Carbon Fiber Reinforced Plastic Substrate Research Articles

Pretreatment of aircraft carbon fiber-reinforced plastic skin by plastic abrasive jet machining

In this study, a new pretreatment method was proposed for efficient nondestructive substrate pretreatment of carbon fiber-reinforced plastic (CFRP) skin stealth coatings for 4th and 5th generation fighter jets, which can effectively replace hand sanding and meet the requirements of high efficiency and damage prevention of the substrate. Erosion experiments were carried out on a commercial sandblasting cabinet by the Taguchi method for CFRP skin pretreatment. The mechanisms of hand sanding and plastic abrasive jet machining (PAJM) were introduced in detail. The advantages of PAJM over hand sanding for CFRP skin pretreatment were investigated in terms of surface morphology, wettability, and adhesion, in order to achieve the objective of enhancing coating adhesion and prolonging the service life of the substrate. These results show that the damage of PAJM-eroded surfaces is lower than that of hand-sanded surfaces, and safe process parameters for no fiber damage are provided. The critical pressure of carbon fiber damage was likely to be 0.4 MPa or lower, and the adhesion of primer could reach 3.6 MPa. This study provides significant guidance for the pretreatment of new-generation aircraft CFRP skin. Highlights The erosion mechanism of plastic abrasive is semi-ductile erosion. Compared with manual sanding, PAJM is more suitable for carbon fiber-reinforced plastic (CFRP) substrates pretreatment. The proper PAJM process can realize the non-destructive CFRP substrate. Obtained the best pretreatment process

Dynamic recrystallization of Sn coatings on carbon-fiber-reinforced plastics during cold spray additive manufacturing

The metallization of carbon-fiber-reinforced plastic (CFRP) is a promising solution for increasing the electrical conductivity of CFRP components used in airplane applications to protect them from lightning strikes. Therefore, in this study, cold spraying was used to deposit Sn coating on an epoxy-based CFRP substrate with three different pass numbers (24, 48, and 96) at a gas temperature of 473 K, and the microstructural evolution of the deposited Sn coatings was examined. The grain size of the cold-sprayed Sn coatings gradually decreased as the pass number increased, with 96-pass deposition producing relatively homogeneous, finer-grained microstructures with an average grain size of 4.5 µm. Additionally, increasing the pass number enhanced the in-grain local misorientation of the Sn coatings, which can be correlated with the geometrically necessary dislocation density. The grain refinement observed in conjunction with the formation of dislocation substructures indicated that dynamic recrystallization occurred in the Sn coatings during the multipass cold spraying process, enabling synergistic strengthening. The dynamic recrystallization fraction increased with the pass number, eventually exceeding 60% after the 96-pass deposition. Consequently, as the pass number increased, the hardness of the deposited Sn coatings increased, resulting in more homogeneous hardness distributions along the building direction. Additionally, a thermomechanical effect originating from the low melting temperature of Sn was particularly observed. The findings of this study emphasize the critical nature of cold spray additive manufacturing for the metallization of CFRP components and strengthening of deposited metals.

Thermal barrier coating for carbon fiber-reinforced composite materials

Carbon fiber-reinforced plastic (CFRP) composites are widely employed in lightweight and high performance applications including supercars, aero-vehicles, and space components. However, although carbon fibers are thermally stable, the low thermal endurance of the matrix materials remains a critical problem in terms of the performance of the material. In this study, we proposed a new, Al 2 O 3 -based thermal barrier coating (TBC) for the CFRP composites. The TBC comprised α-phase Al 2 O 3 particles with a mean diameter of 9.27 μm. The strong adhesion between the TBC and the CFRP substrate was evaluated using a three-point bending test. When the CFRP substrate was subjected to a 500–700 °C flame, the 1.45-mm thick TBC protected the CFRP substrate remarkably by reducing the surface temperature to 188–228 °C. The thermo-mechanical responses of this TBC/CFRP composite were analyzed after thermal shock tests. Surprisingly, 50% of the pristine flexural strength of the TBC/CFRP composite was preserved, whereas that of neat CFRP was reduced significantly by 95%.

Effect of barrier layer on moisture absorption of thin carbon-fiber-reinforced plastic mirror substrates

Carbon-fiber-reinforced plastic (CFRP) has a higher strength-to-weight ratio and forming flexibility than metals, making it suitable for fabricating lightweight x-ray mirrors. However, CFRP has the disadvantages of print-through and deformation due to moisture absorption, which have prevented its use in optical mirrors. To expand the application of CFRP, we studied the formation of a moisture barrier layer on CFRP substrates. We formed a flattening layer a few micrometers thick on a CFRP substrate, following which we coated the substrate with SiOx as a moisture barrier. The effect of moisture absorption was then evaluated using accelerated aging tests. We found that the diffusivity of the CFRP substrate at 60°C and a relative humidity of 100% was ∼2 × 10 − 6 mm2 h − 1, which is 1/500th that of the barrier-less substrate. In the tests, the moisture absorption rate increased after ∼800 h. As we observed cracks on the flattening layer after 600 h, the rate increase could be associated with these cracks. Considering the damage to the barrier layer, we propose a modified model for the time profile, which is congruent with the observed time profile of the moisture content.

Implementation of fiberglass in carbon fiber composites as an isolation layer that enhances lightning strike protection

In order to investigate the influence of anticorrosion-used fiberglass isolation layer on the lightning strike protection (LSP) of carbon fiber reinforced plastic (CFRP), the specimens, prepared by inserting a fiberglass layer between the expanded metal (Al or Cu) foil and CFRP substrate, were subjected to the artificial lightning of standardized Waveform C (200 Coulombs) and Waveform D (100 kA). The post-lightning damage was evaluated via visual inspection, ultrasonic scanning and residual strength test. The experiments found that the fiberglass isolation layer enhanced the LSP effectiveness of CFRP. While the majority of LSP solutions are based on the current “discharge” mechanism of highly conductive materials, the fiberglass isolation layer probably belongs to the “isolating” mechanism. The inherent electrically insulating, thermally insulating and refractory properties of fiberglass make it possible to construct an isolation layer that suppresses the downward penetration of lightning electric and heat into the underlying CFRP, preventing the CFRP from being ablated by internal Joule heat and external heat.

Ultra-thin carbon fiber mirrors: nickel plated, optical fabrication and thermal deformation test

The aperture of space remote sensing camera is increasing, and the demand for lighter weight is getting higher and higher. With the advancement of active optics, the thickness of optical components has gradually grown to light and thin. It is extremely difficult to develop ultrathin mirrors using brittle materials such as traditional optical glass and silicon carbide. Due to advantages such as low density, high specific stiffness, low thermal expansion coefficient, toughness, and additive rapid manufacturing properties, carbon fiber reinforced plastic (CFRP) is one of potential applications for large-diameter ultra-thin mirrors. However, the carbon fiber composite material is a two-phase material that cannot be used as optical surface and must be surface-modified. In this paper, the surface modification of CFRP substrate was carried out by chemical nickel plating and nickel electroplating. The modified nickel layer covers all surfaces of CFRP substrate, and nickel layers satisfying the thickness, bonding force, and internal stress requirements. A Φ100 mm aperture ultra-thin carbon fiber mirror developed, after optical fabricating, its surface accuracy RMS is better than λ/15. Thermal deformation analysis and test show that the thermal deformation of ultra-thin carbon fiber mirrors is mainly manifested by the change of radius of curvature, which is caused by the thickness error of the nickel layer on the front and rear faces. In addition, although thermal deformation caused by the lamination angle error of CFRP substrate is relatively small in value, it should still be given enough attention, because the astigmatic error produced is hard to eliminate.

CFRP grinding wheels for high speed and ultra-high speed grinding: A review of current technologies and research strategies

This paper primarily reviews the general condition of research on and applications of high speed and ultra-high speed grinding technology. Both technical requirements for grinding wheels used for high speed and ultra-high speed grinding, and existing problems with the current processes are pointed out. Specific to these problems, the discussion regarding high-performance lightweight grinding wheels with a carbon fiber reinforced plastic (CFRP) substrate focuses on three aspects, i.e., design and manufacture, experimental grinding research, and practical industrial applications. Based on the summary of existing research and the application status of the CFRP grinding wheel, existing deficiencies are qualitatively discussed. Focusing on the development of a lightweight CFRP grinding wheel for high speed and ultra-high speed grinding at the end of the paper, some key technical problems with CFRP substrate grinding wheels, such as controlled performance, controlled shape, and the grinding mechanism, are identified, along with further research strategies to resolve them.

Studies of the moisture absorption of thin carbon fiber reinforced plastic substrates for x-ray mirrors

We study a lightweight x-ray mirror with a carbon fiber reinforced plastic (CFRP) substrate for next-generation x-ray satellites. For tightly nested x-ray mirrors, such as those on the Suzaku and ASTRO-H telescopes, CFRP is the suitable substrate material because it has a higher strength-to-weight ratio and forming flexibility than those of metals. In flat CFRP substrate fabrication, the surface waviness has a root mean square (RMS) of ∼1 μm in the best products. The RMS approximately reaches a value consistent with the RMS of the mold used for the forming. We study the effect of moisture absorption using accelerated aging tests in three environments. The diffusivity of the CFRP substrate at 60°C and at relative humidity of 100% is ∼9.7×10−4 mm2·h−1, and the acceleration rate to the laboratory environment was 180 times higher. We also develop co-curing functional sheets with low water-vapor transmissivity on the CFRP substrate. Co-curing the sheets successfully reduced the moisture absorption rate by 440 times compared to the un-co-cured substrate. Details of the CFRP substrate fabrication and moisture absorption tests are also reported.

Experimental studies on performance of reinforced concrete beam strengthened with CFRP under cyclic loading using FBG array

Investigations are increasingly being carried out in the area of utilizing Fiber Reinforced Plastic (FRP) materials for retrofitting and repairing existing damaged concrete structures due to their excellent properties. Favorable mechanical and material characteristics of FRP composites make them attractive for strengthening applications, whereas relatively higher material costs, insufficient knowledge in mechanics of their behavior, long-term durability and lack of related design codes are the issues that need to be addressed for mainstream application of these materials. Although there has been growing interest and field applications of strengthening concrete structures using Carbon Fiber Reinforced Plastic (CFRP) sheet/plate, very little information exists regarding the flexural fatigue behavior of reinforced concrete beams strengthened with CFRP. A common cause of failure in such strengthened members is associated with the debonding of CFRP substrate from the concrete in an abrupt manner. In order to understand the mechanism of debonding in strengthened concrete structures, embedment of strain sensors (Fiber Bragg Grating (FBG) array) between the concrete and CFRP is proposed in this paper. Due to the compatibility with CFRP material and being small in size, fiber optic sensor is a good choice for embedding at the interface to measure interfacial strain. This paper presents the experimental studies carried out on CFRP strengthened concrete members subjected to cyclic loading. A special emphasis has been placed on understanding the failure pattern using the embedded FBG sensors. Based on the studies it is concluded that the strain at the interface of CFRP strengthened concrete members can be measured.

Fabrication of Aluminum Coating onto CFRP Substrate by Cold Spray

Carbon fiber-reinforced plastic (CFRP) has a great potential application in aircraft fuselage due to its light weight, high specific stiffness and high specific strength. It is crucial to coat the CFRP surface with an electrically conductive material to avoid the damage from lightning strike. Cold spray process has been developed for metallic coating technique. In this study, aluminum coating was fabricated onto the CFRP substrate using interlayer was investigated. It was difficult to fabricate cold-sprayed aluminum coating directly on the CFRP substrate. Though smaller size aluminum particles could be deposited on the CFRP substrate, but the coating was peeled off when the thickness was around 30 μm. On the other hand, it was possible to deposit aluminum coating on the CFRP substrate by plasma spray process. Our proposed structure is using a thin plasma-sprayed aluminum interlayer on the CFRP substrate before doing the cold spray. The interlayer with larger contact area could retain on the substrate and able to facilitate the deformation of the next incoming cold-sprayed particles to build a thick coating. The volume resistivity of cold spray coating is lower than the plasma sprayed aluminum coating because of high process gas temperature in the latter case enhances the oxidation of sprayed particle. Therefore, lower process gas temperature should be used to fabricate lower volume resistivity coating on cold spray.

Structure, electrochemical and wear-corrosion properties of electroless nickel–phosphorus deposition on CFRP composites

This work evaluates the microstructure, and mechanical, elcetrochemical and wear-corrosion properties of electroless nickel–phosphorus (ENP) coatings on carbon-fiber-reinforced plastic (CFRP) composites commonly used in aeronautical and astronautical applications due to their superior properties such as high specific strength and modulus. Experimental results demonstrate that a uniform ENP coating was successfully deposited on a CFRP substrate via electroless plating after appropriate sensitization, activation and mechanical polishing pre-treatments of the CFRP substrate exhibited excellent protection from corrosion and wear corrosion for CFRP composites. The microstructure, phosphorus content, thickness and electrochemical and wear-corrosion properties of the ENP coatings were strongly correlated with the pre-polishing condition (the corresponding surface roughness) of the CFRP substrate. High P content (P > 7 wt.%), low micro-porosity, smooth morphology, high thickness and hardness of ENP coatings on the CFRP substrate were obtained when substrate surface roughness was ≥0.3 μm (grinding with 800-grade emery paper). The resulting electrochemical behavior exhibited a strong passivity that is favorable to enhanced wear-corrosion resistance properties.