The Experts below are selected from a list of 20850 Experts worldwide ranked by ideXlab platform
J Kargerkocsis - One of the best experts on this subject based on the ideXlab platform.
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modification of vinyl ester and vinyl ester urethane resin based bulk molding compounds bmc with acrylated epoxidized soybean and linseed oils
2012Co-Authors: S. Grishchuk, J KargerkocsisAbstract:Acrylated epoxidized soybean and linseed oils of different characteristics were incorporated in the absence and presence of polymeric methylene diphenyl isocyanate (PMDI) in a vinyl ester (VE) resin-based bulk molding compound (BMC) up to 15 wt% (with respect to VE resin). The thermal, thermo-mechanical, Static Fracture mechanical, dynamic impact (Charpy), and thermal degradation properties of the BMC compounds were determined. With increasing amount of functionalized plant oils the glass transition temperature (T g) of the matrix, the stiffness (E modulus) and Charpy impact strength of the BMCs decreased. The Static Fracture toughness was slightly increased and the Fracture energy remained unaffected by the modification with increasing amount of oil. Additional crosslinking of VE, induced by PMDI, markedly enhanced the T g but yielded a large drop in the glassy modulus. This finding was traced to resin dilution and to unfavored PMDI/kaolin interactions triggered by the water content of the latter. The thermal degradation of the BMCs was less affected, however, their degradation started earlier for the modifications either with functionalized plant oil or PMDI. Dilution of VE-based BMCs with acrylated epoxidized plant oils requires reworking of the corresponding recipes to keep the property degradation limited.
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greening of unsaturated polyester resin based bulk molding compound with acrylated epoxidized soybean and linseed oils effect of urethane hybridization
2011Co-Authors: S. Grishchuk, J Kargerkocsis, R Leanza, P KirchnerAbstract:Acrylated epoxidized soybean and linseed oils of different characteristics were incorporated in the absence and presence of PMDI in UP resin-based BMC up to 15 wt%. The thermal, thermomechanical, Static Fracture mechanical, dynamic impact, and thermal degradation properties of the modified and reference BMCs were determined. With increasing amount of functionalized plant oils, the glass transition temperature of the matrix, the stiffness (E-modulus), and Charpy impact strength of the composites decreased. On the other hand, the Static Fracture mechanical parameters and thermal degradation were less affected by oil modification. Type and characteristics of the plant oils affected mostly the Charpy impact strength. Additional cross-linking, induced by PMDI, resulted in some compensation of the property deterioration except the glassy modulus. The large drop in the modulus was traced to unfavored PMDI/kaolin interactions triggered by the water content of the latter. Incorporation of PMDI was associated with ...
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relationship between morphology and mechanical properties of polypropylene ethene co butene binary blends with various butene contents
2000Co-Authors: D E Mouzakis, D Mader, Rolf Mulhaupt, J KargerkocsisAbstract:A metallocene-based isotactic polypropylene (m-iPP) was blended with various types of ethene-co-butene rubbers (EBR). Blend miscibility was examined by means of dynamic mechanical analysis (DMTA). In addition, morphology was studied on cyclohexane etched cryoFractured samples. Stiffness and toughness properties were assessed and interpreted in function of the blend miscibility. Izod tests served for the dynamic Fracture toughness characterization. The essential work of Fracture (EWF) approach was used for the characterization of the Static Fracture toughness. It was found that the 1-butene content of the EBR strongly affects the blend miscibility. A disperse structure was found as prerequisite for outstanding overall toughness. When distiguishing between resistance to crack initiation and propagation, it was found that they are changing adversely to one another.
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Fracture behaviour and damage growth in knitted carbon fibre fabric reinforced polyethylmethacrylate
1996Co-Authors: J Kargerkocsis, Tibor Czigány, Jacqueline MayeAbstract:The Static Fracture and the damage zone growth in weft knitted carbon fibre (CF) fabric reinforced thermoplastic polyethylmethacrylate have been studied on tensile loaded, single edge notched specimens at room temperature. It was established that the Fracture toughness increases with increasing number of reinforcing knit plies incorporated. This was attributed to a more homogeneous distribution of the reinforcing knit fabrics in the matrix ; this can also be considered as a reduction of the apparent mesh size of the knits. The size of the damage zone was estimated from the location of the acoustic emission (AE) events and from infrared thermography ( IT). The AE technique indicated a much bigger damage zone than IT for single layer weft knitted fabric reinforced composites. However, the damage zone size and shape derived from AE and IT agreed very well with one another for composites with multiple CF knit reinforcement, for which the diameter of the circular damage zone was found to be 15-20 mm. This indicates that the width of specimens must be greater than ∼20 mm to achieve accurate mechanical data.
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microstructural aspects of Fracture and fatigue behavior in short fiber reinforced injection molded pps peek and pen composites
1991Co-Authors: J KargerkocsisAbstract:Both the Fracture and fatigue behavior of temperature-resistant thermoplastic matrix composites with discontinuous fiber reinforcement are strongly affected by the microstructure. The molding-induced microstructure of the composites can be characterized by a reinforcing effectiveness parameter (R). This parameter treats a short fiber reinforced injection-molded composite as a laminate, in the layers of which the fibers are present in different amounts, in various orientations and in addition, in various aspect ratios and aspect ratio distributions. The relative change in the Fracture toughness can be predicted by the microstructural efficiency concept (M). Due to analogies between Static Fracture and fatigue crack propagation (FCP) results, this concept seems to work well when the dependence of FCP on microstructural details is considered.
Ove A Peters - One of the best experts on this subject based on the ideXlab platform.
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effect of cyclic fatigue on Static Fracture loads in protaper nickel titanium rotary instruments
2005Co-Authors: Cheryl J Ullmann, Ove A PetersAbstract:The aim of the present study was to evaluate Static Fracture loads of ProTaper Nickel-Titanium instruments that had been subjected to various degrees of cyclic fatigue. Torque and angle at failure of new instruments and instruments that had been stressed to 30, 60, or 90% of their cyclic fatigue rotations in a simulated canal (90 degrees and 5 mm radius) were tested according to ISO 3630-1. With unused ProTaper instruments, resistance to cyclic fatigue decreased with diameter increase and ranged from 158 to 450 rotations. Torque at failure ranged from 0.5 to 2.1 Ncm and showed a strong linear relationship to instrument diameter (r = 0.9) while angle at failure was weakly related to diameter (r = 0.46). Cyclic prestressing significantly reduced torsional resistance in finishing files, while shaping files were largely unaffected. In conclusion, build-up of tension within NiTi rotary instruments depends on instrument diameter. Clinically, larger instruments that have been subjected to some cyclic fatigue should be used with great care or discarded.
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effect of cyclic fatigue on Static Fracture loads in protaper nickel titanium rotary instruments
2005Co-Authors: Cheryl J Ullmann, Ove A PetersAbstract:Abstract The aim of the present study was to evaluate Static Fracture loads of ProTaper Nickel-Titanium instruments that had been subjected to various degrees of cyclic fatigue. Torque and angle at failure of new instruments and instruments that had been stressed to 30, 60, or 90% of their cyclic fatigue rotations in a simulated canal (90° and 5 mm radius) were tested according to ISO 3630-1. With unused ProTaper instruments, resistance to cyclic fatigue decreased with diameter increase and ranged from 158 to 450 rotations. Torque at failure ranged from 0.5 to 2.1 Ncm and showed a strong linear relationship to instrument diameter ( r 2 = 0.9) while angle at failure was weakly related to diameter ( r 2 = 0.46). Cyclic prestressing significantly reduced torsional resistance in finishing files, while shaping files were largely unaffected. In conclusion, build-up of tension within NiTi rotary instruments depends on instrument diameter. Clinically, larger instruments that have been subjected to some cyclic fatigue should be used with great care or discarded.
H Koerber - One of the best experts on this subject based on the ideXlab platform.
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Determination of the crack resistance curve for intralaminar fiber tensile failure mode in polymer composites under high rate loading
2018Co-Authors: Peter Kuhn, M. Ploeckl, J. Xavier, Giuseppe Catalanotti, H KoerberAbstract:This paper presents the determination of the crack resistance curve of the unidirectional carbon-epoxy composite material IM7-8552 for intralaminar fiber tensile failure under dynamic loading. The methodology, proposed by Catalanotti et al. (2014) for quasi-Static loading conditions, was enhanced to high rate loading in the order of about 60 s−1. Dynamic tests were performed using a split-Hopkinson tension bar, while quasi-Static reference tests were conducted on a standard electromechanical testing machine. Double-edge notched tension specimens of different sizes were tested to obtain the size effect law, which in combination with the concepts of the energy release rate is used to measure the entire crack resistance curve for the fiber tensile failure mode. Digital image correlation is applied to further verify the validity of the experiments performed at both Static and dynamic loading. The data reduction methodology applied in this paper is suitable for intralaminar fiber failure modes without significant delamination. Sufficient proof is given that quasi-Static Fracture mechanics theory can also be used for the data reduction of the dynamic tests. It is shown, that the intralaminar Fracture toughness for fiber tensile failure of UD IM7-8552 increases with increasing rate of loading.
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Fracture toughness and crack resistance curves for fiber compressive failure mode in polymer composites under high rate loading
2017Co-Authors: Peter Kuhn, J. Xavier, Pedro P. Camanho, Giuseppe Catalanotti, H KoerberAbstract:This work presents an experimental method to measure the compressive crack resistance curve of fiber-reinforced polymer composites when subjected to dynamic loading. The data reduction couples the concepts of energy release rate, size effect law and R-curve. Double-edge notched specimens of four different sizes are used. Both split-Hopkinson pressure bar and quasi-Static reference tests are performed. The full crack resistance curves at both investigated strain rate regimes are obtained on the basis of quasi-Static Fracture analysis theory. The results show that the steady state Fracture toughness of the fiber compressive failure mode of the unidirectional carbon-epoxy composite material IM7-8552 is 165.6 kJ/m2 and 101.6 kJ/m2 under dynamic and quasi-Static loading, respectively. Therefore the intralaminar Fracture toughness in compression is found to increase with increasing strain rate.
Arshad Munir - One of the best experts on this subject based on the ideXlab platform.
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quasi Static and impact Fracture behaviors of cfrps with nanoclay filled epoxy matrix
2011Co-Authors: Shafi Ullah Khan, Kosar Iqbal, Arshad MunirAbstract:The influence of nanoclay on the Fracture resistance and mechanical properties of epoxy-based nanocomposites and the corresponding continuous carbon fiber–epoxy matrix composites (CFRPs) has been studied. The incorporation of nanoclay into epoxy and CFRP enhances the impact and quasi-Static Fracture resistance, as well as the flexural strength and modulus of the composites. Microscopic examination based on the double-notch bending test identifies pertinent toughening mechanisms responsible for the enhanced toughness of clay nanocomposites, namely microcracking, crack pining, crack tip bifurcation and deflection, and microvoids along the clay galleries. Multi-layer delaminations are among the key toughening mechanisms identified for the clay–CFRP hybrid composites.
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mode i interlaminar Fracture behavior and mechanical properties of cfrps with nanoclay filled epoxy matrix
2007Co-Authors: Christopher Ky Leung, Naveed A Siddiqui, Arshad MunirAbstract:Abstract The mechanical properties and Fracture behavior of nanocomposites and carbon fiber composites (CFRPs) containing organoclay in the epoxy matrix have been investigated. Morphological studies using TEM and XRD revealed that the clay particles within the epoxy resin were intercalated or orderly exfoliated. The organoclay brought about a significant improvement in flexural modulus, especially in the first few wt% of loading, and the improvement of flexural modulus was at the expense of a reduction in flexural strength. The quasi-Static Fracture toughness increased, whereas the impact Fracture toughness dropped sharply with increasing the clay content. Flexural properties of CFRPs containing organoclay modified epoxy matrix generally followed the trend similar to the epoxy nanocomposite although the variation was much smaller for the CFRPs. Both the initiation and propagation values of mode I interlaminar Fracture toughness of CFRP composites increased with increasing clay concentration. In particular, the propagation Fracture toughness almost doubled with 7 wt% clay loading. A strong correlation was established between the Fracture toughness of organoclay-modified epoxy matrix and the CFRP composite interlaminar Fracture toughness.
Antonio Scarano - One of the best experts on this subject based on the ideXlab platform.
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in vitro interface changes of two vs three narrow diameter dental implants for screw retained bar under fatigue loading test
2019Co-Authors: Dental Suppleme, Felice Lorusso, F Mastrangelo, Francesco Inchingolo, C Mortellaro, Antonio ScaranoAbstract:The mechanical failure of a dental implant is clinically related to a prosthetic overload dissipated on the fixture/abutment complex. The aim of this investigation was to evaluate the Fracture strength of two vs three narrow-diameter dental implant configurations for screw-retained bars. Different configurations of screw-retained bars on two narrow-diameter dental implants (Group I) and screw-retained bars on three narrow-diameter dental implants (Group II) were tested under a Static Fracture loading. A total of 20 specimens, 10 for each group were evaluated. The Fracture loading point was significatively higher in Group I (p<0.05). The experimental groups reported high levels of Fracture strength under loading that encourages the clinical application of screw-retained bars supported by multiple narrow-diameter implants.
