11580

10633

كارشناسي ارشد

تكنولوژي نساجي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده نساجي

1395

[نه]،137ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

مهدي حجازي، محمد شيخ زاده

محمد ذره بيني،رضا جعفري

1395/08/02

مهندسي نساجي

ID10633

فھرست مطالب صفحه عنوان فھرست ھشت چكيده فصل اول كليات پوسته و كامپوزيت پوسته كليات و مباني كامپوزيت بر مقدماتي و تعريف تاري پودي بعدي سه كامپوزيت مطالعات انجام شده بر روي خصوصيات مكانيكي كامپوزيتھاي تقويت يافته با پارچهھاي سه بعدي تاري پودي شكل منحني كامپوزيتھاي روي بر شده انجام مطالعات فصل دوم آزمايشات و تجربيات مقدمه اوليه مواد كامپوزيتي نمونهھاي و شكل منحني قالبھاي ساخت مراحل و فرآيند كامپوزيتي نمونهھاي در رزين و الياف حجمي و وزني درصد تعيين مكانيكي آزمونھاي فصل سوم تجزيه و تحليل نتايج ضربهاي و خمشي خصوصيات روي بر انحنا اثر بررسي آن بھبود حل راه و تاري پودي بعدي سه كامپوزيتھاي ضعف نقاط ضربه و خمشي خصوصيات روي بر اسفنجدار بررسي اثر ضخامت پوستهي باال و ھستهي اي ضربهاي و خمشي خصوصيات روي بر ھسته در اسفنج حضور اثر بررسي ھشت

Abstract Composite panels reinforced with three dimensional woven fabrics have recently attractedresearcher s attention They could find vast applications in various industries such as aerospace automotive and construction industry due to their intrinsic properties like high specific strength andstiffness low weight thermal and acoustic insulation Three dimensional fabrics are woven usingvelvet technique they consist of two woven layers which are connected to each other by means ofconnecting yarns called pile Unlike conventional sandwich composites these new sandwichpanels have superior core skin binding In spite of curved three dimensional woven composites themechanical properties of flat ones were studied comprehensively In the present study the effect ofcurvature on the flexural and low velocity impact properties of three dimensional woven compositeswere investigated Therefore three different radii of curvatures including 150 70 and 35 centimeters along with two different matrices were considered for preparing of curved composite samples andwere compared with flat ones Bending results show that flexural properties such as flexural strength stiffness and toughness initially increase and then reduce as radii of curvature reduces for bothmatrices From bending results it was found that the optimum value of curvature radii is betweena150 and 70 centimeters Low velocity impact results for polyester samples indicated that impactenergy absorption increased at first and then decreased and finally increased as curvature increases In other words curved composite specimen with the curvature radii of 70 centimeters has absorbedthe least impact energy Thus it could be construed from low velocity impact results that theoptimum value of radii of curvature is about 70 centimeters Two major weak points of this structurehave been realized based on the flexural and low velocity impact test observations which are poorperformance of upper skin under compression stresses and poor performance of core under shearstresses Two solutions were offered to improve compression and shear performance of compositesamples which were thickening the upper skin by using woven glass fabrics and by means of handlay up technique and filling the hollow core of the structure with Polyurethane foam respectively Bending results showed that as the upper skin thickness increases from 0 5 mm to 2 and 3 mm forepoxy composite samples most of the flexural properties increase initially and then decrease whilefor polyester composite samples flexural properties increase In addition the presence of foam in thecore results in better flexural properties for both matrices Low velocity impact results indicated thatthe impact energy absorption reduces as the upper skin thickness increases for both matrices whilethe presence of foam in the core has not significantly reduced the impact energy absorption Flexuraland low velocity impact properties could be enhanced significantly by applying both solutions in asingle sample In other words flexural strength of a composite sample having thickened upper skin 3 mm and foam filled core has been increased about a224 and also the impact energy absorptionhas been decreased 29 6 when compared to the sample without foam in the core and thickenedupper skin Keywords Three dimensional fabric composite curved structure flexural and impactproperties

مهدي حجازي، محمد شيخ زاده

محمد ذره بيني،رضا جعفري