scholarly journals Structure-Properties Relations for Polyamide 6, Part 2: Influence of Processing Conditions during Injection Moulding on Deformation and Failure Kinetics

Polymers ◽  
2018 ◽  
Vol 10 (7) ◽  
pp. 779 ◽  
Author(s):  
Emanuele Parodi ◽  
Gerrit Peters ◽  
Leon Govaert
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Mold Temperature ◽  
Polyamide 6 ◽  
Testing Temperature ◽  
Full Description ◽  
Time To Failure ◽  
Processing Conditions ◽  
Creep Tests ◽  
Deformation And Failure

The effect of processing conditions during injection on the structure formation and mechanical properties of injection molded polyamide 6 samples was investigated in detail. A large effect of the mold temperature on the crystallographic properties was observed. Also the the effect of pressure and shear flow was taken in to consideration and analysed. The yield and failure kinetics, including time-to-failure, were studied by performing tensile and creep tests at several test temperatures and relative humidities. As far as mechanical properties are concerned, a strong influence of temperature and relative humidity on the yield stress and time-to-failure was found. A semi-empirical model, able to describe yield and failure kinetics, was applied to the experimental results and related to the crystalline phase present in the sample. In agreement with findings in the literature it is observed that for high mold temperatures the sample morphology is more stable with respect to humidity and temperature than in case of low mold temperatures and this effects could be successfully captured by the model. The samples molded at low temperatures showed, during mechanical testing, a strong evolution of the crystallographic properties when exposed to high testing temperature and high relative humidity, i.e., an increase of crystallinity or a crystal phase transition. This makes a full description of the mechanical behavior rather complicated.

scholarly journals Lifetime assessment of high-density polyethylene–silica nanocomposites

2019 ◽  
Vol 9 ◽  
pp. 184798041984998 ◽  
Author(s):  
A Dorigato ◽  
LE Govaert ◽  
A Pegoretti
Keyword(s):  
Fumed Silica ◽  
High Density Polyethylene ◽  
Tensile Tests ◽  
Testing Temperature ◽  
High Density ◽  
Time To Failure ◽  
Creep Tests ◽  
Polyethylene Matrix ◽  
Significant Drop ◽  
Fumed Silica Nanoparticles

In this work, the effect of fumed silica on the long-term resistance of high-density polyethylene was investigated. Different amounts of functionalized fumed silica nanoparticles were dispersed in a high-density polyethylene matrix by melt compounding, and compression molded specimens were tested under tensile mode in the quasi-static ramp and creep conditions. In particular, tensile tests at different speeds and temperatures and the subsequent application of the modified Ree–Eyring model allowed the determination of an analytical expression correlating the strain rate with the yield stress and the testing temperature. It was demonstrated that the introduction of fumed silica led to a significant drop in the deformation rate, especially at elevated filler amounts. Creep tests showed that the nanofiller addition led to a progressive reduction of the critical deformation values. The application of this engineering approach evidenced how nanosilica introduction led to a systematic increase of the time-to-failure values, and good accordance between theoretical prediction and experimental measurements was found.

Processing Effects on Formation of Microvoids and Hydraulic Fluid Absorption of Quartz/BMI Laminates

2015 ◽  
Author(s):  
Keith R. Hurdelbrink ◽  
Jacob P. Anderson ◽  
Zahed Siddique ◽  
M. Cengiz Altan
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Fiber Volume Fraction ◽  
Volume Fraction ◽  
Void Content ◽  
Hydraulic Fluid ◽  
Processing Conditions ◽  
Fluid Absorption ◽  
Fiber Volume ◽  
Fluid Content

Bismaleimide (BMI) resin with Quartz (AQ581) fiber reinforcement is desirable for systems requiring a high glass transition temperature, low dielectric properties, and high laminate mechanical properties. These properties make quartz/BMI an ideal composite material for complex aerospace structures, and are currently being used in various aircraft engine cowlings and radomes. In addition to moisture absorption, quartz/BMI composite laminates are often exposed to different types of hydraulic fluid contaminants, which may lead to anomalous absorption behavior over the service life of the composite structure. Variations in laminate processing conditions, such as prepreg preconditioning and fabrication cure pressure, can have a significant effect on microstructural features of fiber-reinforced composites. Microstructural features, such as fiber volume fraction and void content, can influence mechanical properties and long term absorption of moisture or other liquid contaminants. In this paper, the process-induced microstructure and hydraulic fluid absorption behavior of quartz/BMI laminates are presented. The laminates are fabricated from preconditioned prepregs and cured at different pressures to generate different levels of microvoids, while keeping the fiber volume fraction constant. Location, size and morphology of microvoids are investigated via SEM images obtained from laminates cured at different processing conditions. Composite samples were prepared and fully-immersed in hydraulic fluid at room temperature, and were not subjected to any prior degradation. The laminate samples immersed in hydraulic fluid exhibited clear non-Fickian absorption behavior, which was successfully predicted by the one-dimensional Hindered Diffusion Model (HDM). The degree of non-Fickian absorption behavior, or hindrance coefficient (μ), ranged from 0.30 to 0.72. Model prediction indicates that as the fabrication pressure increased, the maximum fluid content (M∞) decreased considerably. Additionally, a reduction in maximum fluid content was observed when lower relative humidity environments were used for prepreg preconditioning. A discernable difference was not observed in the absorption dynamics when the prepregs were preconditioned at greater than 70% relative humidity.

Creep and Mechanical Properties of a Commercial Aluminum Alloy Processed by ECAP

2006 ◽  
Vol 503-504 ◽  
pp. 77-82 ◽  
Author(s):  
Cheng Xu ◽  
Terence G. Langdon
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Strain Rate ◽  
Testing Temperature ◽  
Cast Aluminum Alloy ◽  
Cast Aluminum ◽  
Creep Tests ◽  
Double Shear ◽  
Angular Pressing ◽  
Ultrafine Grained

A commercial spray-cast aluminum alloy, having a composition of Al-11.5% Zn-2.5% Mg-0.9% Cu-0.2% Zr, was processed by equal-channel angular pressing (ECAP) to give an ultrafine-grained microstructure with a grain size of ~0.3 μm and a fracturing of the rod-shaped MgZn2 precipitates. The mechanical properties of the alloy were investigated using microhardness testing at ambient temperature and tensile testing at a temperature of 673 K. In addition, creep tests were conducted using a double-shear testing facility at temperatures from 473 to 673 K. The results show the microhardness decreases with increasing numbers of passes in ECAP and high strain rate superplasticity is achieved after processing by ECAP at 473 K for 6 or 8 passes. A maximum elongation of >1000% was recorded at a strain rate of 10-2 s-1 when testing at 673 K. The creep tests show the creep rates are faster in the as-pressed material than in the as-received material when testing at the same applied stress and testing temperature.

scholarly journals Extrusion and Injection Molding of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx): Influence of Processing Conditions on Mechanical Properties and Microstructure

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4012
Author(s):  
Chris Vanheusden ◽  
Pieter Samyn ◽  
Bart Goderis ◽  
Mouna Hamid ◽  
Naveen Reddy ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mold Temperature ◽  
Melt Processing ◽  
Polymer Chains ◽  
Processing Temperature ◽  
Processing Conditions ◽  
Homogeneous Microstructure ◽  
Optimal Processing ◽  
Flexible Packaging ◽  
Factorial Design Of Experiments

Biobased and biodegradable polyhydroxyalkanoates (PHAs) have great potential as sustainable packaging materials. However, improvements in their processing and mechanical properties are necessary. In this work, the influence of melt processing conditions on the mechanical properties and microstructure of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) is examined using a full factorial design of experiments (DoE) approach. We have found that strict control over processing temperature, mold temperature, screw speed, and cooling time leads to highly increased elongation at break values, mainly under influence of higher mold temperatures at 80 °C. Increased elongation of the moldings is attributed to relaxation and decreased orientation of the polymer chains together with a homogeneous microstructure at slower cooling rates. Based on the statistically substantiated models to determine the optimal processing conditions and their effects on microstructure variation and mechanical properties of PHBHHx samples, we conclude that optimizing the processing of this biopolymer can improve the applicability of the material and extend its scope in the realm of flexible packaging applications.

Surface Modification and its Influence on the Microstructure and Creep Resistance of Nickel Based Superalloy René 77 / Modyfikacja Powierzchniowa Oraz Jej Wpływ Na Mikrostrukture I Wytrzymałosc Na Pełzanie Odlewów Z Nadstopu Niklu Ren´E 77

2013 ◽  
Vol 58 (1) ◽  
pp. 95-98 ◽  
Author(s):  
M. Zielinska ◽  
J. Sieniawski
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Surface Modification ◽  
Turbine Blades ◽  
Processing Parameters ◽  
Grain Structure ◽  
Creep Tests ◽  
Cobalt Aluminate ◽  
Nickel Based Superalloy ◽  
Average Grain Size

Superalloy René 77 is very wide used for turbine blades, turbine disks of aircraft engines which work up to 1050°C. These elements are generally produced by the investment casting method. Turbine blades produced by conventional precision casting methods have coarse and inhomogeneous grain structure. Such a material often does not fulfil basic requirements, which concern mechanical properties for the stuff used in aeronautical engineering. The incorporation of controlled grain size improved mechanical properties. This control of grain size in the casting operation was accomplished by the control of processing parameters such as casting temperature, mould preheating temperature, and the use of grain nucleates in the face of the mould. For nickel and cobalt based superalloys, it was found that cobalt aluminate (CoAl2O4) has the best nucleating effect. The objective of this work was to determine the influence of the inoculant’s content (cobalt aluminate) in the surface layer of the ceramic mould on the microstructure and mechanical properties at high temperature of nickel based superalloy René 77. For this purpose, the ceramic moulds were made with different concentration of cobalt aluminate in the primary slurry was from 0 to 10% mass. in zirconium flour. Stepped and cylindrical samples were casted for microstructure and mechanical examinations. The average grain size of the matrix ( phase), was determined on the stepped samples. The influence of surface modification on the grain size of up to section thickness was considered. The microstructure investigations with the use of light microscopy and scanning electron microscopy (SEM) enable to examine the influence of the surface modification on the morphology of ’ phase and carbides precipitations. Verification of the influence of CoAl2O4 on the mechanical properties of castings were investigated on the basis of results obtained form creep tests.

scholarly journals Evolution of the viscoelastic properties of painting stratigraphies: a moisture weathering and nanoindentation approach

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Mathilde Tiennot ◽  
Davide Iannuzzi ◽  
Erma Hermens
Keyword(s):  
Mechanical Properties ◽  
Relative Humidity ◽  
Cultural Heritage ◽  
Mechanical Behaviour ◽  
Viscoelastic Properties ◽  
Viscoelastic Behaviour ◽  
Storage And Loss Moduli ◽  
Heritage Studies ◽  
Paint Films ◽  
The Impact

AbstractIn this investigation on the mechanical behaviour of paint films, we use a new ferrule-top nanoindentation protocol developed for cultural heritage studies to examine the impact of repeated relative humidity variations on the viscoelastic behaviour of paint films and their mechanical properties in different paint stratigraphies through the changes in their storage and loss moduli. We show that the moisture weathering impact on the micromechanics varies for each of these pigment-oil systems. Data from the nanoindentation protocol provide new insights into the evolution of the viscoelastic properties dsue to the impact of moisture weathering on paint films.

scholarly journals Influence of Different Annealing Atmospheres on the Mechanical Properties of Freestanding MCrAlY Bond Coats Investigated by Micro-Tensile Creep Tests

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 692 ◽  
Author(s):  
Sven Giese ◽  
Steffen Neumeier ◽  
Jan Bergholz ◽  
Dmitry Naumenko ◽  
Willem J. Quadakkers ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Creep Strength ◽  
Bond Coat ◽  
Oxide Dispersion Strengthened ◽  
Tensile Creep ◽  
Creep Tests ◽  
Bond Coats ◽  
Nial Phase ◽  
Lower Strain ◽  
Plasma Sprayed

The mechanical properties of low-pressure plasma sprayed (LPPS) MCrAlY (M = Ni, Co) bond coats, Amdry 386, Amdry 9954 and oxide dispersion strengthened (ODS) Amdry 9954 (named Amdry 9954 + ODS) were investigated after annealing in three atmospheres: Ar–O2, Ar–H2O, and Ar–H2–H2O. Freestanding bond coats were investigated to avoid any influence from the substrate. Miniaturized cylindrical tensile specimens were produced by a special grinding process and then tested in a thermomechanical analyzer (TMA) within a temperature range of 900–950 °C. Grain size and phase fraction of all bond coats were investigated by EBSD before testing and no difference in microstructure was revealed due to annealing in various atmospheres. The influence of annealing in different atmospheres on the creep strength was not very pronounced for the Co-based bond coats Amdry 9954 and Amdry 9954 + ODS in the tested conditions. The ODS bond coats revealed significantly higher creep strength but a lower strain to failure than the ODS-free Amdry 9954. The Ni-based bond coat Amdry 386 showed higher creep strength than Amdry 9954 due to the higher fraction of the β-NiAl phase. Additionally, its creep properties at 900 °C were much more affected by annealing in different atmospheres. The bond coat Amdry 386 annealed in an Ar–H2O atmosphere showed a significantly lower creep rate than the bond coat annealed in Ar–O2 and Ar–H2–H2O atmospheres.

The effects of Clay on fire performance and thermal mechanical properties of woven glass fibre reinforced polyamide 6 nanocomposites

2010 ◽  
Vol 70 (14) ◽  
pp. 2063-2067 ◽  
Author(s):  
Shirley Zhiqi Shen ◽  
Stuart Bateman ◽  
Patrick McMahon ◽  
Mel Dell’Olio ◽  
Januar Gotama ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Glass Fibre ◽  
Polyamide 6 ◽  
Fire Performance ◽  
Thermal Mechanical Properties ◽  
Glass Fibre Reinforced
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