Fibers dynamic friction

Fig. 6.15 Flow chart outlining how the dynamic frictional shear stress, rd, in fiber-reinforced ceramics can be calculated from cyclic loading experiments.

Static friction decreases with an increase in load, and the static coefficient of friction is lower than the dynamic coefficient. The tendency to creep must be considered carefliUy in FEP products designed for service under continuous stresses. Creep can be minimized by suitable fillers. Fillets are also used to improve wear resistance and stiffness. Compositions such as 30% bronze-fiUed FEP, 20% graphite-filled FEP, and 10% glass-fiber-filled FEP offer high PV values ( 400(kPa-m)/s) and are suitable for beatings. 

ETFE resins are very often compounded with varied ingredients, such as glass fibers and bronze powder, to attain certain mechanical properties. For example, glass fibers are added at 25 to 35 wt% levels to increase modulus and improve wear and friction characteristics. By adding 25% glass fibers, for example, the dynamic coefficient of friction is reduced from about 0.5 to about 0.3 69... 

Polymer emulsions (150 to 250 nm) deposit on the external surface of fabrics and on fibers. They improve the softness and the ease of ironing since they reduce both static and dynamic coefficients of friction. 

Material Fiber orientation degrees Static Young s GN/m 1 modulus, Dynamic Young s GN/m modulus, Internal friction, 10-" First- harmonic frequency, kHz... 

Figure 11.36 Dynamic coefficient of friction versus temperature of DuPont Engineering Polymers Vespel CR-6100—30% carbon fiber-reinforced PFA [18], PV = 0.68 MPa x 30 m/s no lubrication.

Figure 12.9 Dynamic coefficient of friction versus temperature of Victrex pic Victrex 450FC30—lubricated, 30% carbon fiber/PTFE PEEK [5].

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