environmental influence on the composite bonded joints are briefly reviewed. Finally, the paper concludes with key findings, opportunities and future research topics in order to develop cost effective, better quality and reliable composite repair bonded joints.
Carbon fiber reinforced epoxy and nylon were measured by means of potentiodynamic polarization, potentiostatic polarization and AC electrochemical impedance spectroscopy (EIS) in a solution containing 0.9wt% NaCl, 0.1wt% CaCl2 and 0.075wt% NaHCO3. Their microstructures were examined by SEM. The results showed that these two types of carbon fiber reinforced polymers (CFRPs) were electrically conductive and electrochemically noble, and exhibited different EIS characteristics. Strong anodic and cathodic polarization could damage their surface polymer layers. Based on their different microstructures and electrochemical behaviors, a surface polymer layer model was proposed for these CFRPs.
The birth of smart materials such as piezoelectric (PZT) transducers has aided in revolutionizing the field of structural health monitoring (SHM) based on non-destructive testing (NDT) methods. While a relatively new NDT method known as the electromechanical (EMI) technique has been investigated for more than two decades, there are still various problems that must be solved before it is applied to real structures. The technique, which has a significant potential to contribute to the creation of one of the most effective SHM systems, involves the use of a single PZT for exciting and sensing of the host structure. In this paper, studies applied for the past decade related to the EMI technique have been reviewed to understand its trend. In addition, new concepts and ideas proposed by various authors are also surveyed, and the paper concludes with a discussion of the potential directions for future works.
In this research, the effects of multi-walled carbon nanotubes on the distribution of long-term creep strains in thick-walled multi-walled carbon nanotube/fiber/polymer three-phase laminated composites are studied. In the first step, micromechanical models are developed to calculate the elastic properties of multi-walled carbon nanotube/vinylester and multi-walled carbon nanotube/E-glass fiber/vinylester composites. Using classical lamination plate theory, equilibrium and compatibility equations and strain–displacement relations, the distribution of effective stresses is considered. Moreover, utilizing Schapery single-integral model for nonlinear viscoelastic materials, Prandtl–Reuss relations and Mendelson’s approximation method, not only the distribution of circumferential and radial strains is investigated but also the effects of fiber orientation and weight fraction (wt.%) of the multi-walled carbon nanotubes on the way of distribution are studied. The results demonstrated that the addition of the multi-walled carbon nanotube to the vinylester can reduce absolute values of the radial and circumferential creep strains and dimensionless effective stresses. Moreover, most reduction occurred in the inner wall of the cylindrical shell when fiber orientation was α = 90°.
A large amount of electrically conductive fillers is needed to enhance a Carbon Fiber Reinforced Plastics (CFRP) electrical conductivity enough to withstand lightning strikes of peak currents. However, such large alien constituents hamper the inherent good mechanical properties of CFRP structures. In this work, a solution has been proposed to retain both desired properties in a CFRP laminate. Layer-wise hybrid laminate has been demonstrated as a solution for lightning strike protection of Carbon Fiber Reinforced Plastics (CFRP). Top few layers of a hybrid laminate are prepared using electrically conductive polymer-based resin (CF/C-POLY) to provide effective dissipation of lightning current while epoxy-based CFRP substrate (CF/Epoxy) provides the main structural strength. An insulating adhesive layer is used to bond CF/C-POLY and CF/Epoxy to prepare the laminate. The hybrid laminates were tested for their effectiveness against lightning strikes. Laminates were struck by modified lightning waveform of component A with peak current of -14 kA and -40 kA. The performance of the laminates against lightning strike were evaluated using high speed camera, high-speed and thermal camera. It is found that CF/C-POLY layer successfully defended the main structural component i.e. CF/Epoxy from lightning direct damage.
Carbon fiber reinforced polymer composites are widely used in aircraft structures due to their excellent mechanical properties, light weight, and corrosion resistance compared to conventional metallic materials. However, the low electrical conductivity in the composite’s thickness direction makes them susceptible to lightning strike damage. An all-polymeric lightning strike protection (LSP) system based on a conductive polymer (polyaniline) adhesive layer has been proposed in recent literature. A preliminary study suggests the polyaniline-based adhesive layer has good electrical conductivity, low density, easy applicability, and corrosion resistance, which make it a strong contender for a next-generation LSP solution. However, being a novel technology with a low technical readiness level, its impact on the aircraft weight, cost, and performance remains unknown. In this work, technology impact forecasting has been deployed for the first time to explore the potential impact of the novel LSP technology in the context of a commercial aircraft system. This work presents a rapid assessment on the feasibility and economic viability of the novel LSP technology, and the results have been compared with the traditional metal mesh and the more widely used expanded metal foil LSP technologies. The results from this study show that, although the parasitic weight of the conductive polymer is lower than that of the metal mesh, the expanded metal foil is still a better option in terms of weight savings. From the economic perspective, the proposed new technology could lead to greater profitability in research, development, testing, and evaluation cost. However, this is compromised by the increased costs in the manufacturing and maintenance of such new material technology.
Investigations of the fatigue performance of composite materials have accompanied their introduction in several engineering domains since the 1950s. An abundance of publications have emerged dealing with the experimental investigation of the fatigue performance of composites under different loading and environmental conditions, as well as the development of theories for the modeling of the fatigue behavior and/or prediction of the fatigue life of the materials systems under consideration. This work aims to briefly review and present the history of fiber-reinforced polymer composite laminate fatigue investigations, dividing the last 70 years into three periods. The early 1950–1975 period, when the “new” materials and their behavior under (simple) fatigue loading patterns were discovered. The mature, 1975–2000 period, when more loading and material parameters were investigated and the basic theoretical background was established. And finally, the later period, in the new millennium, when more detailed experimental campaigns were performed (assisted by developments in a multitude of engineering and scientific fields) and parameters that had previously been overlooked by researchers were taken into account.
Continuous carbon fiber carbon-matrix (C/C) and polymer-matrix (CFRP) structural composites without poling are electrets. Their DC electric field E (hence the volumetric power density Pv for structural self-powering) increases linearly with increasing inter-electrode distance l (more significantly for C/C). Short-circuit discharge and open-circuit self-charge occur reversibly. The fraction of carriers that participate is 1.6 × 10⁻³ and 2.8 × 10⁻³ for CFRP and C/C, respectively. At l = 140 mm, E = 1.2 × 10⁻⁴ V/m, and Pv is 5.0 × 10⁻⁵ and 2.5 × 10⁻⁴ W/m³ for CFRP and C/C, respectively. The participating carrier density is 2.4 × 10²¹ and 2.6 × 10²² m⁻³, and the discharge time per unit participating charge is 6.7 × 10⁶ and 8.9 × 10⁴ s/C for CFRP and C/C, respectively. The C/C gives higher power density, whereas CFRP discharges more slowly. The polarization-induced apparent resistance increase upon DC current polarity reversal is asymmetrical. Elastic tension affects E, relative permittivity κ and resistivity ρ essentially reversibly and linearly (more significantly for C/C), enabling piezoelectret/piezoresistive self-sensing and piezoelectret-based energy harvesting. The strain causes CFRP to increase in E, κ and ρ, and C/C to decrease in E and ρ and increase in κ. Increasing the temperature from 20 °C to 70 °C increases E reversibly by 1900% and increases the volumetric power density by 40000%, as shown for C/C.
Polymeric materials are susceptible to small damage which is undetectable. Without timely and effective repair treatment, the damage may deteriorate the integrity of materials and ultimately result in the material failure and catastrophe. Autonomous warning and repairing the damage simultaneously is of great practical significance yet difficult to realize. Herein, we introduce a smart coating with autonomous warning of and repairing damage by simple incorporating nanosensors embedded with phenanthroline as a corrosion indicator and inhibitor. The electrochemical corrosion resulting from coating damage can be rapidly warned by a prominent orange red color in just five minutes. Accompanied with the warning function, the smart coating exhibits efficient repairing performance on defected region, as reflected from the disappearance of electrochemical admittance peak. This simple and powerful strategy dependent on single active component to achieve autonomous warning and repairing effect is highly expected to provide a new avenue for enhancing the security and longevity of other polymeric materials.
FMLs are laminate structures that consist of alternating layers of metal and composite and are designed to achieve certain properties that exceed those of either constituent individually. The possibility of galvanic corrosion typically prohibits the pairing of carbon fibre and aluminium in a fibre metal laminate. Despite all of the excellent properties of CFRCs, there are issues with using CFRC and metals together. Carbon fibres in CFRPs cause this material to become electrically conductive. The carbon fibres are electrically conductive and electrochemically very noble Therefore, when a metal is electrically connected to a CFRP, it is more susceptible to galvanic corrosion. This situation becomes worse when a large surface area of carbon composite components is coupled to small metallic parts (such as fasteners, bolts and nuts). In these circumstances, the rate of galvanic corrosion is extremely high due to the high cathode. In this present work, study the corrosion behaviour of CFRP type FML and control by the green corrosion inhibitors. These inhibitors could also be extended to dissimilar metal joints made by other fabrication techniques.
Effects of salt fog on CFRP-steel bonded joints were studied via simulation by accelerated cycles. CFRP-to-steel double strap joints made of two different types of laminates were subjected to salt fog cycles for 5000 h and Mode-II tests conducted to assess the degradation of their bond capacity at selected time stages of the process. Different mechanisms causing strength losses were found and analyzed. Results showed that the bond capacity of joints increased initially but was reduced at later stages. Corrosion debonding took place in the chamber between 5,000 h and 10,000 h prior to the application of external loading. Combined Attenuated Total Reflectance- Fourier transform infrared (FTIR) spectroscopy and Dynamic Mechanical Analysis (DMA) results showed that severe degradation at the interface of carbon fibers and resin only took place for one type of laminate. Galvanic corrosion was also analyzed and coupling between CFRP and steel developed due to the corrosion product depositions over the components leading to the degradation of the same type of laminate.
In this research a reduced graphene oxide (rGO) is used to coat the carbon fiber reinforced epoxy composite (CFRE) to improve and enhance its electrical conductivity that can be used in the aviation applications, because CFRE has poor electrical conductivity, and cannot withstand high electrical current coming from lightning strike. The results show that the electrical conductivity of CFRE is enhanced and increased significantly when it is coated with rGO by about 8015%, where the electrical conductivity of CFRE is increased from 1.38 × 10 ³ (S/m) to 1.12 × 10 ⁵ (S/m). Also when the content of rGO increased, the electrical conductivity of CFRE neat will be increased to higher values. The self-heating of all tested specimens was analyzed by the Joule effect. It is found that the self-heating of CFRE is enhanced and improved after coating it with rGO, therefore the self- heating of CFRE become more homogeneous, effective, reaching higher temperatures, than CFRE neat.
Polymers are susceptible to small damages which are difficult to be detected and repaired, and may lead to catastrophic failure if left unattended at their early stage. How to autonomously warn and repair them simultaneously is promising yet challenging, owing to difficulty in integrating different functional elements for packaging and lack of suitable vehicles to carry a multi-role trigger with high reactivity. Herein, inspired by human skin in damage-healing process, we report a genuinely fully autonomous smart material that is capable of warning and healing damages via simply incorporating dual microcapsules containing polyamine as a multi-role trigger and epoxy monomer dyed with a pH indicator, respectively. Both microscopic ‘subcutaneous’ damages and macroscopic surface damages can be warned by conspicuous red color, not only rapidly upon their occurrence, but also permanently after being repaired. Accompanied with the comprehensive warning, the smart material shows high healing performance upon dynamic impact damages with efficiency up to 100% without any external interventions. This facile and ready strategy with fully autonomous warning and healing functions independent of host matrix provides a new avenue to enhance the reliability and longevity of a wide variety of polymeric materials ranging from functional coatings to structural composites.
The work aims to investigate the capability of a vertical tail leading edge to withstand bird strike and to provide general considerations on the improvement of such capability with respect to the mass saving and to the required structural performances by considering different material systems. The assessment of the numerical models was ensured by a double check, and therefore considering the two test cases, aimed to calibrate and validate the numerical models against experimental data, coming from literature: 1) bird strike on metallic flat square plate; 2) bird strike on wing leading-edge with the skin made in metallic sandwich structure (both the honeycomb core and the outer and inner face was in aluminum). Finally, the crashworthy design of several leading-edge configurations, modifying the material and thickness of the skins and the central core of the leading edge, without changing its external geometrical shape, was investigated by adopting the numerical procedures used for the validation test cases. Actually, unidirectional fiber-reinforced composite material systems were considered for the outer and inner face of the skins, while different materials were adopted for the core. A comparison among the developed configurations, in terms of requirement fulfillment, global deformation parameters and weight, was performed.
Engineering structures are often subjected to the conditions of cyclic-loading, which onsets material fatigue, detrimentally affecting the service-life and damage tolerance of components and joints. Carbon fibre reinforced plastics (CFRP) are high-strength, low-weight composites that are gaining ubiquity in place of metals and glass fibre reinforced plastics (GFRP) not only due to their outstanding strength-to-weight properties, but also because carbon fibres are relatively inert to environmental degradation and as such, show potential as corrosion resistant materials. The effects of cyclic loading on the fatigue of CFRP are detailed in several papers. As such, collating research on CFRP fatigue into a single document is a worthwhile exercise, as it will benefit the engineering-readership interested in designing fatigue resistant structures and components using CFRP. This review article aims to provide the most relevant and up-to-date information on the fatigue of CFRP. The review focuses in particular on defining fatigue and the mechanics of cyclically-loaded composites, elucidating the fatigue response and fatigue properties of CFRP in different forms, discussing the importance of environmental factors on the fatigue performance and service-life, and summarising the different approaches taken to modelling fatigue in CFRP.
Phenolic resin was mixed with a cross-linking agent divinylbenzene (DVB) to prepare a polyaniline-based electrically-conductive thermosetting polymer composite. It has been shown that this Phenol-DVB mixture can undergo cationic polymerization in the presence of the dodecylbenzene sulfonic acid (DBSA)-doped polyaniline (PANI). Composites with different weight ratios of phenolic resin and DVB were mixed with a fixed weight of DBSA-PANI (i.e. 30 wt. %). Increasing the phenol content in the resin system was found to improve the electrical conductivity of the composite to almost 2700%. This improvement has been assigned to the reduced de-doping of polyaniline in phenol-DVB resin. Active sites of phenol effectively attached to the β carbon of DVB and reduced the proton subtracting species of DVB, leading to reduced de-doping of PANI. This behavior was studied through various characterization techniques including differential scanning calorimetry (DSC), FT-IR spectro-scopy and Scanning Electron Microscopy (SEM). Electrical conductivity measurement, mechanical properties, and in-situ electrical conductivity measurements were performed to find the optimized properties of the composite. Optimized composites prepared with the composition of 30 wt. % DBSA-PANI and 70 wt. % of phenol-DVB (50 wt. % each), have shown electrical conductivity of 0.20 S/cm and a flexural modulus of 2.1 GPa, which is a significant improvement in the flexural properties of polymer based-thermosetting composites with similar electrical conductivity. This material can be a potential candidate for the lightning strike protection of fiber reinforced plastics.
Suppression of electrochemical activity (cathodic activity) on CFRP surface at cathodic potentials consistent with galvanic coupling of CFRP with active metals like aluminium and zinc have been demonstrated by electrochemical treatment of CFRP surface in the presence of sodium dodecyl sulphate (SDS). Modification to the CFRP surface by SDS adsorption was established using electrochemical impedance spectroscopy, cyclic voltammetry, and confocal Raman spectroscopy and atomic force microscopy. Electrochemical test results indicate interaction of SDS with CFRP with persistent effects, manifesting in a sustained suppression of electrochemical activity even after washing the treated CFRP surface. Mitigation of CFRP degradation under cathodic polarization in the presence of SDS and/or after prior exposure to SDS was established from scanning electron microscopy. Based on results obtained herein, plausible mechanisms/configurations involved in SDS interaction(s) with carbon fibre surfaces of the CFRP composite (that most probably account for reduced cathodic activity) were postulated.
Carbon fiber reinforced composites are very much imperative to future-generation aircraft structures. However, lightning strike protection (LSP) and electromagnetic interference (EMI) are main concerns. Carbon fibers have very good mechanical properties with the best strength-to-weight ratio, but they are very poor conductors of electricity. These fibers must be reinvented to increase the surface conductance to provide high electrical conductivity to the aircraft structure. The present study deals with preparing composite sandwich structures of carbon fibers used for commercial nacelle applications subject to lightning strike effects with different metallic nanofilm of gold (Au) and silver (Ag) measuring approximately 100 nm. These metallic nanofibers were co-cured on the top layers of composite panels during vacuum curing process. In our laboratory, lightning strike results for a composite sandwich structure using nanofilms were obtained to observe lightning strike damage and structural tolerance necessary to observe the damage tolerance capability. Resistance of composite panels with metallic nanofilm under various strains was studied. It was found that resistance of the metallic nanofilm increased under strain. The voltage was found to be low; hence, an increase in current would help to reduce the damage on composite panels due to lightning strikes, and the same theory would be applicable to EMI. No EMI was absorbed or reflected in the nanofilm using the P-static test. When lightning strikes were applied to composite coupons, the resulting damage from the currents was reduced on those with metallic nanofilms.
This paper reviews multifunctional structural materials, particularly continuous fiber polymer-matrix composites. The non-structural functions include sensing, EMI shielding, heating, energy generation, energy storage, actuation and self-healing. For each function, the materials, composite design, functional performance and relevant technological needs are covered. Both unmodified and modified forms of the composite are addressed. Sensing, EMI shielding, heating and actuation are functions that do not require modification, though modifications can be performed. In contrast, energy generation, energy storage and self-healing require modification. For a continuous fiber polymer-matrix composite, the modification commonly involves the incorporation of constituents at the interlaminar interface.
The homogeneous dispersion of carbon nanotubes, (CNTs), in a cementitious matrix is a crucial procedure that affects both mechanical properties and electrical conductivity of the nanocomposite. Electrochemical Impedance Spectroscopy, (EIS), can be very useful in studying and characterizing the impact of the CNT content in nanoreinforced cementitious materials in a quantitative way. In this study, measurements of the resistance, reactance and capacitance reveal the nature of circuit elements formed by the nanotube network in cement mortars reinforced with various amounts of carbon nanotubes and provide insight of the nanotubes’ dispersion state. Resistivity results show that percolation threshold was reached between CNT weight fractions of 0.1% and 0.15 wt%. Below percolation, a consistency between resistive and capacitive phases exists, i.e., resistivity, reactance and capacitance were found to decrease as the nanotube content increases. After the continuous conductive network was formed, and percolative behavior was achieved, resistivity values show a little dependence on the CNT content. However, the presence of CNT entanglements was found to contribute to an amplified energy storage ability, as both the imaginary part of impedance (reactance) and capacitance were increased. A correlation between capacitance, flexural strength and modulus of elasticity was observed for the first time. Capacitance values provide valuable information on the energy storage ability of the material and how the actual CNT dispersion state affects the mechanical properties of percolative nanoreinforced cementitious materials. Finally, a general micromechanics model, modified by taking into account the conductive mechanisms below and above percolation threshold, was successfully implemented. The theoretically determined values of the overall electrical conductivity are in good agreement with the experimental results.
Nanocontainers with controlled release properties have been used in self-healing coatings for many years. However, the spontaneous leakage of the small molecular weight inhibitors from the nanocontainers promoted the development of nanovalves or gatekeepers to control inhibitor release. Herein, we demonstrate a facile method to encapsulate corrosion inhibitor in mesoporous silica nanoparticles (MSNs) with the help of tannic acid complexes, which endow the inhibitor loaded MSNs with pH-controlled release function. Commercial water-borne alkyd coating impregnated with 2 wt% of benzotriazole-loaded nanocontainers presented significant self-healing effect after 20 days of immersion in 0.1 M NaCl solution from both released benzotriazole and tannic acid as confirmed by electrochemical impedance spectroscopy and microscopy. The impedance modulus of coating with nanocontainers increased from 4.7 × 10⁴ Ω cm² to 1.8 × 10⁵ Ω cm² after 15 days of immersion.
The lightning damage resistance of Pultruded Rod Stitched Efficient Unitized Structure
(PRSEUS) panels was characterized experimentally. Two unprotected PRSEUS panels were
subjected to standard impulse current waveforms (consistent with actual lightning strikes) with
50, 125, and 200 kA nominal peak currents at a variety of panel locations. Lightning-induced
damage to the PRSEUS panels was a strong function of (1) the peak current, (2) the lightning
attachment location (mid-bay, stringer, frame, etc.) that involved different through-thickness
Vectran™ stitching, and (3) the presence of a surface finish paint.
The sizes of the damaged regions increased as the peak current increased, since greater peak
current leads to more Joule heating. The lightning-damaged PRSEUS panels exhibited unique
damage features due to the presence of through-thickness Vectran™ stitches and warp-knitted
fabrics. Through-thickness Vectran™ stitches constrained the development and spread of intense
local damage in the vicinity of the lightning attachment point. The polyester warp-knit threads
used to stitch the warp-knitted laminates together appeared to influence the development of
widespread small-scale fiber damage in the region surrounding the strike. Consequently, the
Vectran™ structural stitches, as well as the polyester knit threads holding the tows together, have
a significant beneficial effect on both the size of the impingement region and the subsequent
damage propagation within the laminate. In addition, damage to the painted panel was greater for
each current level than for the sanded (unpainted) panel.
Most common lightning strike protection (LSP) technology consists of expended metal foils/films on top of composite structures. This technology possesses disadvantages such as increased weight, galvanic corrosion, expensive integration and repair process. In the present study, authors showed an all-polymeric LSP technology and confirmed its effectiveness against lightning strike. Polyaniline is an intrinsic conductive polymers, which can be rendered conductive by doping with a strong acid. Dodecylebenzesulfonic acid is used as dopant for PANI in current work. Authors, prepared a thermosetting resin system, where, DBSA doped PANI complex (semi-doped) was mixed with divinylbenzene (DVB). This conductive resin system was used to impregnate glass fiber (GF) and carbon fiber (CF) to prepare conductive GFRP and CFRP laminate composites. Prepared composites were tested against simulated lightning strikes of 40 kA. Very limited visible damage was observed in both the cases.