6 research outputs found
On the effective shear modulus of composite honeycomb sandwich panels
U radu je odreÄen efektivni modul klizanja kompozitnog panela sa saÄastom ispunom. Ovaj elastiÄni koeficijent predstavlja veoma važnu karakteristiku kompozitnih panela, naroÄito kod kompozitnih konstrukcija koje su izložene uvijanju kao i kombinovanom uvijanju sa savijanjem. Analizirane strukture u ovom radu sastoje se od gornje i donje kompozitne ploÄe (razliÄitih tipova karbonskih vlakana, T300, AS4 u epoksidnoj matrici) kao i saÄaste ispune (HexWeb EC engineered core). PolazeÄi od klasiÄne teorije lamine, efektivni modul elastiÄnosti klizanja je odreÄen za svaki sloj u kompozitnoj ploÄi. Ovi slojevi su spojeni u jedinstveni kompozitni sloj za razliÄita usmerenja vlakana kao i debljine lamina. ElastiÄni koeficijenti saÄaste ispune HexWeb srediÅ”njeg sloja kompozitnog panela su izraÄunati koristeÄi teoriju Master Evans u cilju dobijanja ekvivalentnih vrednosti. Za proveru predloženog pristupa koriÅ”Äen je metod konaÄnih elemenata, u cilju dobijanja polja pomeranja, deformacija i napona u kompozitnim ploÄama i saÄastoj ispuni. Dva tipa numeriÄkih modela su uporeÄena: poÄetni model, pri Äemu su svi slojevi ploÄe modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama. ZakljuÄeno je da se ekvivalentni metod odreÄivanja modula klizanja kompozitnih panela sa saÄastim ispunama može efikasno primeniti u sluÄajevima kada su gornja i donja kompozitna ploÄa simetriÄnog slaganja ili uopÅ”te kvaziizotropna.In the presented paper the effective shear modulus of composite plates with honeycomb core is determined. This elastic coefficient represents one very important property, especially in constructions subjected to torsion and combined bending - torsion. The structures investigated in this research consisted of top and bottom plates (of different types of carbon fibers, T300, AS4 in epoxy matrix) and honeycomb core (HexWeb engineered core). Starting from classical lamination theory, the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped' into a single composite layer for different fiber orientations and plies thicknesses. Elastic coefficients for the HexWeb engineered core were obtained using Master and Evans relations for the equivalent properties of honeycomb cores. To verify this approach, finite element method was used to determine the displacement, stress and strain field on composite plates with honeycomb core. Two types of models were compared: the initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients. It was found that the method of effective shear modulus calculation can successfully be used in situations where top and bottom plates are symmetric or quasi isotropic in general
Calculation of the effective shear modulus of composite sandwich panels
U radu je predstavljena metoda proraÄuna efektivnog modula smicanja kompozitnih panela sa sendviÄ ispunom. Ovaj koeficijent elastiÄnosti predstavlja vrlo važnu karakteristiku materijala, posebno kod konstrukcija koje su izložene Äistoj torziji ili kombinaciji savijanja i torzije. Strukture koje su ispitivane u ovom istraživanju su ravne ploÄe naÄinjene od gornjeg i donjeg kompozitnog lica i ispunom (jezgrom) od Å”estougaonog kompozitnog sendviÄ materijala. PolazeÄi od klasiÄne teorije laminata odreÄen je efektivni modul smicanja gornje i donje ploÄe za svaki sloj u stoku (laminatu). Ovi slojevi platana se svode u jedan kompozitni sloj sa razliÄitim orijentacijama vlakana i debljine. Da bi se verifikovao ovaj prilaz koriÅ”Äen je Metod konaÄnih elemenata da bi se odredila pomeranja, deformacije i naponi u kompozitnim ploÄama i sendviÄ ispuni. Dva tipa numeriÄkih modela su uporeÄivani: poÄetni model, gde su svi spojevi ploÄe modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama.Calculation Method for the effective shear modulus of composite plates with sandwich cores is presented. This elastic coefficient represents one very important material property especially in constructions subjected to pure torsion and combined bending - torsion. The structures investigated in this research are flat plates made of top and bottom composite facesheets and hexagonal composite material sandwich core. Starting from classical Lamination theory the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped into a single composite layer for different fiber orientations and plies thicknesses. To verify this approach Finite element method was used to determine the displacement, stress and strain field on Composite plates with Sandwich Cores. Two types of models were compared: The initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients
Failure of mounting bolt of helicopter main gearbox support strut
The mounting bolt of helicopter main gearbox support strut was fractured into two pieces during the flight mission. The fracture occurred at the root of the first engaged thread of the bolt-nut assembly. Visual inspection of the fracture zone revealed cracks, formed by interlinking of corrosion pits, at the almost all thread roots of the bolt. Energy dispersive spectroscopy disclosed significant damage of the cadmium plating as well as the presence of large amounts of corrosion products at the bolt threads. Through the fractography and metallography analysis, it was found that the mounting bolt failed due to hydrogen-induced intergranular stress corrosion cracking (HI-IGSCC). The finite element (FE) analysis confirmed that the crack origin was located at the area with the maximum tensile stress in the bolt
Failure of mounting bolt of helicopter main gearbox support strut
The mounting bolt of helicopter main gearbox support strut was fractured into two pieces during the flight mission. The fracture occurred at the root of the first engaged thread of the bolt-nut assembly. Visual inspection of the fracture zone revealed cracks, formed by interlinking of corrosion pits, at the almost all thread roots of the bolt. Energy dispersive spectroscopy disclosed significant damage of the cadmium plating as well as the presence of large amounts of corrosion products at the bolt threads. Through the fractography and metallography analysis, it was found that the mounting bolt failed due to hydrogen-induced intergranular stress corrosion cracking (HI-IGSCC). The finite element (FE) analysis confirmed that the crack origin was located at the area with the maximum tensile stress in the bolt
Failure of mounting bolt of helicopter main gearbox support strut
The mounting bolt of helicopter main gearbox support strut was fractured into two pieces during the flight mission. The fracture occurred at the root of the first engaged thread of the bolt-nut assembly. Visual inspection of the fracture zone revealed cracks, formed by interlinking of corrosion pits, at the almost all thread roots of the bolt. Energy dispersive spectroscopy disclosed significant damage of the cadmium plating as well as the presence of large amounts of corrosion products at the bolt threads. Through the fractography and metallography analysis, it was found that the mounting bolt failed due to hydrogen-induced intergranular stress corrosion cracking (HI-IGSCC). The finite element (FE) analysis confirmed that the crack origin was located at the area with the maximum tensile stress in the bolt. (C) 2016 Elsevier Ltd. All rights reserved