Wear-resistant additives carbon fibers

Aromatic polyamide fiber, commonly known as aramid liber or Kevlar , is one of the latest wear-resistant additives to be used in thermoplastic composites. Unlike the traditional fiber reinforcements of glass and carbon, aramid is the softest and least abrasive fiber. This is a major advantage in wear applications, particularly if the mating surface is sensitive to abrasion. 

To improve the properties of the raw polymer (wear resistance, creep resistance, thermal and electrical conductivity), various fillers, such as glass fibers, powdered metals, and graphite, are combined with all three types of PTFE polymers, mostly by intimate mixing. Filled fine powders are produced mostly by adding fillers into a dispersion and then coagulating the mixture. Aqueous dispersions can also be modified by the addition of certain fillers, pigments, heat resistant dyes, carbon blacks, and powdered metals, especially when processed into films (see Chapter 6). 

Wood is not abrasive to equipment like inorganic fillers/fibers, but certain desired properties can only be obtained with additions of mineral fillers such as talc (for lubricity and strength), calcium carbonate, calcium oxide, alumina, wollastonite (for scratch and wear resistance), or even Portland cement, as a reactive filler supplying strength and fire retardancy. 

SiC whiskers. The particulates or whiskers were uniformly distributed among the carbon fibers and preforms prepared from the treated fibers were directly infiltrated by molten A1 under applied stress. It was found that the longitudinal tensile strengths of hybrid composites were greatly improved, although their fiber volume fractions were quite low compared to those of conventional composites. With this hybridization method, it is also practical to tailor the fiber volume fraction of composites from 60 to 25 vol%, which is not possible in direct infiltration of fiber preforms by pressure easting. The results obtained lead to the conclusion that particulate or whisker additions do not act directly as reinforcements, but as promoters to improve the infiltration performances of fiber preforms and consequently, increase the strength transfer efficiency of carbon fibers. The addition of particulates or whiskers can also improve other properties of the composites, such as hardness and wear resistance. 

The combination of nanoparticles and short carbon fibers exhibited a clear improvement in the wear resistance of both thermosetting and thermoplastic composites. In addition, this concept allowed the use of these materials under more severe wear conditions, such as higher normal pressures and sliding velocities. A topographic smoothening and a possible rolling effect due to the nanoparticles are supposed to be the reasons for this progress in the friction and wear performance. 

Carbon fibers are added to engineering resins to produce high strength, heat distortion temperatures, and modulus as well as creep and fatigue resistance. Often referred to as the perfect additive for wear and friction resins, carbon fibers also greatly increase thermal conductivity and lower COFs and wear rates. In fact, the strengthened compound may have lower friction coefficients than the base resin. 

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