جستجوی مقالات مرتبط با کلیدواژه « لایه گذاری » در نشریات گروه « فنی و مهندسی »

It has taken plenty of effort to improve motor case, because it has an effective role in the final performance of rockets. The selection of material for a given case depends on the applied loads (bending, shear, axial) and its final application. Today, in fabrication of rocket motor cases, filament-wound polymer composites are regarded as alternative materials to metals due to their lower weight, higher specific strength and better protection of the propellant against external stimuli. In order to compare the performances of metallic and composite motor cases, the performance factor is used. The performance factor is influenced by the chosen polymer matrix (epoxy, polyether ether ketone or polyamide-imide) and the type of fiber (carbon, glass or Kevlar) as well as lamination arrangement of layers. The manufacturing process of composite cases, respectively, involves mandrel integration, applying thermal insulation on the mandrel, helical and hoop winding, curing and finally proof tests. In order to achieve a high-performance composite case, the polymer matrix is analyzed before and after curing by thermal analysis techniques such as DMA and DSC, and the physical and mechanical properties of small-scale motor and real-scale motor are investigated.

During the last decades a new class of materials named fiber/metal laminates (FMLs) was introduced. It is a hybrid composite consisting of alternating thin layers of metal sheets and fiber-reinforced composite material. FMLs have both low weight and good mechanical properties. In this study, the impact behavior of this attractive material is investigated. The effect of fiber angle, stacking sequence and capacity of test apparatus were examined. In addition specimens have been prepared in two sizes according to two standards of ASTM D256-93a for plastics and then ASTM E23- 01 for metals. Test results show that suitable layering, using more aluminum layers and fiber sheets with zero angle in laminates improve the impact strength. The amount of energy absorption in heavy apparatus is higher than the light apparatus.