Reinforced plastics fatigue behavior

Jones CJ, Dickson RF, Adam T, Reiter H, Harris B. Environmental fatigue behavior of reinforced plastics. Compos 1983 14(3) 288-293. 

The rate dependence of fatigue strength demands careful consideration of the potential for heat buildup in both the fatigue test and in service. Generally, since the buildup is a function of the viscous component of the material, the materials that tend toward viscous behavior will also display a sensitivity to cyclic load frequency. Thus, thermoplastics, particularly the crystalline polymers like polyethylene that are above their glass-transition temperatures, are expected to be more sensitive to the cyclic load rate, and highly cross-linked plastics or glass-reinforced plastics are less sensitive to the frequency of load. 

Reinforced Plastics Congress, British Plastics Federation, London, Paper No. 19, pp 145-151 Russell AJ, Street KN (1985) Moisture and temperature effects on the mixed-mode delamination fracture of unidirectional graphite/epoxy. Delamination and debonding of materials, ASTM 537 STP 876, American Society for Testing and Materials, Philadelphia, pp 349-370 Saito H, Kimpara I (2007) Effect of water absorption on compressive strength after impact and post impact fatigue behavior of woven and knitted CFRP laminates. Key Eng Matra-334-335 517-520... 

Characterizing Fatigue Behavior in Fiber Reinforced Plastics... 

Figu re 1.64 Various criteria for characterizing fatigue behavior in fiber reinforced plastics (schematic) [ /18]... 

The well-known S-N curves are - probably for historical reasons — the method most often used to describe fatigue behavior for fiber reinforced plastics. In this discontinuous (as defined in the previous section) procedure, the fatigue criterion is typically fracture, that is total failure of the test specimen. Statistic evaluation leads to statements regarding the probability of fracture P, Figure 1.65. 

Watanabe M. Effect of water environment on fatigue behavior of fiberglass reinforced plastics. In Tsai SW, editor. Composite materials, testing and design (fifth conference), ASTM STP 674, American Society for Testing and Materials 1979. p. 345-367. 

Reinforced plastics form an important area of structural application of plastics since the modulus and strength of plastics can be increased significantly through reinforcement. In reinforced plastics, the polymer (popularly called the resin) forms the matrix and a filler (mostly used in the form of fibers, hut particles, for example glass spheres, are also used) provides the reinforcing effect. In view of then-distinctive nature and extensive use as materials of construction in load-hearing applications, a special focus has been on analysis of properties of reinforced plastics, especially those reinforced by continuous or discontinuous fibers, as well as their deformation, fi-acture, fatigue, and impact behaviors. 

The influence of time-temperature effects on the tensile strength and tensile-tensile fatigue behavior of short-fiber reinforced polyamides (PA 6 and PA 66) has been reported before [7], and it was found that at room temperature (23°C), the tensile strength of these two thermoplastics are virtually the same. This result has made it possible to simplify our analysis by focusing the compatibility study of tensile properties on one of the two PA plastics mentioned above. The focused tensile property analysis of PA 6 based thermoplastics was presented before [10], The current paper has extended the scope of that study to include other important information from the tensile property testing and analysis. 

Harris B, Reiter H, Adam T, Dickson R F, Fernando G, Fatigue behavior of carbon fiber reinforced plastics . Composites, 1990 21 (1) 232-243. 

---