Modeling of impact damage in laminate composite structures

U doktorskoj tezi razmatran je problem modeliranja udarnih oštećenja u laminiranim kompozitnim strukturama. Udari u određene strukture uzrokuju oštećenja, čija je karakterizacija ekstremno zahtevna i složena. Postoje analitički, eksperimentalni i numerički pristupi analize mehanizama nastanka i razvoja tih oštećenja. Pri tome neophodno je proceniti otpor na nastanak i toleranciju već prisutnog udarnog oštećenja. Svi razvijeni modeli udarnih oštećenja, sa određenom tačnošću, aproksimiraju nastalo udarno oštećenje (prskanje matrice, lom vlakna i delaminacija), što zavisi od brojnih uticajnih parametara. U radu je predstavljen i tzv. „multiscale“ pristup modeliranju oštećenja i navedeni su kriterijumi otkaza kompozitnih laminata. Razmotreni su numeričko modeliranje udara, tranzijentna dinamička analiza i opisani postojeći modeli udara po Abrate-u, kao i oni iz softvera LS-DYNA. Prikazan je MATLAB softver za analizu otkaza laminata i dat kod za izračunavanje A, B i D matrica krutosti određenog kompozitnog laminata. Navedeni su i objašnjeni najznačajniji softveri za analizu udara. Takođe teza sadrži opis i prikaz rezultata modeliranja udara projektila u ojačanu ploču od karbonskog vlakna u programu ABAQUS. Istovremeno, izvršena je numerička analiza i simulacija udara u ploču i aeroprofil od kompozitnog laminata T300/914, pod dejstvom određenog udarnog (pritisnog) opterećenja u specijalizovanom programu Pro/Engineer...In the doctoral thesis the problem of modeling of impact damage in laminated composite structures has discussed. Impact in certain structures causing damage, whose characterization is extremely demanding and complex. There are analytical, experimental and numerical approaches to the analysis of mechanisms for the onset and development of these defects. Thereby it is necessary to estimate the resistance on occurrence and tolerance to already existing impact damage. All developed models of impact damage, with a certain accuracy, approximate impact caused damage (matrix cracking, fiber fracture and delamination), which depends on a number of influential parameters. The paper introduces the so-called "multiscale" approach to the modeling of damage and failure criteria for composite laminates are listed. Numerical modeling of impact, transient dynamic analysis of existing models and described Abrate impact models, as they from LS-DYNA software were discussed. MATLAB software for failure analysis of the laminate is presented and the code for calculation of A, B and D stiffness matrix of certain composite laminate is given. The most important software for the impact analysis are listed and explained. Also thesis contains a description and presentation results of impact modeling in the carbon fiber reinforced plate in software ABAQUS. At the same time, numerical analysis and simulation of impact on the plate and airfoil from composite laminate T300/914, under the influence of a certain impact (compressive) load in a specialized program Pro/Engineer was performed

Tensile behaviour of polyethylene under different loading rates in the presence of imperfections

This paper highlights the changes of polyethylene behaviour during various loading rates. The experimental programme was carried out on samples taken from PE80 polyethylene gas pipes with simulated imperfections with bilateral V-notch, U-notch and central hole. The hybrid technique tensile test - infrared test was used for examining the fracture behaviour of PE80 thermoplastic material samples under different loading rates. Correlation between the loading rate and tensile strength of polyethylene has been established. It has been shown that tensile strength varies with loading rate according to a logarithmic law. Also, it was shown that viscoelastic-plastic character of the polymer material influences directly the specific response of material to loading rates

Tensile behaviour of polyethylene under different loading rates in the presence of imperfections

This paper highlights the changes of polyethylene behaviour during various loading rates. The experimental programme was carried out on samples taken from PE80 polyethylene gas pipes with simulated imperfections with bilateral V-notch, U-notch and central hole. The hybrid technique tensile test - infrared test was used for examining the fracture behaviour of PE80 thermoplastic material samples under different loading rates. Correlation between the loading rate and tensile strength of polyethylene has been established. It has been shown that tensile strength varies with loading rate according to a logarithmic law. Also, it was shown that viscoelastic-plastic character of the polymer material influences directly the specific response of material to loading rates

The usage of 3D printing in the analysis of the product design: Case: Electronic enclosure of compact pressure transmitter

Aditivna proizvodnja uključuje izradu proizvoda složene geometrije u relativno malim količinama, kao i izradu alata i kalupa za masovnu proizvodnju. Aditivnom proizvodnjom realizuju se modeli prema digitalnom prikazu, a primena je ogromna u različitim industrijskim sektorima. U poređenju sa tradicionalnom proizvodnjom, glavni parametri u odabiru aditivne tehnologije su: ušteda energije, smanjenje otpada, smanjenje upotrebe većeg broja alata, kao i optimizacija dizajna. Aditivna proizvodnja ili tehnologija 3D štampe rade na principu dodavanja materijala u slojevima, tj. model se formira od slojeva rastopljenog materijala koji se odmah hladi i očvršćava. 3D štampa omogućava čestu i jednostavnu modifikaciju modela na zahtev kupca, a pre ulaska modela u samu proizvodnju. Ovo čini komunikaciju na relaciji proizvođač-kupac dosta jednostavnom. Polazni materijal za izradu modela je polilaktična kiselina (PLA). To je ekološki termoplastični poliester koji se prirodno razgrađuje u prirodi. Na mehaničke karakteristike realizovanog modela od PLA značajno utiču različite tehnološke promenljive kao što su: prečnik brizgaljke, debljina definisanog sloja, procentualna vrednost ispune, veličina uzorka koji se puni, brzina punjenja i temperatura proizvodnje. Cilj ovog rada je da se prikaže postupak realizacije kutije elektronike za malogabaritni transmiter pritiska na 3D štampaču. Time se projektantu daje mogućnost da ispravi postojeće greške, modifikuje proizvod prema zahtevima krajnjih korisnika i na kraju daje polazna osnova za realizaciju prototipa novog proizvoda.Additive manufacturing involves manufacturing of products with complex geometry in relatively small quantities, as well as the tools and molds manufacturing for mass production. With additive manufacturing, digital models are being realized and implementation is huge in various industrial sectors. Compared to traditional manufacturing, the main parameters in the choice of additive technology are: energy savings, waste reduction, reduced use of more tools and optimization of design. Additive manufacturing or 3D printing technology works on the principle of adding material in layers, i.e. the model is formed from layers of molten material that is immediately cooled and solidified. 3D printing allows to work with customers to solve design problems before embarking on a launch production. The starting material for the model is polyactic acid (PLA). It is an eco-friendly thermoplastic polyester, that breaks down naturally. The mechanical characteristics of the realized PLA model are significantly influenced by various technological variables, such as following: nozzle diameter, thickness of defined layer, percentage of fill, sample size to be filled, filling rate and production temperature. The aim of this paper is to present the process of realization of an electronics enclosure for a compact pressure transmitter on a 3D printer. This gives the designer the possibility to correct existing errors, modify the product according to the wishes of the end users and finally provides a starting point for the prototype of new product

The usage of 3D printing in the analysis of the product design: Case – Electronic enclosure of compact pressure transmitter

Aditivna proizvodnja uključuje izradu proizvoda složene geometrije u relativno malim količinama, kao i izradu alata i kalupa za masovnu proizvodnju. Aditivnom proizovnjom realizuju se modeli prema digitalnom prikazu, a primena je ogromna u različitim industrijskim sektorima. U poređenju sa tradicionalnom proizvodnjom, glavni parametri u odabiru aditivne tehnologije su: ušteda energije, smanjenje otpada, smanjenje upotrebe većeg broja alata, kao i optimizacija dizajna. Aditivna proizvodnja ili tehnologija 3D štampe rade na principu dodavanja materijala u slojevima, tj. model se formira od slojeva rastopljenog materijala koji se odmah hladi i očvršćava. 3D štampa omogućava čestu i jednostavnu modifikaciju modela na zahtev kupca, a pre ulaska modela u samu proizvodnju. Ovo čini komunikaciju na relaciji proizvođač-kupac dosta jednostavnom. Polazni materijal za izradu modela je polilaktična kiselina (PLA). To je ekološki termoplastični poliester koji se prirodno razgrađuje u prirodi. Na mehaničke karakteristike realizovanog modela od PLA značajno utiču različite tehnološke promenljive kao što su: prečnik brizgaljke, debljina definisanog sloja, procentualna vrednost ispune, veličina uzorka koji se puni, brzina punjenja i temperatura proizvodnje. Cilj ovog rada je da se prikaže postupak realizacije kutije elektronike za malogabaritni transmiter pritiska na 3D štampaču. Time se projektantu daje mogućnost da ispravi postojeće greške, modifikuje proizvod prema zahterima krajnjih korisnika i na kraju daje polazna osnova za realizaciju prototipa novog proizvoda.Additive manufacturing involves manufacturing of products with complex geometry in relatively small quantities, as well as the tools and molds manufacturing for mass production. With additive manufacturing, digital models are being realized and implementation is huge in various industrial sectors. Compared to traditional manufacturing, the main parameters in the choice of additive technology are: energy savings, waste reduction, reduced use of more tools and optimization of design. Additive manufacturing or 3D printing technology works on the principle of adding material in layers, i.e. the model is formed from layers of molten material that is immediately cooled and solidified. 3D printing allows to work with customers to solve design problems before embarking on a launch production. The starting material for the model is polyactic acid (PLA). It is an eco-friendly thermoplastic polyester, that breaks down naturally. The mechanical characteristics of the realized PLA model are significantly influenced by various technological variables, such as following: nozzle diameter, thickness of defined layer, percentage of fill, sample size to be filled, filling rate and production temperature. The aim of this paper is to present the process of realization of an electronics enclosure for a compact pressure transmitter on a 3D printer. This gives the designer the possibility to correct existing errors, modify the product according to the wishes of the end users and finally provides a starting point for the prototype of new product

Modeling of impact damage in laminate composite structures

U doktorskoj tezi razmatran je problem modeliranja udarnih oštećenja u laminiranim kompozitnim strukturama. Udari u određene strukture uzrokuju oštećenja, čija je karakterizacija ekstremno zahtevna i složena. Postoje analitički, eksperimentalni i numerički pristupi analize mehanizama nastanka i razvoja tih oštećenja. Pri tome neophodno je proceniti otpor na nastanak i toleranciju već prisutnog udarnog oštećenja. Svi razvijeni modeli udarnih oštećenja, sa određenom tačnošću, aproksimiraju nastalo udarno oštećenje (prskanje matrice, lom vlakna i delaminacija), što zavisi od brojnih uticajnih parametara. U radu je predstavljen i tzv. „multiscale“ pristup modeliranju oštećenja i navedeni su kriterijumi otkaza kompozitnih laminata. Razmotreni su numeričko modeliranje udara, tranzijentna dinamička analiza i opisani postojeći modeli udara po Abrate-u, kao i oni iz softvera LS-DYNA. Prikazan je MATLAB softver za analizu otkaza laminata i dat kod za izračunavanje A, B i D matrica krutosti određenog kompozitnog laminata. Navedeni su i objašnjeni najznačajniji softveri za analizu udara. Takođe teza sadrži opis i prikaz rezultata modeliranja udara projektila u ojačanu ploču od karbonskog vlakna u programu ABAQUS. Istovremeno, izvršena je numerička analiza i simulacija udara u ploču i aeroprofil od kompozitnog laminata T300/914, pod dejstvom određenog udarnog (pritisnog) opterećenja u specijalizovanom programu Pro/Engineer...In the doctoral thesis the problem of modeling of impact damage in laminated composite structures has discussed. Impact in certain structures causing damage, whose characterization is extremely demanding and complex. There are analytical, experimental and numerical approaches to the analysis of mechanisms for the onset and development of these defects. Thereby it is necessary to estimate the resistance on occurrence and tolerance to already existing impact damage. All developed models of impact damage, with a certain accuracy, approximate impact caused damage (matrix cracking, fiber fracture and delamination), which depends on a number of influential parameters. The paper introduces the so-called "multiscale" approach to the modeling of damage and failure criteria for composite laminates are listed. Numerical modeling of impact, transient dynamic analysis of existing models and described Abrate impact models, as they from LS-DYNA software were discussed. MATLAB software for failure analysis of the laminate is presented and the code for calculation of A, B and D stiffness matrix of certain composite laminate is given. The most important software for the impact analysis are listed and explained. Also thesis contains a description and presentation results of impact modeling in the carbon fiber reinforced plate in software ABAQUS. At the same time, numerical analysis and simulation of impact on the plate and airfoil from composite laminate T300/914, under the influence of a certain impact (compressive) load in a specialized program Pro/Engineer was performed