Comparison of fatigue resistance characteristics of aluminum alloys and carbon laminates

It is known that many researchers of the mechanical properties of layered composites claim that in comparison with traditional structural metals and alloys, composites have serious advantages, mainly associated with high specific characteristics of static and fatigue strength. It should be noted that a well-founded idea of the advantages of composites strength characteristics is of particular importance for the elements of aircraft structures, taking into consideration an extremely important issue of operation safety. Unfortunately, at least, such a reasonable conception with respect to fatigue resistance characteristics has not been formed yet, consequently, a number of points concerning application of laminated composites in aircraft structures remain unanswered. The article presents a method and an example of comparing the fatigue life of the specimens with the open hole made of modern aluminum aviation alloy 1163T7 and carbon laminate AS4-PW. An obvious advantage of fatigue life of carbon composite materials compared to aluminum alloy at room temperature is noted. On the basis of a number of significant factors to be considered, the specified advantage can be largely diminished. First of all, these factors include the following: effect of temperature and humidity and degradation of the resistance characteristics of layered composites after impact damage. Taking into account the effect of the listed factors, the results of the comparison for the fatigue resistance characteristics of the specimens under consideration are presented. It is noted that the mentioned comparison was carried out using experimental data for the specimens considered under cyclic loading with constant amplitudes as well as under irregular loading, therefore, the comparison results may be slightly different. Nevertheless, it is obvious that the similar comparison presents relevant interest and should be considered when drawing final conclusions about the advantages (or their absence) of the fatigue resistance characteristics of carbon laminates over aluminum alloys.