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butare also dependent on theway bywhich they are processed.There are a variety of processing techniques for fabricatingcomposite parts/structure; resin transfer moulding, auto-clave moulding, pultrusion and filament winding. Out ofthese processes, filament winding involves low cost and isthe fastest technique for manufacturing of fiber reinforcedcylindrical components as high-pressure pipes and tanks.3. Winding methodsThere are two different winding methods: (I) wetwinding, in which the fibers are passed through a resinbath and wound onto a rotating mandrel (II) prepregwinding, in which the preimpregnated fiber tows areplaced on the rotating mandrel. Among these windingmethods, wet winding is more common and widely usedfor manufacturing fiber reinforced thermosetting matrixcomposite cylinders. Compared with prepreg winding,wet winding has several advantages: low material cost;short winding time; and the resin formulation whichcan be easily varied to meet specific requirements.3.1. Winding patternsIn filament winding process, the winding tension caneasily be controlled. Winding tension, winding angleand/or resin content in each layer of reinforcement canbe varied until the desired thickness and strength ofthe composite are achieved. The properties of the fin-ished composite can be varied by the type of windingpattern selected. In general, there are three basic fila-ment winding patterns which are as follows.3.1.1. Hoop windingIt is known as the girth or circumferential winding. Inhoop winding, a high-angle helical winding approachesan angle of 90 . Each full rotation of the mandreladvances the band delivery by one full bandwidth asshown in Fig. 2.Fig. 2. Circumferential or hoop winding [2].θFig. 1. Schematic of the wet filament winding process [1]. 3.1.2. Helical windingIn helical winding, the mandrel rotates at a constantspeed while the fiber feed carriage transverses back andforth at a speed regulated to generate the desired helicalangles as shown in Fig. 3.3.1.3. Polar windingIn polar winding, the fiber passes tangentially to thepolar opening at one end of the chamber, reverses direc-tion, and passes tangentially to the opposite side of thepolar opening at the other end. In other words, fibersare wrapped from pole to pole, as the mandrel arm ro-tates about the longitudinal axis as shown in Fig. 4.Itis used to wind almost axial fibers on domed end typeof pressure vessels. On vessels with parallel sides, a sub-sequent circumferential winding would be done.4. The proposed filament winding machineSchematic layout of the hardware configuration forproposed filament-winding machine is shown in Fig. 5.It consists of three main units: the rotary assembly unit,the delivery unit and the control unit.4.1. The rotary assembly unitThe rotary assembly consists of two pillar blockswhichwere held onto horizontal frame work and motor with agearbox.One of the two blocks is fixed and serves as a ref-erence,while the other one ismovable and can be adjustedlinearly for varying themandrel length. Once themandrelis seated properly into two freely rotating cup holders, themovable pillar block is then locked.At the fixed pillar end,the holder is coupled to the motor gearbox by a system ofpulleys and belt. The gear ratio between themotor and thegearbox is selected as 1:60 and the reduction ratio betweenthe pulleys was taken as 1:2, so that the velocity of themandrel is fixed to 13.6 rpm as shown in Fig.
6.4.2. The delivery unitThe delivery unit consists of filament fibers holder,carriage and lead screw with a guide shaft. The leadscrew is driven by a reversible variable speed motor.The filament fiber holder is just a table with two shafts,one used for carrying one or more of the filament fiberrolls while the other one is used as a guide for the fila-ment fiber during the fabrication process. The carriageconsists of a container and a system of polished guidepins. The container was used for carrying the resin mix-ture while the pins were used as a way to guide the fiberto the resin bath and to smear off excess resin from thewetted fibers after the resin bath. Also, the pins were usedto generate tension in the wetted fibers before reachingthe mandrel. A simplemechanism was used to bring backthe smeared resin from the wetted fiber to the containerand reused again in order to reduce the amount of resinused for preparing the product. An optimum tension of10 N has been used through this work. This gave a fairlyconsistent volume fraction of fibers. It was found [3] thatit is important to generate tension in the later stage of theresin path when the fibers are well wetted to avoid fiberdamage. Greater tension on wetted fiber produced exces-sive fiber damage and low tensions produced specimenswith unacceptably small fiber fractions.4.3. The control unitThe control unit consists of relays, limit switches,timer and counter as shown in Fig. 7. The functionof the control unit is to control the winding processin order to get the proper winding sequence, whichis difficult to reach manually, and to safeguard themotor during operation. The control unit also controlsthe amount of end over wind which is required to pre-vent slippage of the roving when the traverse is re-versed and the mandrel indexing to ensure that eachroving slightly overlaps the previous one to producea uniform lay-up of fibers.5. Specimen fabricationThe setup of the specimen on the winding machine isshown in Fig. 6. The fabrication process consists of fiveFig. 3. Helical winding [2].Fig. 4. Polar winding [2]. steps as follows: the first step is to fix the mandrel whichmay be as aluminum or plastic PVC tubes or any differ-ent cylindrical mandrel shape on the machine blocksusing end fixtures. The second step is to prepare the re-sin bath, which is a mixture of epoxy resin and hardener,using a specific ratio and putting it in the container. Thetype of epoxy resin and hardeners used in this investiga-tion were MW 215 TA and MW 215 TB, respectively. They were mixed in a ratio of 4:1, respectively. Thethird step is to pass the fiber tow through the resinbath and then on the mandrel through a series ofpins. These pins make the fiber straight and reducethe amount of resin in the fibers. The fourth step isto control the speed of screw to give the proposedwinding angle. The fifth step comes after the layersof fibers were wound onto the mandrel, the specimenleft to rotate on the mandrel for 3 h at room temper-ature to prevent resin dropping, then after solidifica-tion the specimen pulled off the mandrel and thencut to the required lengths.The relation between winding angle and the speed ofthe screw for mandrel of diameter 12.7 mm is shown inFig. 8.