بررسي استحكام پسماند خمشي پس از ضربه در صفحه هاي كامپوزيتي مشبك ريخته گري شده

چكيده انگليسي :

83 Investigating Residual Bending Strength Of Molded Grating Composite Panel after Impact Sayed Mohammad Reza Hoseini Andani mohammad hoseini1@me iut ac ir Department of mechanical engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language FarsiSupervisor Dr Mohammad Reza Forouzan forouzan@cc iut ac irAbstractMolded gratings are extensively used in different industries such as aerospace construction and shipbuildingdue to their good mechanical properties such as biaxial strength and stiffness and their significant corrosionresistance and high strength to weight ratio These composites are sensitive to the damage caused by theimpacts Low velocity impacts cause internal damages in the structure and the extent of this damage duringnext loadings decreases the strength of the structure considerably In this study the strength of moldedgrating composites against impact loads and their bending residual strength are investigated For this purpose molded grating composites were modeled as a unidirectional material except in the intersections where itsbehavior was modeled as a bidirectional material Different failure criteria of Maximum stress Maximumstrain Hashin and modified Hashin with suitable degradation model have been employed with modificationsin the VUMAT subroutine that were implemented in the ABAQUS commercial software Materialdegradation model for this material was selected for the purpose that numerical analysis matches with theexperimental results therefore if the damage occurs in any mode the corresponding reduction in the elasticproperties is equal to 5 of the intact material The low velocity impact tests were performed on the gratingcomposite panels by using the drop weight tower with two different drop weights of 5 5 kg falling from 1 mheight and the drop weight of 10 3 kg falling from 1 07 m and 1 5 m heights The results showed that thenumerical analysis predicts the ultimate force and the slope of load displacement diagram with a reasonableaccuracy and correlate well with the experimental results The simulation of three point bending test on theintact specimens showed that Maximum stress and strain failure criteria were higher bounds of the insertedforce however Hashin and Modified Hshin failure criteria were its lower bound Among investigatedcriteria only Hashin criterion was able to predict damaged areas and bending residual strength accurately For the case of 5 5 kg drop weight falling from 1 m height due to the less damage and occurrence of the localdamage under the punch area the ultimate force predicted by the numerical analysis was 19 6 less than theexperimental results For the case of 10 3 kg drop weight falling from 1 07 m and 1 5 m heights load displacement curves obtained from both numerical and experimental analysis were in a good agreement andthe ultimate force predicted by numerical simulation was about 10 more than experimental results KeywordsMolded grating composite Low velocity impact Damage Residual bending strength

حسيني انداني، محمدرضا

بررسي استحكام پسماند خمشي پس از ضربه در صفحه هاي كامپوزيتي مشبك ريخته گري شده

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