شبيه سازي فرآيند تزريق رزين و طراحي بهينه قالب VARTM ، براي ساخت پوشش كامپوزيتي محافظ سونار شناور دريايي

چكيده انگليسي :

127 Simulation of Resin Injection Molding Process and Optimal Design of VARTM Mold for Fabrication of Marine Vehicle Composite Sonar Dome Hadi Iraji h iraji@me iut ac ir Date of Submission 01 20 2014 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohsen Safavi mosafavi@cc iut ac irAbstractComposite construction is now the material of choice for sonar domes on surface ships and submarines Thedomes provide a smooth flow around sonar transducers and protect them from impact damage Protectivedome of underwater sonar devices should comply with specific requirements with respect to acousticbehavior and protection That s why conventional steel crusts are being replaced by composites in the sonarindustry in many developed countries as well as in Iran Investigation of material properties indicated thatgood sonar transmission at various frequencies was achievable with composite material When this attributeis coupled with weight saving freedom from maintenance and corrosion and ease of fabrication ofcomplex shapes In this research the flow of resin and the parameters which affect it during vacuum assisted resin injectionmolding are analyzed This is the process selected for the production of the composite protective structure This process is commonly used in the production of large sized high quality composite items in smallnumbers It involves a stiff mould half and a flexible membrane that seals the cavity Vacuum is used toconsolidate the preform and atmospheric pressure drives low viscosity resin into the mould cavity The partis cured at room temperature A high permeability medium is added to the preform in order to reduceinfusion time This material modifies flow dynamics during preform infusion Proper filling of the mold and soaking of the fibers are critical in vacuum assisted resin injection molding Inadequate soaking can result in faulty items and higher costs Because of their common inability toproperly model the process manufacturers mostly prefer to use traditional manual methods These methods however involve the use of larger amounts of resin which in turn results in higher evaporation andpollution and lower quality and durability of the final product Simulation of the flow of resin can be a goodway for ascertaining the proper filling of molds before the resin is congealed Hence we studied the processand the equations and parameters involved in the modeling of the flow of resin To conduct this study wemeasured permeability and porosity of three types of glass fiber tissue and the way these parameterschanged with pressure The results were fed to a computer program for analysis During the VARTMprocess the flow front velocity changes imply that impregnated preform thickness the porosity and thepermeability values of the wet area varies with pressure gradient The preform porosity decreased as thepressure increased and was affected by compaction of the preform locally with the pressure gradient Preform permeability changed due to the compaction and flow pressure It was increased as the compactionpressure increased and decreased as the Flow pressure increased The largest effect of compaction pressureon permeability and in general the preform permeability decreased as the compaction and flow pressurewere increased Simulation was done using Fluent software Ansys and the results were compared toexperimental ones so that their validity could be established Simulated process times show 10 to 20 error which is probably due to error in the measurement of parameters thickness changes during simulationnot being accounted for and general software error The optimal strategy for resin injection was eventuallydetermined through trial and error Key wordsModeling Resin Injection VARTM Composite sonar dome

ايرجي، هادي

شبيه سازي فرآيند تزريق رزين و طراحي بهينه قالب VARTM ، براي ساخت پوشش كامپوزيتي محافظ سونار شناور دريايي

مدل سازي