Whisker Orientation Measurements in Injection Molded Si3N4-SiC Composites

1988 ◽  
Author(s):  
J. T. Neil ◽  
D. A. Norris
Keyword(s):  
Fracture Toughness ◽  
Composite Material ◽  
Silicon Nitride ◽  
Aspect Ratio ◽  
Injection Molding ◽  
Hot Isostatic Pressing ◽  
Sem Micrographs ◽  
Sic Whiskers ◽  
Injection Molded ◽  
Sic Composites

Hot pressed composites of Si3N4 containing 30% SiC whiskers have shown substantial improvements in strength and fracture toughness relative to monolithic silicon nitride. Injection molded samples made of this composite material distorted in a systematic manner during densification by hot isostatic pressing. Whisker orientation and aspect ratio measurements based on digitized SEM micrographs were used to evaluate microstructure with respect to injection molding direction. Results show definite orientation of whiskers during injection molding which can be related to the observed densification distortion.

Precipitate phases in an Al-SiC composite

1984 ◽  
Vol 42 ◽  
pp. 490-491
Author(s):  
S.R. Nutt ◽  
R.W. Carpenter
Keyword(s):  
Fracture Toughness ◽  
Composite Material ◽  
Alloy Powder ◽  
Heat Treating ◽  
Matrix Alloy ◽  
Al Alloy ◽  
Unreinforced Alloy ◽  
The Matrix ◽  
Sic Whiskers ◽  
Sic Composites

The modulus of many aluminum alloys can be greatly increased by the addition of small amounts of silicon carbide. The resulting composite material is also stronger than the unreinforced alloy, but exhibits poor fracture toughness. The reason for the low ductility of Al-SiC composites is unknown, although results presented here indicate that embrittling phases present in the matrix alloy may be partially responsible. The purpose of this work has been to study the distribution of precipitate phases in Al-SiC composites, focusing particular attention on interface regions. The material studied was fabricated by adding SiC whiskers to a 2124 Al alloy powder, consolidating, then heat treating to a T6 temper.

scholarly journals Fracture Toughness Improvement of Poly(lactic acid) Reinforced with Poly(ε-caprolactone) and Surface-Modified Silicon Carbide

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Jie Chen ◽  
Tian-Yi Zhang ◽  
Fan-Long Jin ◽  
Soo-Jin Park
Keyword(s):  
Fracture Toughness ◽  
Silicon Carbide ◽  
Lactic Acid ◽  
Poly Lactic Acid ◽  
External Energy ◽  
Solution Blending ◽  
Blending Method ◽  
Sic Whiskers ◽  
Sic Composites ◽  
Surface Modified

In this study, bio-based poly(lactic acid) (PLA)/polycaprolactone (PCL) blends and PLA/PCL/silicon carbide (SiC) composites were prepared using a solution blending method. The surface of the SiC whiskers was modified using a silane coupling agent. The effects of the PCL and SiC contents on the flexural properties, fracture toughness, morphology of PLA/PCL blends, and PLA/PCL/SiC composites were investigated using several techniques. Both the fracture toughness and flexural strength of PLA increased by the introduction of PCL and were further improved by the formation of SiC whiskers. Fracture surfaces were observed by scanning electron microscopy, which showed that the use of PCL as a reinforcing agent induces plastic deformation in the PLA/PCL blends. The SiC whiskers absorbed external energy because of their good interfacial adhesion with the PLA matrix and through SiC-PLA debonding in the PLA/PCL/SiC composites.

scholarly journals Peculiarities of Injection Molding Conducting Composites

2018 ◽  
Vol 248 ◽  
pp. 01006
Author(s):  
Yovial Mahyoedin ◽  
Jaafar Sahari ◽  
Andanastuti Mukhtar ◽  
Norhamidi Mohammad ◽  
Iqbal
Keyword(s):  
Composite Material ◽  
Carbon Black ◽  
Injection Molding ◽  
Test Procedure ◽  
Molded Parts ◽  
Twin Screw ◽  
Probe Test ◽  
Injection Molded ◽  
Conducting Composites

The investigations in this study focused on the characteristic of feedstock in an effort to understand the mechanism of injection molded in composite material. A composite, which has 75% wt. filler, consist of graphite (G), carbon black (CB) and polypropylene copolymer (PP). Twin-screw co-rotating extruder used for mixing materials. The conductivity of the molded parts measured using a four-point probe test procedure. The results showed that the injection molding conducting composites, which aggregated into larger clusters, tended to disperse unevenly into the PP, resulting in fewer particle-particle contacts and, consequently, a lower-conductivity composite in some part of the molded.

Preparation and Flame Ablation/Oxidation Behavior of ZrB2/SiC Ultra-High Temperature Ceramic Composites

2007 ◽  
Vol 351 ◽  
pp. 142-146 ◽  
Author(s):  
Chang An Wang ◽  
Hai Long Wang ◽  
Yong Huang ◽  
Dai Ning Fang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Thermal Ablation ◽  
Oxidation Behavior ◽  
Ceramic Composites ◽  
Argon Atmosphere ◽  
Good Resistance ◽  
Sic Ceramic ◽  
Sic Whiskers ◽  
Sic Composites

ZrB2/SiC ceramic composites reinforced by nano-SiC whiskers and SiC particles have been prepared by hot-pressing at 1950°C for 1hr under 20 MPa pressure in flow argon atmosphere. Effects of SiC addition on microstructure, mechanical properties and thermal ablation/oxidation behavior of ZrB2/SiC composites were investigated. The results showed that the addition of SiC effectively improved the densification of ZrB2/SiC composites and almost full dense ZrB2/SiC composites were obtained when the amount of SiC increased up to 20 vol%. Flexural strength and fracture toughness of the ZrB2/SiC composites were also enhanced; the maximum strength and toughness reached 600 MPa and 8.81 MPa·m1/2 at SiC additions of 20 vol % and 30 vol%, respectively. The composites possessed good resistance to flame ablation and could keep the whole shape without distinct peeling or cracking after flame ablation by oxyacetylene flame for 3 mins. The more SiC added, the better resistance to flame ablation the composites displayed.

Mechanical properties of hot isostatically pressed Si3N4 and Si3N4/SiC composites

1993 ◽  
Vol 8 (3) ◽  
pp. 626-634 ◽  
Author(s):  
O. Unal ◽  
J.J. Petrovic ◽  
T.E. Mitchell
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Hardness ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Sic Whiskers ◽  
Sic Composites ◽  
Increasing Temperature

The mechanical properties of hot isostatically pressed monolithic Si3N4 and Si3N4−20 vol. % SiC composites have been studied by microindentation at temperatures up to 1400 °C. Indentation crack patterns and microstructures have been examined by optical microscopy, scanning electron microscopy, and transmission electron microscopy. It is shown that dense Si3N4 base materials can be synthesized by HIPing without densification aids. Both the monolithic Si3N4 and the Si3N4/SiC composites exhibit high hardness values which gradually decrease with increasing temperature. Both types of material show low fracture toughness values apparently because of strong interfacial bonding. On the other hand, the fracture toughness of the composite is about 40% higher than that of the monolithic material, due to the presence of the 20 vol. % SiC whiskers. A crack deflection/debonding mechanism is likely to be responsible for the higher toughness observed in the composite. High resolution electron microscopy shows that the grain boundaries in both samples contain a thin SiO2 layer.

Fracture Toughness of Si3N4 Based Ceramics with Rare-Earth Oxide Sintering Additives

2009 ◽  
Vol 409 ◽  
pp. 377-381 ◽  
Author(s):  
Peter Tatarko ◽  
Štefánia Lojanová ◽  
Ján Dusza ◽  
Pavol Šajgalík
Keyword(s):  
Fracture Toughness ◽  
Rare Earth ◽  
Silicon Nitride ◽  
Aspect Ratio ◽  
Rare Earth Oxide ◽  
Rare Earth Oxides ◽  
Crack Deflection ◽  
Indentation Fracture ◽  
Toughening Mechanisms ◽  
Sintering Additives

Fracture toughness of hot-pressed silicon nitride and Si3N4+SiC nanocomposites prepared with different rare-earth oxides (La2O3, Sm2O3, Y2O3, Yb2O3, Lu2O3) sintering additives have been investigated by Chevron Notched Beam, Indentation Strength and Indentation Fracture techniques. The fracture toughness values of composites were lower due to the finer microstructures and the lack of toughening mechanisms. In the Si3N4 with higher aspect ratio (Lu or Yb additives) crack deflection occurred more frequently compared to the Si3N4 doped with La or Y, which was responsible for the higher fracture toughness.

scholarly journals Injection-Molded and Isopressed α-SiC Components for Stationary Gas Turbine Applications

1995 ◽  
Author(s):  
R. W. Ohnsorg ◽  
S. K. Lau ◽  
M. O. Ten Eyck ◽  
D. A. White
Keyword(s):  
Tensile Strength ◽  
Injection Molding ◽  
Nondestructive Evaluation ◽  
Gas Turbine ◽  
Material Properties ◽  
Hot Isostatic Pressing ◽  
Development Program ◽  
Tensile Specimen ◽  
Injection Molded ◽  
Fast Fracture

Sintered α-SiC (HEXOLOY®1 SA) injection-molded buttonhead tensile specimens and isostatically pressed combustor tiles were developed and fabricated by Carborundum for the DOE/Solar Ceramic Stationary Gas Turbine (CSGT) development program. Tooling designs, processing details, material properties, and nondestructive evaluation (NDE) procedures are discussed. Post-sinter hot isostatic pressing (HIPing), which improves density, strength and uniformity, was done on all components. Both injection-molded and isopressed flexure bars produced strengths in excess of 621 MPa (90 ksi), while the fast-fracture tensile strength of injection-molded HEXOLOY® SA SiC was 453 MPa (66 ksi). The injection-molding and isopressing process changes leading to HEXOLOY® SA SiC strength increases are discussed, a recent properties summary on delivered test specimens is given, the buttonhead tensile specimen and combustor tile processing issues are described, and proposed process modifications to enhance fabrication economics are suggested.

Fracture Toughness of Discontinuous Long Glass Fiber Reinforced Polypropylene: An Approach Based on a Numerical Prediction of Fiber Orientation in Injection Molding

2005 ◽  
Vol 13 (2) ◽  
pp. 121-130 ◽  
Author(s):  
V. Rizov ◽  
T. Harmia ◽  
A. Reinhardt ◽  
K. Friedrich
Keyword(s):  
Fracture Toughness ◽  
Injection Molding ◽  
Glass Fiber ◽  
Fiber Orientation ◽  
Numerical Prediction ◽  
Fiber Reinforced ◽  
Local Fracture ◽  
Glass Fiber Reinforced ◽  
Long Glass Fiber ◽  
Injection Molded

The fracture toughness of discontinuous long glass fiber reinforced injection-molded polypropylene has been characterized by using the microstructural efficiency concept in combination with a numerical prediction of the fiber orientation during injection molding. The latter was performed by using the SIGMASOFT commercial software. In a three-dimensional numerical scheme, input data such as fiber volume fractions, shear viscosity and mean fiber aspect ratio have been used in order to perform the mold filling analysis. The resulted local fiber orientation parameters for injection molded square plates of long glass fiber reinforced polypropylene allowed to calculate the local fracture toughness with microstructural efficiency concept. The latter were compared with the experimental toughness values obtained by the use of compact tension test specimens. The good correlation between the calculated fracture toughness data and the measured ones shows that a fiber orientation prediction by the SIGMASOFT finite element computer code can be used in combination with the microstructural efficiency concept for the determination of local fracture toughness values in injection molded long glass fiber reinforced thermoplastics. The combined approach opens good opportunities for optimization of a thermoplastic workpiece in its design with respect to local fracture resistance. This will enable the material performance levels to be significantly extended, with consequent increases in engineering applicability.

scholarly journals Fabrication of Turbine Components and Properties of Sintered Silicon Nitride

1982 ◽  
Author(s):  
J. T. Neil ◽  
K. W. French ◽  
C. L. Quackenbush ◽  
J. T. Smith
Keyword(s):  
Silicon Nitride ◽  
Injection Molding ◽  
Turbine Blades ◽  
Status Report ◽  
Injection Molding Process ◽  
Molding Process ◽  
Radial Turbine ◽  
Structural Applications ◽  
Injection Molded ◽  
Sintered Silicon

This paper presents a status report on the injection molding of sinterable silicon nitride at GTE Laboratories. The effort involves fabrication of single axial turbine blades and monolithic radial turbine rotors. The injection molding process is reviewed and the fabrication of the turbine components discussed. Oxidation resistance and strength results of current injection molded sintered silicon nitride as well as dimensional checks on sintered turbine blades demonstrate that this material is a viable candidate for high temperature structural applications.

TEM Studies of Grain Boundary Films in Si3N4 Ceramics

1991 ◽  
Vol 49 ◽  
pp. 930-931
Author(s):  
H.-J. Kleebe ◽  
J.S. Vetrano ◽  
J. Bruley ◽  
M. Rühle
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Silicon Nitride ◽  
Hot Isostatic Pressing ◽  
Amorphous Film ◽  
Liquid Phase Sintering ◽  
Second Phase ◽  
High Temperature Mechanical Properties ◽  
Triple Points ◽  
Boundary Films

It is expected that silicon nitride based ceramics will be used as high-temperature structural components. Though much progress has been made in both processing techniques and microstructural control, the mechanical properties required have not yet been achieved. It is thought that the high-temperature mechanical properties of Si3N4 are limited largely by the secondary glassy phases present at triple points. These are due to various oxide additives used to promote liquid-phase sintering. Therefore, many attempts have been performed to crystallize these second phase glassy pockets in order to improve high temperature properties. In addition to the glassy or crystallized second phases at triple points a thin amorphous film exists at two-grain junctions. This thin film is found even in silicon nitride formed by hot isostatic pressing (HIPing) without additives. It has been proposed by Clarke that an amorphous film can exist at two-grain junctions with an equilibrium thickness.

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