چكيده به لاتين
Structures made of multilayer composite materials have gained special importance in recent decades. Innovations in this industry have resulted in significant weight reductions in composite structures. Composite materials offer many properties compared to metal alloys, especially in cases where the high ratio of strength and stiffness to the weight of the structure is required. The use of aluminum sheets in aircraft fuselages has been common in the past due to its low weight and good impact resistance, and over time, aluminum has given way to composite materials. Each of the two aluminum materials and composite layers have disadvantages that can be problematic to use alone in aerospace industry. By inventing fiber-metal laminates, which are formed by placing metal layers between composite layers, researchers have achieved a structured composite material that, while having the properties of aluminum and metal layers, also eliminates the disadvantages of each. When using fiber-metal laminates in different structures, there is a need to make holes and openings in the composite material for different purposes. Analyzing the stress concentration created in different layers of multilayer composites around these openings with numerical and experimental methods can be difficult due to the small openings relative to the whole structure or the complexity of the material structure, so using an analytical method to analyze the stress concentration around openings alongside Other methods are useful. The classical theory of multilayers is used for stress analysis in composite layers. Due to the discontinuity in the existing problem, this method needs to be expanded. For this purpose, the analytical method presented by Lekhnitsky, which is based on the use of potential functions in complex space as well as mapping, is used. The advantage of this method compared to other analytical methods as well as finite elements is the ability of coding and parametric solution of the problem. In this thesis, the stress and strength of metal and composite layers in perforated fiber-metal laminates are discussed using the presented analytical method. By changing the geometric parameters of the opening shape and also applying uniaxial, biaxial and shear loads in a variety of standard grades of these laminates, the effect of maximum stress around the opening and the strength of the weakest layer of each of the mentioned parameters is obtained.
