Carbon fibers (CFs) have high specific tensile strength, high modulus, and outstanding wear resistance, and are widely used for the reinforcement of advanced composite materials. CF-reinforced thermoplastic composites have received much attention because of their easy processability and recycling convenience compared with thermosetting composites. Surface treatment of CFs is generally employed to increase the surface functional groups and interfacial adhesion between the CFs and the surrounding polymer matrix. In this review, we explore recent advances in the surface treatment of CFs and preparation of CF/thermoplastic composites. The thermal, mechanical, and electrical properties of the composites are also discussed.

Recent advances in carbon-fiber-reinforced thermoplastic composites: A review

In most areas where weight reduction is crucial, carbon fiber reinforced composites (CFRPs) are an excellent choice. Carbon fiber, besides its structural role, can be applied for several secondary functions as well, based on its electrical properties; for example, it can be used for crosslinking, welding, as a sensor and it can also facilitate self-healing. By merging these functions, a multifunctional part or structure can be created. In this article, we review multifunctional application examples of reinforcing carbon fiber. The focus is on utilization: which additional function and what physical layout can be used with CFRP. In a summarizing table (Table 1), we classified the presented examples according to their secondary function, the material used and the physical layout. With the combination of different functions, important materials can be created for the energy and transportation industry, for autonomous vehicles and for Industry 4.0.

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Multifunctional application of carbon fiber reinforced polymer composites: Electrical properties of the reinforcing carbon fibers – A short review

Lightning strike protection (LSP) and electromagnetic interference (EMI) shielding topics have been extensively investigated, since composite material was first introduced to an aircraft a few decades ago. Generally, electrically and thermally conductive materials, such as metallic foils, metal mesh, ply-integrated interwoven wires, a continuous conductive path of low-resistance materials, and highly conductive nanoparticles and nanoflakes are used to dissipate the high-density current, shockwaves, electromagnetic forces/charges, and heat generated during lightning strikes. This study deals with the fabrication of pre-impregnated (prepreg) composite structures of carbon and glass fibers incorporated with submicron and nanoscale gold (Ag), silver (Au), aluminum (Al), and copper (Cu) films on top of composite surfaces during the curing process, and determining the effectiveness of LSP and EMI shielding. Initially, electrical conductivity experiments were conducted on composite test coupons and the electrical properties investigated under tensile loadings within the elastic regions of the composites. Test results indicated that the surface resistivity did not change much under the tensile loads. EMI shielding tests confirmed that noise was not audible on an AM radio because of the metallic submicron and nanoscale film surfaces on the composites. During lightning strike tests, a high current of 200-k amps was applied on the surface of the composite structures. The LSP test indicated that after the lightning strike, the resulting damage on both sides of the fiber composite was considerably low due to the metallic films co-cured on the fiber-reinforced composites. An increase in current with the metallic films certainly helped to reduce damage to the composites and avionics systems after lightning strike tests.

https://link.springer.com/content/pdf/10.1007/s42114-020-00135-7.pdf

Investigating the effects of metallic submicron and nanofilms on fiber-reinforced composites for lightning strike protection and EMI shielding

Lightning strike damage behavior of carbon fiber reinforced epoxy, bismaleimide, and polyetheretherketone composites

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 and they are classified and discussed with the help of available literature based on experimental results. Possibilities and limitations to these new findings are also discussed.

Y.Y. Ji

Papers

Ablation damage assessment of aircraft carbon fiber/epoxy composite and its protection structures suffered from lightning strike