توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Effects of variable properties of composites constituents with temperature on superplastic forming process of MMCs
نویسنده(ها): ،
اطلاعات انتشار: هجدهمین کنفرانس سالانه مهندسی مکانیک، سال
تعداد صفحات: ۵
In aerospace applications structures weight is considered as a major performance parameter. One of the most effective ways for weight reduction is superplastic forming. By this technique, not only the weight, but also the stress concentration, the cost, and the manufacturing time are noticeably reduced. Additionally, the components with complicated shapes could be formed in a single manufacturing step. Due to the wide demand for whiskers reinforced metal matrix composites (MMCs) in aerospace industries, many research works have been designed to extend the borders of superplastic forming to MMCs materials. In the present study, an axisymmetric micromechanical finite element model is developed to predict the superplastic behavior of Al–SiC composite. Here, the effects of variations of materials properties on the superplastic forming process are highlighted. In most of the available numerical studies this phenomenon has been ignored. Here, the Internal Stress Superplasticity (ISS) mechanism is considered. This mechanism involves a thermal cycling load (e.g. 100°– 450°–100°c, 50s heating, 150s cooling) accompanied by a constant biasing mechanical load (e.g. 2, 4, 7, 10 Mpa). The effects of variation of yield strength, Coefficient of Thermal Expansion (CTE) withtemperature on plastic strain of the MMC are investigated. According to the results, in the mentioned temperature range, the properties of the MMC matrix material are highly changed. This potentially could affect both the plastic strain amount and rate. As it is seen, the effects of change in yield strength on plastic strain response of the composite are more pronounced than the CTE. In fact, it seems in ISS process, the variation of yield strength plays a key role.<\div>

۲Utilizing Genetic Algorithm for Multiobjective Structural Optimization of Helicopter Rotor Blades
نویسنده(ها): ،
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۶
Optimization of helicopter components relies, perhaps to a greater extent than for any other aerospace vehicle, on the tight integration of a variety of aeronautical engineering disciplines. Utilizing a method for multi–objective design optimization of structure of rotor blades has been a challenging endeavor.In this paper the focus is on two major subjects. Firstly, Genetic Algorithm (GA) is introduced as an effective tool for the purpose of multi–objective optimization of the blades specially the composite ones. In the process of optimization the weight of the blade, the deflections due to aerodynamic and inertia loads at hovering and also the stress tolerance of structure (Safety Factor) are considered as design parameters and the laminate configuration (i.e. the fiber orientation, thickness and number of layers) and the material as design variables. Secondly, a comparison of the effectiveness of the optimization process for composite and isotropic blades and also the optimum blades achieved from each process is presented. The results show that the GA can be utilized as an effective optimization tool especially for the structure of composite blades which has more complicated searching space. Better structural characteristics of composite blades compared to isotropic ones shows that they have the potential to replace the ordinary blades<\div>

۳The Effect of Post–Cure Process on The Thermo–Mechanical Behavior ofHybrid Carbon\Glass\Epoxy Laminated Composites
نویسنده(ها): ، ،
اطلاعات انتشار: کنفرانس دو سالانه بین المللی مکانیک جامدات تجربی، سال
تعداد صفحات: ۵
This paper examined the influence of post–cure process on the mechanical and physical properties of a hybrid carbon\glass\epoxy laminated composite. Post–cure process is currently a very popular restorative technique for the purposes of increasing material cure, and thus enhancing properties of composite materials. To this end, hand fabricated composites cured in room temperature and then subjected to immediate post–cure process (100oC for 4 hours). The specimen then was allowed to cool to the room temperature naturally. Finally, tensile tests and thermo–mechanical analysis were carried out to measuring the thermo–mechanical properties of specimens. Compared with the prior composites,the results showed that post–curing process increase the young’s modulus and strength of composites. It is also found that post–curing process slightly increase glass transition temperature and has a negligible effects on coefficients of thermal expansion of composites. Therefore, the post–cure temperature and duration is an effective way of increasing in mechanical properties and reducing the destructive effectsof residual stresses in laminated composites.<\div>
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