مطالعه تجربي و عددي رفتار الاستيك صفحه ساندويچي با هسته موج‌دار يكپارچه متشكل از پارچه حلقوي پودي سه‌بعدي

چكيده انگليسي :

IUT 9010818Degree Ph D Title Experimental and numerical study of the elastic behavior of the integrated corrugated core sandwichpanels comprised of 3 D weft knitted fabricsAuthor Hamid AbedzadeAtarSupervisor Dr M Zarrebini Dr H HasaniDepartment Textile EngineeringDate Jan 8 2020Language PersianAbstract Corrugated core sandwich panels are comprised of a relatively thick and low density corrugatedcore sheet The core is sandwiched between two usually thin and stiff skins The use of corrugated coresandwich panel is very prevalent in mechanical and aerospace structures Composite forms of these structuressuffer from delamination phenomenon due to the rather weak adhesion between the core and the skins In thisthesis using recent advances in the field of 3 D weft knitting technology the reinforcements of integratedcorrugated core sandwich panel with rectangular hat type or trapezoid and triangular core geometries wereknitted In order to be able to compare composite samples of similar weights the 3 D reinforcement withdifferent core geometries were prepared using glass fiber yarns of different yarn counts during knittingoperation VARTM composite making method was used to fabricate composite samples using epoxy resin This research also examines the effect of 3 D reinforcement and the structural integrity on mechanicalproperties of corrugated core sandwich panels This was achieved using 2 D weft knitted fabrics which werelaminated in such a manner that the non integrated structure with rectangular core was fabricated with upmost similarities to the integrated structure In non integrated structures the resin bonds the core to the skinswhile in the integrated composites in addition to the resin yarns also participate in bonding of theconstituent layers to each other Flexural stiffness transverse shear rigidity and core shear modulus of thecomposites samples were determined using 3 point and 4 point bending tests The results of flexural loadingpointed to better performance of the triangular structure in the direction of corrugation The triangularstructure was found to have higher transverse shear rigidity and core shear modulus in the direction ofcorrugation than the hat type or rectangular structures It was also found that the hat type structure has highertransverse shear rigidity and core shear modulus in the transverse direction of corrugation than the otherstructures It was found that beams made of the integrated structure with rectangular core perform better inthe transverse direction of corrugation This phenomenon is important due to the fact that corrugated coresandwich panel are mostly used in the transverse direction of corrugation The results showed that theintegrated structure has greater flexural stiffness in the transverse direction of corrugation than the non integrated structure However the integrated structure was found to have low performance in the direction ofcorrugation than the non integrated structure Experimental modal analysis revealed that the effect of coregeometry and structural integrity of corrugated core sandwich panel composites on the natural frequency issignificant It was found that changes in the core wall geometry from 41 to 90 reduces the naturalfrequency Additionally it was found that the natural frequency of the integrated structures is significantlyhigher than that of the non integrated structures This phenomenon emphasizes that the natural frequency canbe changed without the need to alter mass or dimensions of the structure using 3 D weft knitting technology The finite element results of the elastic constants and natural frequency of structures both in the direction ofcorrugation and in the transverse direction of corrugation were found to be highly compatible with theexperimental results Key words Corrugated core sandwich panel 3 D weft knitted fabric Integrated structure Flexural stiffness Transverse shear rigidity Core shear modulus Natural frequency

عابدزاده عطار، حميد

مطالعه تجربي و عددي رفتار الاستيك صفحه ساندويچي با هسته موج‌دار يكپارچه متشكل از پارچه حلقوي پودي سه‌بعدي

ساختار ساندويچي با هسته موج‌دار , پارچه سه‌بعدي حلقوي پودي , ساختار يكپارچه , سفتي خمشي , صلبيت برشي عرضي , مدول برشي هسته , بسامد طبيعي