Milorad Zrilić - Academia.edu (original) (raw)

Papers by Milorad Zrilić

Zavarivanje i zavarene konstrukcije, 2017

Composites Part B-engineering, 2017

In this study carbon nanotubes (CNT) and silica nanoparticles (SiO 2) were added to enhance the d... more In this study carbon nanotubes (CNT) and silica nanoparticles (SiO 2) were added to enhance the dynamic mechanical and anti-stabbing properties of the polyurethane/p-aramid multiaxial fabric (Kolon fabric) composites for ballistic protection. The SiO 2 were modified (mSiO 2) and CNT were oxidised (o-CNT) in order to fabricate o-CNT/mSiO 2 hybrid nanoparticles. Various kinds of nanoreinforcement particles were added into poly (vinyl butyral) (PVB)/ethanol solution. The results revealed that the films PVB/o-MWCNT/mSiO 2 and PVB/o-SWCNT/mSiO 2 yielded 101% and 141% improvement in indentation hardness together with 89% and 117% improvement in reduced elastic modulus, respectively, compared to the neat PVB film. The experiments demonstrated that the Kolon/PVB/o-SWCNT/mSiO 2 fabric sample yielded 35% improvement in absorbed energy and 50% improvement in the storage modulus compared to the Kolon/ PVB sample.

Journal of Solution Chemistry, Jan 27, 2011

The osmotic coefficients of K2HPO4(aq) have been measured at T=298.15 K by the isopiestic vapor p... more The osmotic coefficients of K2HPO4(aq) have been measured at T=298.15 K by the isopiestic vapor pressure method over the range of molalities from 1.3846 mol⋅kg−1 to 13.939 mol⋅kg−1 (oversaturation) with CaCl2(aq) as the reference solution. The molalities and osmotic coefficients of saturated solutions in equilibrium with K2HPO4⋅xH2O(cr) were measured simultaneously by the same method. Available literature osmotic coefficients of K2HPO4(aq) at

International Journal of Polymer Science, 2015

This study investigates a wide range of clinically relevant mechanical properties of poly(methyl ... more This study investigates a wide range of clinically relevant mechanical properties of poly(methyl methacrylate) (PMMA) denture base materials modified with di-methyl itaconate (DMI) and din -butyl itaconate (DBI) in order to compare them to a commercial PMMA denture base material. The commercial denture base formulation was modified with DMI and DBI by replacing up to 10 wt% of methyl methacrylate (MMA) monomer. The specimens were prepared by standard bath curing process. The influence of the itaconate content on hardness, impact strength, tensile, and thermal and dynamic mechanical properties was investigated. It is found that the addition of din -alkyl itaconates gives homogenous blends that show decreased glass transition temperature, as well as decrease in storage modulus, ultimate tensile strength, and impact fracture resistance with increase in the itaconate content. The mean values of surface hardness show no significant change with the addition of itaconates. The magnitude of the measured values indicates that the poly(methyl methacrylate) (PMMA) denture base material modified with itaconates could be developed into a less toxic, more environmentally and patient friendly product than commercial pure PMMA denture base material.

Scientific Technical Review, 2014

This paper presents the results of the laser cleaning effects on textile samples with corroded me... more This paper presents the results of the laser cleaning effects on textile samples with corroded metallic threads. In many museum collections, there are textile exhibits like uniforms, national costumes, flags and home textile, embroidered with metallic threads. Corrosion of metal threads is one of the most common problems that damage embroidered items. In the practice, the application of conventional cleaning methods rarely gives the expected results, and the implementation of laser technology was the next step for corrosion products cleaning. The Nd:YAG laser was used to clean the corrosion of embroidered items from a museum study collection. The effects on the laser irradiated zones were investigated by optical and SEM microscopy and the EDX analysis. The laser irradiation process parameters of the metal threads corrosion

Russian Journal of Physical Chemistry A, Dec 1, 2011

The solubility in the ternary system, aqueous mixture of CaSO4 and Na2SO4, at T = 298.15 K compri... more The solubility in the ternary system, aqueous mixture of CaSO4 and Na2SO4, at T = 298.15 K comprises five different salts: calcium sulfate dihydrate, mirabilite, thenardite, glauberite and labile salt. Using the Extended Pitzer’s Ion Interaction model for pure and mixed electrolyte solutions and criteria of phase equilibria, predicted solubility behavior of salts was compared with experimental results from literature. The agreement between calculated and experimental solubilities was excellent in the ionic strength range up to 10.9062 mol kg−1.

Journal of Biomedical Materials Research Part B, Jun 7, 2013

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HA... more This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph Si), whiskers (Wh), silicon-doped whiskers (Wh Si), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph Si groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon-doping have a potential to be part of the filler content of dental composites. V

Materials Letters, May 1, 2012

ABSTRACT In this study, spherical particles of hydroxyapatite (HA) and α-tricalcium phosphate (α-... more ABSTRACT In this study, spherical particles of hydroxyapatite (HA) and α-tricalcium phosphate (α-Ca3(PO4)2; α-TCP) doped with different amounts of silicon were used for the preparation of scaffolds. The scaffolds were obtained by a replica foam method using particles of narrow size distribution pre-annealed at 1150 °C with different α-TCP and HA contents in order to investigate the effect of composition on their morphological and mechanical properties. Morphology, size, and distribution of the particles were characterized using scanning electron microscopy and particle size analyzer. The obtained α-TCP-HA scaffolds had compressive strengths up to 5.7 MPa with a uniform and interconnected porous structure. X-ray diffraction analysis used to determine the crystal structure of the scaffolds confirmed that the α-TCP-HA content could be controlled by the amount of silicon ions.

Clinical Oral Investigations, Nov 15, 2013

The aims of this study were to evaluate the radiopacity, compressive strength, setting time, and ... more The aims of this study were to evaluate the radiopacity, compressive strength, setting time, and porosity of white Portland cement (PC) with the addition of bismuth oxide (Bi2O3), zirconium dioxide (ZrO2), and ytterbium trifluoride (YbF3) after immersion at 37 °C for 7 days in distilled water or phosphate buffer saline. Specimens measuring 8 mm in diameter and 1 mm in thickness were fabricated from PC with the addition of 10, 20, and 30 wt% Bi2O3, ZrO2 or YbF3. ProRoot MTA (Dentsply, Tulsa, OK, USA) and pure PC were used as controls. For radiopacity assessments, specimens were radiographed alongside a tooth slices and an aluminum stepwedge on Extraspeed occlusal dental films (Insight Kodak, Rochester, New York). Mean optical density of each specimen was calculated and used to express radiopacity of the material as an equivalent thickness of aluminum. Compressive strength was measured by using 4-mm diameter and 6-mm high specimens and Universal testing machine. High-pressure mercury intrusion porosimeter (Carlo Erba Porosimeter 2000) was employed to measure the porosity of the specimens. The setting time was measured by using a needle of 100 g in weight. The morphology of specimens was evaluated using a scanning electron microscope (TESCAN Mira3 XMU, USA Inc.). Data were analyzed by one-way ANOVA and post hoc Tukey test (P < 0.05). The PC with the addition of at least 10 wt% Bi2O3 and 20 wt% ZrO2 or YbF3 demonstrated greater radiopacity value than the recommended 3 mmAl cut-off. ZrO2 and YbF3 increased the compressive strength of PC, but it was not statistically significant (P > 0.05), while Bi2O3 decreased it (P < 0.05). All radiopacifiers significantly increased the porosity of the experimental cements (P < 0.05). Bi2O3 extended the setting time of PC (P < 0.05), whilst ZrO2 and YbF3 did not significantly affect it (P > 0.05). ZrO2 and YbF3 may be used as a suitable alternative to replace Bi2O3 in MTA without influencing its physical properties.

Materials, Apr 21, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Procedia structural integrity, 2018

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Metalurgija, 2014

The post weld heat treatment (PWHT) was used to reduce the level of the residual stresses and inc... more The post weld heat treatment (PWHT) was used to reduce the level of the residual stresses and increase of the crack resistance of the materal in the cnnection part. The article presents the results of the residual stress measurements immediately after welding and after the stress relaxation by the PWHT.

Procedia structural integrity, 2018

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Springer eBooks, 2020

This research considers a possibility of improving the impact and ballistic resistance of composi... more This research considers a possibility of improving the impact and ballistic resistance of composite materials based on aramid fabric impregnated with poly (vinyl butyral), PVB, with the application of multi-layer inorganic nanotubes of tungsten disulfide (INT-WS2) as the reinforcement. Multi-layered nano-structures of tungsten disulfide are known by their excellent mechanical resistance, especially shock absorbing properties, which promote their use as a reinforcement in composite materials. INT-WS2 used in this research were observed using scanning electron microscope and the obtained images were analyzed in program Image Pro Plus. Before the application in the composite they were ultrasonically deagglomerated. Ballistic composites were prepared impregnating the aramid fabric with system PVB/INT-WS2 and by pressing defined number of layers under high pressure and defined temperature. Charpy impact test, ballistic shooting with two different ammunition calibers and stab resistance test with controlled knife penetration were performed on prepared composite samples, and resulted in significant improvements for samples with nano-reinforcement regarding the absorbed energy of impact, toughness and the ballistic resistance.

Polymer Composites, Jul 8, 2013

This article presents research on the influence of a coupling agent c-methacryloxypropyltrimethox... more This article presents research on the influence of a coupling agent c-methacryloxypropyltrimethoxysilane (MEMO) and cross-linking agent dicumyl peroxide (DCP) on thermal and nanomechanical properties of neat and waste polyethylene (WPE) as well as their blend. Modification of nanosilica by silanization was performed under supercritical conditions of carbon dioxide-ethanol mixture. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), indentation as well as scratch testing at nanoscale were employed for characterization of the polymer matrix with unmodified and modified nano-SiO 2 particles. Low amounts of the peroxide and silanized nano-SiO 2 particles in the composite formulation significantly improved thermal and tribo-mechanical behavior at nanoscale.

In the paper, the level of damage of steam pipeline steel after about 100,000 hours at 540°C (100... more In the paper, the level of damage of steam pipeline steel after about 100,000 hours at 540°C (1004 °F) under pressure of 42 bars (609 PSI) is analyzed. Material degradation is estimated using a combined experimental and numerical procedure based on micromechanical or local approach to fracture. Detailed analysis is conducted on the samples taken from exploited – used steel and from unused – new steel of the same designation. Damage parameter – void growth ratio – is determined using round notched specimens, (including various notch radii). A comparison of the values for critical void growth ratio, computed for tested steels is made. Based on the values obtained, the possibility of prolongation of the operating life of used steel is discussed.

DOAJ (DOAJ: Directory of Open Access Journals), 2007

Tekstilna industrija, 2004

Developments in technology and daily needs have inevitably led to the appearance of new market-ba... more Developments in technology and daily needs have inevitably led to the appearance of new market-based products or in the implementation of new raw materials for the manufacture of such products. The levels of daily needs and consumer demands and total investments in ...

FME Transactions, 2012

For a wide range of engineering structures such as ceramics, porous shape memory alloys, foam-lik... more For a wide range of engineering structures such as ceramics, porous shape memory alloys, foam-like structures and thermal spray deposits, porous materials have been used. Recently, porous biocomposites for the applications to bone implants and hard tissue engineering have become increasingly important. The effect of matrix porosity on the elastic properties of particulate biocomposite was studied by two-and three-phase unit cell finite element models. A 3D FCC unit cell model of particulate composite with included matrix porosity is developed and compared with the simple theoretical models. It is found that the matrix porosity has noticeable influence on the composite elastic properties. The two-phase predictions overestimate the three-phase ones because of the physical threshold for three-phase model determined by the particle content.

Zavarivanje i zavarene konstrukcije, 2017

Composites Part B-engineering, 2017

In this study carbon nanotubes (CNT) and silica nanoparticles (SiO 2) were added to enhance the d... more In this study carbon nanotubes (CNT) and silica nanoparticles (SiO 2) were added to enhance the dynamic mechanical and anti-stabbing properties of the polyurethane/p-aramid multiaxial fabric (Kolon fabric) composites for ballistic protection. The SiO 2 were modified (mSiO 2) and CNT were oxidised (o-CNT) in order to fabricate o-CNT/mSiO 2 hybrid nanoparticles. Various kinds of nanoreinforcement particles were added into poly (vinyl butyral) (PVB)/ethanol solution. The results revealed that the films PVB/o-MWCNT/mSiO 2 and PVB/o-SWCNT/mSiO 2 yielded 101% and 141% improvement in indentation hardness together with 89% and 117% improvement in reduced elastic modulus, respectively, compared to the neat PVB film. The experiments demonstrated that the Kolon/PVB/o-SWCNT/mSiO 2 fabric sample yielded 35% improvement in absorbed energy and 50% improvement in the storage modulus compared to the Kolon/ PVB sample.

Journal of Solution Chemistry, Jan 27, 2011

The osmotic coefficients of K2HPO4(aq) have been measured at T=298.15 K by the isopiestic vapor p... more The osmotic coefficients of K2HPO4(aq) have been measured at T=298.15 K by the isopiestic vapor pressure method over the range of molalities from 1.3846 mol⋅kg−1 to 13.939 mol⋅kg−1 (oversaturation) with CaCl2(aq) as the reference solution. The molalities and osmotic coefficients of saturated solutions in equilibrium with K2HPO4⋅xH2O(cr) were measured simultaneously by the same method. Available literature osmotic coefficients of K2HPO4(aq) at

International Journal of Polymer Science, 2015

This study investigates a wide range of clinically relevant mechanical properties of poly(methyl ... more This study investigates a wide range of clinically relevant mechanical properties of poly(methyl methacrylate) (PMMA) denture base materials modified with di-methyl itaconate (DMI) and din -butyl itaconate (DBI) in order to compare them to a commercial PMMA denture base material. The commercial denture base formulation was modified with DMI and DBI by replacing up to 10 wt% of methyl methacrylate (MMA) monomer. The specimens were prepared by standard bath curing process. The influence of the itaconate content on hardness, impact strength, tensile, and thermal and dynamic mechanical properties was investigated. It is found that the addition of din -alkyl itaconates gives homogenous blends that show decreased glass transition temperature, as well as decrease in storage modulus, ultimate tensile strength, and impact fracture resistance with increase in the itaconate content. The mean values of surface hardness show no significant change with the addition of itaconates. The magnitude of the measured values indicates that the poly(methyl methacrylate) (PMMA) denture base material modified with itaconates could be developed into a less toxic, more environmentally and patient friendly product than commercial pure PMMA denture base material.

Scientific Technical Review, 2014

This paper presents the results of the laser cleaning effects on textile samples with corroded me... more This paper presents the results of the laser cleaning effects on textile samples with corroded metallic threads. In many museum collections, there are textile exhibits like uniforms, national costumes, flags and home textile, embroidered with metallic threads. Corrosion of metal threads is one of the most common problems that damage embroidered items. In the practice, the application of conventional cleaning methods rarely gives the expected results, and the implementation of laser technology was the next step for corrosion products cleaning. The Nd:YAG laser was used to clean the corrosion of embroidered items from a museum study collection. The effects on the laser irradiated zones were investigated by optical and SEM microscopy and the EDX analysis. The laser irradiation process parameters of the metal threads corrosion

Russian Journal of Physical Chemistry A, Dec 1, 2011

The solubility in the ternary system, aqueous mixture of CaSO4 and Na2SO4, at T = 298.15 K compri... more The solubility in the ternary system, aqueous mixture of CaSO4 and Na2SO4, at T = 298.15 K comprises five different salts: calcium sulfate dihydrate, mirabilite, thenardite, glauberite and labile salt. Using the Extended Pitzer’s Ion Interaction model for pure and mixed electrolyte solutions and criteria of phase equilibria, predicted solubility behavior of salts was compared with experimental results from literature. The agreement between calculated and experimental solubilities was excellent in the ionic strength range up to 10.9062 mol kg−1.

Journal of Biomedical Materials Research Part B, Jun 7, 2013

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HA... more This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph Si), whiskers (Wh), silicon-doped whiskers (Wh Si), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph Si groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon-doping have a potential to be part of the filler content of dental composites. V

Materials Letters, May 1, 2012

ABSTRACT In this study, spherical particles of hydroxyapatite (HA) and α-tricalcium phosphate (α-... more ABSTRACT In this study, spherical particles of hydroxyapatite (HA) and α-tricalcium phosphate (α-Ca3(PO4)2; α-TCP) doped with different amounts of silicon were used for the preparation of scaffolds. The scaffolds were obtained by a replica foam method using particles of narrow size distribution pre-annealed at 1150 °C with different α-TCP and HA contents in order to investigate the effect of composition on their morphological and mechanical properties. Morphology, size, and distribution of the particles were characterized using scanning electron microscopy and particle size analyzer. The obtained α-TCP-HA scaffolds had compressive strengths up to 5.7 MPa with a uniform and interconnected porous structure. X-ray diffraction analysis used to determine the crystal structure of the scaffolds confirmed that the α-TCP-HA content could be controlled by the amount of silicon ions.

Clinical Oral Investigations, Nov 15, 2013

The aims of this study were to evaluate the radiopacity, compressive strength, setting time, and ... more The aims of this study were to evaluate the radiopacity, compressive strength, setting time, and porosity of white Portland cement (PC) with the addition of bismuth oxide (Bi2O3), zirconium dioxide (ZrO2), and ytterbium trifluoride (YbF3) after immersion at 37 °C for 7 days in distilled water or phosphate buffer saline. Specimens measuring 8 mm in diameter and 1 mm in thickness were fabricated from PC with the addition of 10, 20, and 30 wt% Bi2O3, ZrO2 or YbF3. ProRoot MTA (Dentsply, Tulsa, OK, USA) and pure PC were used as controls. For radiopacity assessments, specimens were radiographed alongside a tooth slices and an aluminum stepwedge on Extraspeed occlusal dental films (Insight Kodak, Rochester, New York). Mean optical density of each specimen was calculated and used to express radiopacity of the material as an equivalent thickness of aluminum. Compressive strength was measured by using 4-mm diameter and 6-mm high specimens and Universal testing machine. High-pressure mercury intrusion porosimeter (Carlo Erba Porosimeter 2000) was employed to measure the porosity of the specimens. The setting time was measured by using a needle of 100 g in weight. The morphology of specimens was evaluated using a scanning electron microscope (TESCAN Mira3 XMU, USA Inc.). Data were analyzed by one-way ANOVA and post hoc Tukey test (P < 0.05). The PC with the addition of at least 10 wt% Bi2O3 and 20 wt% ZrO2 or YbF3 demonstrated greater radiopacity value than the recommended 3 mmAl cut-off. ZrO2 and YbF3 increased the compressive strength of PC, but it was not statistically significant (P > 0.05), while Bi2O3 decreased it (P < 0.05). All radiopacifiers significantly increased the porosity of the experimental cements (P < 0.05). Bi2O3 extended the setting time of PC (P < 0.05), whilst ZrO2 and YbF3 did not significantly affect it (P > 0.05). ZrO2 and YbF3 may be used as a suitable alternative to replace Bi2O3 in MTA without influencing its physical properties.

Materials, Apr 21, 2023

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Procedia structural integrity, 2018

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Metalurgija, 2014

The post weld heat treatment (PWHT) was used to reduce the level of the residual stresses and inc... more The post weld heat treatment (PWHT) was used to reduce the level of the residual stresses and increase of the crack resistance of the materal in the cnnection part. The article presents the results of the residual stress measurements immediately after welding and after the stress relaxation by the PWHT.

Procedia structural integrity, 2018

During their operation, modern aircraft engine components are subjected to increasingly demanding... more During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.

Springer eBooks, 2020

This research considers a possibility of improving the impact and ballistic resistance of composi... more This research considers a possibility of improving the impact and ballistic resistance of composite materials based on aramid fabric impregnated with poly (vinyl butyral), PVB, with the application of multi-layer inorganic nanotubes of tungsten disulfide (INT-WS2) as the reinforcement. Multi-layered nano-structures of tungsten disulfide are known by their excellent mechanical resistance, especially shock absorbing properties, which promote their use as a reinforcement in composite materials. INT-WS2 used in this research were observed using scanning electron microscope and the obtained images were analyzed in program Image Pro Plus. Before the application in the composite they were ultrasonically deagglomerated. Ballistic composites were prepared impregnating the aramid fabric with system PVB/INT-WS2 and by pressing defined number of layers under high pressure and defined temperature. Charpy impact test, ballistic shooting with two different ammunition calibers and stab resistance test with controlled knife penetration were performed on prepared composite samples, and resulted in significant improvements for samples with nano-reinforcement regarding the absorbed energy of impact, toughness and the ballistic resistance.

Polymer Composites, Jul 8, 2013

This article presents research on the influence of a coupling agent c-methacryloxypropyltrimethox... more This article presents research on the influence of a coupling agent c-methacryloxypropyltrimethoxysilane (MEMO) and cross-linking agent dicumyl peroxide (DCP) on thermal and nanomechanical properties of neat and waste polyethylene (WPE) as well as their blend. Modification of nanosilica by silanization was performed under supercritical conditions of carbon dioxide-ethanol mixture. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), indentation as well as scratch testing at nanoscale were employed for characterization of the polymer matrix with unmodified and modified nano-SiO 2 particles. Low amounts of the peroxide and silanized nano-SiO 2 particles in the composite formulation significantly improved thermal and tribo-mechanical behavior at nanoscale.

In the paper, the level of damage of steam pipeline steel after about 100,000 hours at 540°C (100... more In the paper, the level of damage of steam pipeline steel after about 100,000 hours at 540°C (1004 °F) under pressure of 42 bars (609 PSI) is analyzed. Material degradation is estimated using a combined experimental and numerical procedure based on micromechanical or local approach to fracture. Detailed analysis is conducted on the samples taken from exploited – used steel and from unused – new steel of the same designation. Damage parameter – void growth ratio – is determined using round notched specimens, (including various notch radii). A comparison of the values for critical void growth ratio, computed for tested steels is made. Based on the values obtained, the possibility of prolongation of the operating life of used steel is discussed.

DOAJ (DOAJ: Directory of Open Access Journals), 2007

Tekstilna industrija, 2004

Developments in technology and daily needs have inevitably led to the appearance of new market-ba... more Developments in technology and daily needs have inevitably led to the appearance of new market-based products or in the implementation of new raw materials for the manufacture of such products. The levels of daily needs and consumer demands and total investments in ...

FME Transactions, 2012

For a wide range of engineering structures such as ceramics, porous shape memory alloys, foam-lik... more For a wide range of engineering structures such as ceramics, porous shape memory alloys, foam-like structures and thermal spray deposits, porous materials have been used. Recently, porous biocomposites for the applications to bone implants and hard tissue engineering have become increasingly important. The effect of matrix porosity on the elastic properties of particulate biocomposite was studied by two-and three-phase unit cell finite element models. A 3D FCC unit cell model of particulate composite with included matrix porosity is developed and compared with the simple theoretical models. It is found that the matrix porosity has noticeable influence on the composite elastic properties. The two-phase predictions overestimate the three-phase ones because of the physical threshold for three-phase model determined by the particle content.