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Kompozitni materiali imajo zaradi velike nosilnosti glede na svojo težo pomembno vlogo v tehniški praksi. Sestavljeni so iz ojačitvenih vlaken oz. granulata ter manj toge matrice, ki ojačitveno strukturo povezuje. Če vlakna in pripadajočo matrico nanašamo v plasteh, dobimo laminat, v katerem ima lahko načeloma vsaka plast drugačne mehanske lastnosti, ki skupaj določajo lastnost laminirane kompozitne strukture. Na lastnosti vplivajo mehanske lastnosti samih vlaken in matrice v vsaki od plasti, usmerjenost vlaken, debelina posamezne plasti, vrstni red plasti idr. Zaradi usmerjenosti vlaken je posamezna plast običajno ortotropna, celoten laminat pa anizotropen. V delu je predstavljena teorija laminacije s poudarkom na teoretičnem napovedovanju elastičnih lastnosti kompozitnih struktur. Mehanski model je uporabljen za formulacijo končnih elementov na podlagi Kirchoffove teorije tankih plošč. V nadaljevanju so nato obravnavane teoretične osnove numerične optimizacije. Predstavljena je lastno razvita programska koda za optimizacijo porazdelitve debeline slojev laminata, kjer si kot cilj zastavimo izboljšanje togosti strukture. Kot praktični primer uporabe predstavljenih algoritmov je izveden še optimizacijski postopek kompozitne šasije monokoka dirkalnika, uporabljenega na tekmovanju Formula Študent. Due to their high load carrying capacity, the adoption of composite materials throughout the industry is spreading at an ever faster pace. They are constructed primarily out of a binding matrix and fiber reinforcements. By stacking consecutive layers of a fiber-matrix mixture on top of each other, we are left with a laminated structure, each possessing unique mechanical properties. The properties are influenced by the characteristics of the matrix and fibers themselves, their thickness, distribution, orientation, stacking sequence etc. It is generally assumed that a single layer exhibits orthotropic properties, whilst the laminate is considered anisotropic. The scope of the thesis features an examination of the classical lamination theory, focused on the theoretical prediction of elastic properties of composite plies. The theoretical models are then implemented into a finite element formulation based on the Kirchoff -Love theory of elastic plates. After that an optimization study is performed, using an optimization algorithm developed by the author, whereby the objective is to maximize the overall stiffness of the structure. As a practical case study a full composite optimization procedure is conducted on a composite chassis, used in the formula student competition. |
