Nylon fatigue performance

Cord materials such as nylon, polyester, and steel wire conventionally used in tires are twisted and therefore exhibit a nonlinear stress—strain relationship. The cord is twisted to provide reduced bending stiffness and achieve high fatigue performance for cord—mbber composite stmcture. The detrimental effect of cord twist is reduced tensile strength. Analytical studies on the deformation of twisted cords and steel wire cables are available (22,56—59). The tensile modulus E of the twisted cord having diameter D and pitchp is expressed as follows (60) ... 

Valve components depend on fatigue performance. PAEK compounds can outperform nylons due to superior mechanical properties at temperature, lower moisture absorption and better chemical resistance. PEEK compressor valve plates combine toughness with high thermal and dimensional stability. When PAEK components do fail they tend to do less downstream damage than their metal equivalents. 

Fatigue crack propagation tests were performed on 73-nmi x 73-mm (2.9 in. x 2.9 in.) compact-tension specimens that had been machined from the plaques and then precracked. An electrohydrau-lic closed-loop test machine was used to produce a constant-amplitude, 10-Hz sinusoidal load. Host of the tests were performed in duplicate at room temperature in laboratory air at an average ambient RH of A0%. In view of the slow rate of moisture equilibration in air at room temperature (15), the difference between the ambient RH and that of the nylon being tested was presumed to be unimportant within the time period of the test (3-5 hr). 

A tire is a textile-steel-rubber composite the steel and textile cords reinforce the rubber and are the primary load-carrying structures within the tire. Because of the performance demands of fatigue resistance, tensile strength, durability, and resilience, seven principal materials have been found suitable for tire application cotton, rayon, nylon, polyester, steel, fiberglass, and aramid the latter three materials find primary usage in the tire crown or belt region. 

Nylon, beside its important utility as premium fiber in the textile industry, also serves as an engineering polymer due to its unique properties of rigidity and toughness, low friction coefficient (including self lubrication), high resistance to abrasion and fatigue, supreme chemical resistance (including fire retardancy), as well as excellent thermal and electrical performance. 

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