Nonlinear analysis of laminated composite plates and shells with delaminations using finite element method

Abstract

Laminated composites play an important role in the construction of aircrafts, wind turbines, ships, cars and other components in mechanical and civil engineering. For example, the aerospace structures are made of thin-walled cylindrical or spherical composite shell components having an excellent stiness-to-weight and strength-toweight ratios. It is also well-known that Fiber Reinforced Polymer strengthening of the RC beams and slabs give excellent structural results, low time required and moderate cost. Finally, sandwich plates are widely used in civil engineering as roof and wall panels to provide the thermal isolation of the buildings. For these reasons, numerical analysis of laminated composite and sandwich structures attract the increasing attention of researchers in the various engineering disciplines. It is very important that perfect bond between the adjacent layers within the laminate remain intact for the panel to perform on the designed level. However, the mismatch of material properties between the adjacent layers, along with some other factors, may cause a delamination that reduces the stiness of the component and leads to the unexpected structural behavior. To predict the response of damaged structure, a computational model capable to describe the kinematics of the delaminated structures is required. Several limitations of the Equivalent Single Layer (ESL) laminate theories motivated the researchers to derive the rened (layerwise) plate theories for the analysis of composite laminates. Therefore, the scope of this study is based on the reduction of the 3D elasticity problem to a 2D one using the Generalized Laminated Plate Theory (GLPT) of Reddy, capable to describe the delamination kinematics. The GLPT became the basis for the development of enriched layered nite elements, which are applied in the numerical solution of several structural problems. In addition, layered plate nite elements were applied in the numerical investigation of delaminated composite shells using the simple transformations presented in this study. To accurately capture the buckling phenomena of the laminated composites, as well as for investigation of the in uence of large rotations on the transient response of delaminated composite and sandwich plates, the geometric nonlinearity is taken into account upon the von Karman assumptions. Beside the numerical solution, the analytical (Navier) solution for linear transient analysis of intact rectangular simply supported composite plates is provided based on double Fourier series...

Laminatni kompoziti igraju vaznu ulogu u izradi aviona, vetrogeneratora, brodova, automobila i razlicitih elemenata u masinstvu i gradjevinarstvu. Na primer, delovi kosmickih konstrukcija su izradjeni od tankozidnih cilindricnih ili sfericnih ljuski koje imaju odlicne odnose krutost-tezina i cvrstoca-tezina. Takodje je dobro poznato da ojacanje armirano-betonskih greda ili ploca uz pomoc polimera ojacanih vlaknima daje odlicne rezultate u konstrukcijama, uz mali utrosak vremena i umereno visoku cenu. Konacno, sendvic ploce se siroko primenjuju u gradjevinarstvu u vidu krovnih ili fasadnih panela kako bi se obezbedila termicka izolacija zgrada. Iz ovih razloga, numericka analiza laminatnih kompozitnih i sendvic konstrukcija sve vise privlaci paznju istrazivaca u razlicitim inzenjerskim disciplinama. Veoma je vazno da idealna veza susednih slojeva u laminatu ostane neostecena kako bi se panel ponasao na projektovanom nivou. Medjutim, razlika u materijalnim osobinama susednih slojeva, uz uticaj nekih dodatnih faktora, moze da izazove delaminaciju koja smanjuje krutost konstrukcije i dovodi do njenog neocekivanog ponasanja. Da bi se predvideo odgovor ostecene konstrukcije potreban je numericki model koji je u stanju da opise kinematiku ploce ili ljuske sa delaminacijom. Odredjena ogranicenja teorija laminatnih ploca zasnovanih na jednom ekvivalentnom sloju (ESL) motivisala su istrazivace da razvijaju slozenije (slojevite) teorije ploca za analizu laminatnih kompozita. Iz ovog razloga, predmet ovog istrazivanja zasniva se na redukciji trodimenzionalnog problema teorije elasticnosti na dvodimenzionalni problem primenom Redijeve Opste Laminatne Teorije Ploca (GLPT), koja je u mogucnosti da opise kinematiku delaminacije. GLPT predstavlja osnovu za razvijanje slozenih slojevitih konacnih elemenata koji su primenjeni u numerickom resavanju razlicitih problema. Zatim su slojeviti konacni elementi ploce primenjeni u numerickom ispitivanju laminatnih kompozitnih ljuski sa delaminacijama, primenom jednostavnih transformacija koje su prikazane u ovom istrazivanju. Kako bi se precizno ispitao problem izbocavanja laminatnih kompozita, kao i za ispitivanje uticaja velikih rotacija na dinamicki odgovor kompozitnih i sendvic ploca sa delaminacijama, u obzir je uzeta geometrijska nelinearnost bazirana na von Karman-ovim pretpostavkama...