6972

6514

كارشناسي ارشد

ساخت و توليد

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1390

يازده، 95ص.: مصور، جدول، نمودار

ص.ع. به فارسي و انگليسي

محمدرضا فروزان

حميدرضا ميردامادي

4/6/91

مهران مرادي، مهدي سلماني تهراني

1396/09/18

كتابنامه

مكانيك

مهندسي مكانيك

ID6514

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

Investigating The Flexural Strength of Laminated Glass Polyester Composite Beams Under Impact Loads Mehdi Nikforooz m nikforooz@me iut ac ir Date of submission 2012 03 03 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Reza Forouzan Forouzan@cc iut ac irAbstractComposite materials are a group of materials which have high strength and modulus and low density so theirusage in industry instead of traditional materials like steel and aluminum have increased but these materialsare susceptible to damages that are caused by impact Low velocity impact on composite structures likebeams can cause internal damages which can grow in further loading and cause sudden degradation ofmaterial strength Flexural loads after impact is an example of these loads In this thesis impact resistance andresidual flexural strength of laminated glass polyester composite beams with channel sections wereinvestigated For this purpose some of the existing failure criteria for dynamic failure of composite materialswere searched and among these criteria Hou criteria Hashin criteria maximum strain criteria and puckcriteria were programmed and implemented in abaqus software Simulation of impact and bending afterimpact showed that maximum strain criteria for fiber failure and hou criteria for matrix failure have the bestaccuracy for predicting the place and time of damage occurrence and residual flexural strength after lowvelocity impact Low velocity impact tests were also done with different energies by varying the mass andheight of the impactor and for this purpose 25 centimeter and 50 centimeter beams were used After eachimpact test flexural test was done In impact tests a kind of matrix failure were observed in the corner of thebeam and exactly in the attachment of web and flange of the beam that was due to the delamination and strainconcentration in this place and affected the residual strength after impact in high impact energies For solvingthis problem cohesive element was used Using this element for this kind of failure was an innovative methodthat was not used before in the literature review Some of the results that were extracted from the thesis are asfollows Puck criteria for fiber failure showed to have low accuracy for predicting the damage in tension andcompression in low velocity impact Moreover in numerical simulations by fixing the impactor height andvarying impactor mass three regions were observed in residual flexural strength and modulus after lowvelocity impact versus impact energy for 50 centimeter beam The trend of these regions for residual flexuralstrength were all linear linear region was also observed in the same diagram for 25 centimeter beam Furthurmore by fixing the impactor mass and varying the impactor height three regions were observed In thefirst region the matrix damage was low and its effect on residual strength of the beam was negligible In thesecond region by propagating the matrix damage on the impact surface of the beam residual flexural strengthwas affected a lot so that this property lowered to the half of the intact flexural strength without priordamage In the third region a plateau mode was observed that was due to the large amount of matrix damageon the impact surface of the beam that increasing the impact energy did not affect matrix damage severity alot Keywords composite materials channel section beam low velocity impact residual flexural strength

محمدرضا فروزان

حميدرضا ميردامادي

مهران مرادي، مهدي سلماني تهراني