Fatigue-type

Thermal fatigue is the fatigue type of most concern. Thermal fatigue results from thermal stresses produced by cyclic changes in temperature. 

Particularly in automotive applications, the design engineer selects materials that will endure periodic fluctuations of both tensile and flexural type loads for the service lifetime of the molded part. Under-the-hood automotive conditions include extremes in ambient temperature combined with possible localized vibrations from the engine and rotation of molded parts (cooling fans) under continuous load. Although deformation will occur due to creep, there is concern regarding fatigue type failure after repeated fluctuations of the applied load. 

Fig. 5.103 SEM of aramid containing composites show a combination of axial splitting and fatigue type fracture mechanism. Poor adhesion is observed as are kink bands (arrows) and local axial splitting.

Fig. 1045 Types of comsioa. (a) General, uniform attack corroaioii. (b) Intergranular corrosion, (c) Selective corrosion, e.g. dezindJication of brass, (d) Stress corrosion cracking, (e) Pitting (f) Layer corrosion (exfoliation), (g) Graphitic oorroiton (h) Corrosion fatigue. Types (b) h) are tniCially assodated with the nature of the metal ...

Figure 1.38 The effect of fatigue type on fatigue resistance at 25°C for Mitsubishi Engineering Plastics Corporation lupilon /Novarex PC resin [18].

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