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1.
Mechanical properties of chopped carbon fiber (CF) reinforced PC/ABS composites were investigated. Tensile strength and elastic
modulus of the composites were enhanced with increasing CF contents. On the contrary, impact strength of the composite was
decreased with increasing CF fraction. Film insert molding was introduced in order to improve impact strength. Film insert
molded composite specimens have higher impact strength than conventional injection molded composite specimens because inserted
film acted as a cushion to absorb the impact energy. Large warpage which was observed after molding and known as a disadvantage
of the film insert molded part can be prevented by controlling the amount of filled CFs. Therefore, fiber reinforcement and
film insert molding can be applied simultaneously to reduce warpage of the film insert molded part and enhance impact strength
of the CF reinforced composite. 相似文献
2.
Residual stresses were predicted by a flow analysis in the mold cavity and residual stress distribution in the injection molded
product was measured. Flow field was analyzed by the hybrid FEM/FDM method, using the Hele Shaw approximation. The Modified
Cross model was used to determine the dependence of the viscosity on the temperature and the shear rate. The specific volume
of the polymer melt which varies with the pressure and temperature fields was calculated by the Tait’s state equation. Flow
analysis results such as pressure, temperature, and the location of the liquid-solid interface were used as the input of the
stress analysis. In order to calculate more accurate gap-wise temperature field, a coordinate transformation technique was
used. The residual stress distribution in the gap-wise direction was predicted in two cases, the free quenching and the constrained
quenching, under the assumption that the shrinkage of the injection molded product occurs within the mold cavity and that
the solid polymer is elastic. Effects of the initial flow rate, packing pressure, and mold temperature on the residual stress
distribution was discussed. Experimental results were also obtained by the layer removal method for molded polypropylene. 相似文献
3.
A vertebral cage is a hollow medical device which is used in spine surgery. By implanting the cage into the spine column,
it is possible to restore disc and relieve pressure on the nerve roots. Most cages have been made of titanium alloys but they
detract the biocompatibility. Currently PEEK (polyether ether ketone) is applied to various implants because it has good properties
like heat resistance, chemical resistance, strength, and especially biocompatibility. A new shape of vertebral cage is designed
and injection molding of PEEK is considered for production. Before injection molding of the cage, it is needed to evaluate
process conditions and properties of the final product. Variables affecting the shrinkage of the cage are considered, e.g.,
injection time, packing pressure, mold temperature, and melt temperature. By using the numerical simulation program, MOLDFLOW,
several cases are studied. Data files obtained by MOLDFLOW analysis are used for stress analysis with ABAQUS, and shrinkage
and residual stress fields are predicted. With these results, optimum process conditions are determined. 相似文献
4.
Injection molding is one of the most popular manufacturing methods for the cost-effective mass production of the plastic parts. Filling analysis of the molten polymer provides useful information to investigate the process conditions to ensure successful replication. To validate appropriate gate location for a NEEDLE COVER, flow fronts and flow stresses for four different gating options and three different design options are analyzed and compared to the field results. Based on the results, the optimum gate location for the minimum flow stresses and uniform fill patterns appears to be at gate 3. Thus it also provides minimum possibility of part warpage throughout PORT HOUSING and NEEDLE HOUSING. The results of analysis on the increased wall thickness, lower melt temperature, and longer injection time indicated that higher melt temperatures were recommended to achieve successful molding. Injecting the polymer at a longer time (1.2 second) leads to a significant increase in flow stresses throughout the part and the increase of wall thickness achieve successful replication of the parts. 相似文献
5.
Injection molding has been widely used in the manufacturing of various polymer products, including housewares, home appliances, and automotive parts. A disposable medical device based on polymeric material at a low cost is another important area for injection molding. The numerical analysis was performed to predict the potential problem, often occurring during the manufacturing process of the medical device. Computer-aided engineering model was developed using industry-standard molding software, MOLDFLOW®. The flow pattern of the molten polymer was investigated in the replication of butterfly shaped Catheter Support for various catheterization. The flow pattern and temperature distribution of the molded part were investigated through a series of analysis. The results of analysis with original design predicted non-uniform polymer flow with a poor weld line, unbalanced cavity filling, and uneven temperature distribution of the part. An appropriate gate location to achieve uniform flow pattern for mold filling was determined on the base of the predicted results and experience, considering the performance of the product and limitation of the production. 相似文献
6.
This study examines multiple quality optimization of the injection molding for Polyether Ether Ketone (PEEK). It also looks
into the dimensional deviation and strength of screws that are reduced and improved for the molding quality, respectively.
This study applies the Taguchi method to cut down on the number of experiments and combines grey relational analysis to determine
the optimal processing parameters for multiple quality characteristics. The quality characteristics of this experiment are
the screws’ outer diameter, tensile strength and twisting strength. First, one should determine the processing parameters
that may affect the injection molding with the L18(21×37) orthogonal, including mold temperature, pre-plasticity amount, injection pressure, injection speed, screw speed, packing
pressure, packing time and cooling time. Then, the grey relational analysis, whose response table and response graph indicate
the optimum processing parameters for multiple quality characteristics, is applied to resolve this drawback. The Taguchi method
only takes a single quality characteristic into consideration. Finally, a processing parameter prediction system is established
by using the back-propagation neural network. The percentage errors all fall within 2%, between the predicted values and the
target values. This reveals that the prediction system established in this study produces excellent results. 相似文献
7.
Optimized palm press fiber composites of poly(?-caprolactone)/poly(lactic acid) were produced and their mechanical and thermal properties were studied. The composites were melt blended using twin screw extruder and test specimens were produced by injection molding. The composites mechanical and thermal performances were tested using standard methods. The incorporation of dicumyl peroxide as compatibilizer significantly increased the tensile strength, flexural modulus and impact strength of the composites as compared to the uncompatibilized composites. Crystallization temperature of the composites initially increased after which it dropped as fiber load increased. The composites melting point and percentage crystallinity slightly decreased as fiber load increased. 相似文献
8.
This paper is aiming to develop high shrinkable differential shrinkage and mixed fibre nylon composite yarns by applying the
high shrinkable polyester manufacturing technology. The wet and dry thermal shrinkages and mechanical properties of developed
nylon composite yarns are measured and discussed with processing factors in the spinning and texturing processes. And the
effects of the processing factors on the physical properties of high shrinkable nylon composite yarns are investigated. For
this purpose, twenty seven nylon 30d/12f SDY were prepared with variation of spinning temperature, 2nd godet roller temperature
and draw ratio on the spinning machine. The optimum spinning condition which showed maximum wet thermal shrinkage and stress
was determined and high shrinkable nylon 30d/12f SDY spun under this optimum condition used as a core and three kinds of regular
nylon filaments used as sheath were processed on the texturing machine with variation of 1st and 2nd heater temperatures.
The optimum texturing process condition was decided through analysis of dry thermal shrinkage of these core and sheath nylon
filaments. Finally, high shrinkable differential shrinkage and mixed fibre nylon composite yarns were made under the optimum
texturing condition on the texturing machine, its wet thermal shrinkage was 13.8 %, which was much more higher than that of
regular nylon composite yarns. The differential shrinkage effect of the developed nylon composite yarns was found in the yarn
surface and cross section profiles by microscope and SEM. 相似文献
9.
Ying Xia Ran Liu Xiaoxiao Lyu Hui Zhang Qian Wang Jing Guo Yumei Gong 《Fibers and Polymers》2014,15(10):2181-2185
In order to improve the thermostability and fire resistance of kenaf, kenaf was treated with halogen-free flame retardant triethyl phosphate (TEP) adopting dipping principle. Adding flame retardant kenaf (fbk) to high impact polystyrene (HIPS) resin, fbk/HIPS composites were prepared by extrusion molding and injection molding. The differences of untreated kenaf and treated kenaf on structure, thermal behavior, combustion, mechanical properties of HIPS were contrasted and analyzed. The results showed that kenaf treated with TEP had superior thermal stability at high temperature and produced significantly reinforcing effect on HIPS resin. 相似文献
10.
Khadija M. Zadeh I. M. Inuwa Reza Arjmandi Azman Hassan M. Almaadeed Zurina Mohamad P. Noorunnisa Khanam 《Fibers and Polymers》2017,18(7):1330-1335
This work investigated the effects of date palm leaf fiber (DPLF) content on the thermal and tensile properties; and morphology of compatibilized polyolefin ternary blend. Recycled polyolefin ternary blend consisting of low density polyethylene (RLDPE), high density polyethylene (RHDPE) and polypropylene (RPP) were fabricated at different parts per hundred resin (phr) of DPLF. Maleic anhydride grafted polyethylene (MAPE) was used as compatibilizer to enhance the adhesion between filler and polymer matrix. The composites were prepared using melt extrusion and tests samples were produced via injection molding process. Thermal conductivity results showed that as much as 11 % reduction in thermal conductivity was achieved with the incorporation of 30 phr DPLF. Highest tensile strength was observed with the incorporation of 10 phr DPLF. The elongation at break was reduced with the addition of DPLF due to impediment of chain mobility by the fillers. Initial degradation temperature increased with the addition of DPLF. Hence, it is concluded that DPLF can be used to develop green and thermally insulating composites. It is hoped that the present results will stimulate further studies on the thermally insulative materials based on natural fibers reinforced polymer composites for applications in the building industries. 相似文献
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Injection molding is a flexible production method for manufacturing polymer products, but introduces residual stresses. This study employs the incremental hole-drilling method to measure the residual stresses in injection molded parts. To compare the results, the layer-removal method is utilized for measurement of residual stresses. A commercial software, Moldflow, is used for prediction of residual stresses in molded plastic parts. Results obtained by experiments and Moldflow analysis are compared. The incremental hole-drilling method is applicable to determination of the residual stresses in complex geometries and can be used as an adoptable technique for measurement of the residual stress in polymeric materials. 相似文献
14.
15.
Choon Gil Lee 《Fibers and Polymers》2006,7(1):51-56
Power net fabric is one of the highly extensible two-way fabrics. Power net structure shows special characteristics in the
wearing of final functional clothes. This research evaluated effects of treatment temperature on proportional extensibility
and shrinkage ratio of spandex at a given wale length. As treatment temperature increased, extensibility increased proportionally
to the standard length of the sample and the shrinkage ratio in the direction of course and wale increased. The pulling-out
length increased proportionally to the standard length of the sample. However it was affected by the effect of treatment time
and temperature due to the thermal properties of spandex filament yarn. 相似文献
16.
The present paper reports the impact of thermal treatment on the characteristics of core-sheath type hybrid technical yarns.
The core-sheath type hybrid yarns are prepared using DREF-III technology. Polyester and glass multifilaments are used as core
components whereas the cotton and polyester staple fibers are the sheath components wrapped around the core filament with
different proportions to form a hybrid structure. The thermal treatment is carried out both in dry and in wet state under
relaxed condition and the thermal shrinkage, sheath-slipping resistance and tensile and bending properties of hybrid yarns
have been studied. Thermal treatment markedly increases the thermal shrinkage and sheath-slipping resistance of hybrid yarns
with polyester multifilament in core, but insignificant effect for yarns with glass multifilament in core. Breaking elongation
of hybrid yarns with polyester multifilament in core increases with treatment temperature. The hybrid yarns with glass multifilament
in core are least affected by thermal treatment. 相似文献
17.
A comparison of poly(trimethylene terephthalate)(PTT) and poly(ethlene terephthalate)(PET) fibers spun at various take-up
speeds was presented. Fiber characterization included tensile and thermal properties, optical birefringence, density, sonic
modulus, boil-off shrinkage, and wide-angle X-ray diffraction. The phenomenon of stress-induced crystallization was inferred
from the X-ray diffraction diagrams for fibers spun with take-up speeds over 4000 m/min. The tenacity and elongation of PTT
and PET fiber showed typical results, but the initial modulus of PTT fiber was nearly unchanged over the entire take-up speed
range (2000–7000 m/min), whereas that of PET, as expected, increased monotonically with increasing take-up speed. This divergent
behavior could be explained by the different molecular deformations in the c-axis as determined from X-ray diffraction patterns.
The fiber crystallinity, density, and heat of fusion of both polymers increased with take-up speed. The boil-off shrinkage
decreased with increasing take-up speed. The optical birefringence of the two fiber types showed a maximum level at a take-up
speed of ca. 5000 m/min. The melting temperature behavior of PTT fiber was different from that of PET fibers. It was found
that PTT is less sensitive to stress induced changes at high spinning speeds than is PET. 相似文献
18.
I.?M.?Inuwa Reza?Arjmandi Akos?Noel?Ibrahim M.?K.?Mohamad?Haafiz S.?L.?Wong Khaliq?Majeed Azman?Hassan
The effects of graphene nanoplatelets (GNP) and multiwall carbon nanotube (MWCNT) hybrid nanofillers on the mechanical and thermal properties of reinforced polyethylene terephthalate (PET) have been investigated. The nanocomposites were melt blended using the counter rotating twin screw extruder followed by injection molding. Their morphology, mechanical and thermal properties were characterized. Combination of the two nanofillers in composites formulation supplemented each other which resulted in the overall improvement in adhesion between fillers and matrix. The mechanical properties and thermal stability of the hybrid nanocomposites (PET/GNP1.5/MWCNT1.5) were significantly improved compared to PET/GNP3 and PET/MWCNT3 single filer nanocomposites. However, it was observed that GNP was better in improving the mechanical properties but MWCNT resulted in higher thermal stability of Nanocomposite. The transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM) revealed uniform dispersion of the hybrid fillers in PET/GNP1.5/MWCNT1.5 nanocomposites while agglomeration was observed at higher filler content. The MWCNT prevented the phenomenal stacking of the GNPs by forming a bridge between adjacent GNP planes resulting in higher dispersion of fillers. This complimentary geometrical structure is responsible for the significant improvement in the thermal stability and mechanical properties of the hybrid nanocomposites. 相似文献
19.
Although thermally conductive composites that can efficiently dissipate the heat generated from electronic devices are in high demand, most neat polymers used as matrix materials are problematic because they have poor thermal conductivities. The low thermal conductivity of polymeric materials is caused by structural defects; therefore, it can be improved by increasing the orientational regularity of the polymer chains. Here, main-chain liquid crystalline polymers (LCPs) were designed and synthesized to investigate the effects of liquid crystallinity-induced structural regularity on the thermal conductivity of the polymers. In addition, an in-situ polymerization method was devised for commercial applicability, and the thermal conductivity of the obtained polymer was compared to that of a conventionally polymerized polymer having the same structure. The designed polymers exhibited thermotropic liquid crystalline characteristics, and the polymer with longer spacers between the rigid segments showed relatively higher thermal conductivity exceeding 0.5 W·m-1· K-1 after sample preparation by injection molding. In addition, X-ray diffraction analysis revealed that the differences in the thermal conductivity, depending on the molding temperature during specimen preparation, were caused by variations in chain orientation within the same polymer. Based on the obtained results, it was concluded that LCPs are strong candidate matrix materials for thermally conductive composites; the suggested in-situ polymerization method could be applied practically to the polymerization of polyester-type LCPs. 相似文献
20.
《Field Crops Research》1996,48(1):1-9
Temperature is an important determinant of crop development rate (DR). Some reports have shown that the response of DR to temperature is nonlinear over a wide range. Others indicate that DR is affected by the amplitude of the diurnal temperature fluctuation. However, the nonlinearity between DR and temperature and the temperature amplitude effect are often confounded, as the amplitude effect can be explained by the nonlinearity. This paper investigates the effect of temperature amplitude per se on development to flowering in rice (Oryza sativa L.), using controlled-environment data for 16 cultivars. The response of DR to diurnally constant temperatures was quantified by a nonlinear model and subsequently used to predict days to flowering under diurnally fluctuating temperatures. The often large discrepancies between predicted and observed days indicated an effect of the diurnal temperature amplitude on DR. This effect was significant at different probability levels in 11 cultivars, but not in the other five P > 0.10). The trend of this effect, where significant, also strongly differed among cultivars: temperature amplitude accelerated flowering in one cultivar but delayed flowering in others. The nonlinearity between DR and temperature and the effect of the temperature amplitude can explain a large part of the often observed variation among environments for thermal unit requirements for flowering. 相似文献