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This research aims to apply Computer Aided Design/Engineering (CAD/CAE) techniques for an optimized rubber injection molding condition using a case study of rubber steps used in motorcycles. The input parameters include both physical and mechanical material properties of natural rubber and operating conditions such as gating and runner positions. The simulated variables such as temperature, pressure and velocity profiles were founded and analyzed. The numerical results are correlated well with empirical data using the vertical injection molding machine. This research provides researchers the computational tool to obtain the optimized rubber injection molding.
Theresa Hermel-Davidock, James Seliskar, James Oelberg, May 2007
This paper will examine the scratch whitening resistance of PP rich, injection molded Thermoplastic Polyolefins (TPOs) for exterior automotive applications. Significant attention will be given to the influence of the molecular architecture of the polypropylene (PP) component on the surface morphology and resultant scratch whitening resistance of the injection molded part. Material parameters and surface crystallinity which contribute to enhanced scratch whitening resistance will be highlighted.
In this paper, we present results on shape memory behavior of polyurethane (PU)/clay nanocomposites. These nanocomposites were prepared via bulk polymerization method and contained exfoliated clay particles as revealed by transmission electron microscopy and wide angle X-ray diffraction method. The PU matrix contained a crystalline soft segment, which was responsible for shape fixity. The presence of clay decreased the crystallinity of soft segments and consequently shape fixity, but the magnitude of shape recovery stress increased, e.g., by 20% with only 1 wt% clay. The mechanism of reinforcement was studied by monitoring stress relaxation and phase separation.
To make sure the stable state of resin in the process optimization test, the process monitoring system (PMS) was applied in a wide range in this study. For each critical step of the test, the way to utilize the PMS depended upon the phenomenon in the mold and the purpose of the test. The dependent variables such as switchover point and holding time were properly set with the aid of the PMS. Based on the relationship of the state of the resin with pressure and temperature, a new PMS index was proposed. The index showed the best correlation with the part weight among various indices through the correlation analysis.
Carbon nanotubes (CNTs) were grown on the surface of carbon fiber using thermal chemical vapor deposition (CVD) technique. Ni is used as a catalyst. The coating of catalyst on the surface of carbon fiber was done by electroless dip coating technique. By performing structural characterization of CNT coated carbon fiber using scanning electron microscope (SEM) and transmission electron microscopy (TEM), the length and diameter of CNTs were measured and found to be ~9000 nm and ~40 nm respectively. Thermo gravimetric analysis (TGA) of as received and CNT coated carbon fiber samples in nitrogen atmosphere indicates that the CNT coated carbon fiber samples are thermally more stable. The improvement in storage modulus in CNT coated carbon fiber samples is observed in dynamic mechanical analysis (DMA).
P.J. Bates, M-E Druart, M. Chen, G. Zak, J. Billiet, May 2007
Laser transmission welding is a process used to join two thermoplastic materials based on their abilities to transmit and absorb laser energy. The influence of part thickness, glass fibre content, and line energy on the laser welding of a semi-aromatic polyamide was examined. Plaques of polyamide mXD6 were moulded at three different thicknesses (0.5 mm 1 mm, and 2 mm), a range of glass fibre contents (0, 30, 50 and 60%) in both natural and black. Lap welds were made using a Rofin Sinar diode laser in a contour welding mode over a range of line energies. The assemblies were tested in shear and the fracture surfaces examined using scanning electron microscopy.
The numerical prediction of three-dimensional warpage simulation during cooling process for injection molded parts before demolding is conducted in this paper. Similar to other warpage calculations, the energy equation for injection molded parts is solved together a thermal elastic models to investigate the shape deformation inside mold. Different from previous studies assuming melt cooling from solid state, the injection molded parts are cooled from fluidic state using a solidification model. Additionally, the influence of mold constrain is also taken into account.
Aaron P.R. Eberle, Donald G. Baird, Peter Wapperom, May 2007
In this paper we present a constitutive relation for predicting the rheology of short glass fibers suspended in a polymeric matrix. The performance of the model is assessed through its ability to predict the steady-state and transient shear rheology as well as qualitatively predict the fiber orientation distribution of a short glass fiber (0.5 mm, L/D < 30) filled polypropylene. In this approach the total extra stress is equal to the sum of the contributions from the fibers (a special form of the Doi theory), the polymer and the rod-polymer interaction (multi-mode viscoelastic constitutive relation).
Avraam I. Isayev, Changdo Jung, Kaan Gunes, May 2007
A novel method for the continuous dispersion of carbon nanofibers (CNFs) in a polymer matrix for manufacturing high performance nanocomposites was developed using an ultrasonically assisted single screw extrusion process. The effect of ultrasound on die pressure, electrical conductivity, rheological, morphological and mechanical properties of polyetherimide (PEI) filled with 1-20 wt% CNFs was studied. A reduction in the die pressure, percolation threshold and an increase in the viscosity, Young's modulus and electrical conductivity along with better CNF dispersion in nanocomposites was achieved through ultrasonic treatment.
A systematic study was carried out to investigate the effects of nanoscaled electroless nickel-phosphorous alloy coating on the thermomechanical properties of woven carbon fiber fabric reinforced polyester matrix composites. The electroless nickel-phosphorous coated carbon fiber fabrics with different coating time interval (0, 5, 10, 15, 20, 25, 30mins) were prepared. The polyester matrix was then used to manufacture weave carbon fabric/polyester nanocomposites using wet lay-up process. Dynamic mechanical analysis (DMA) studies were carried out in bending and tensile mode. Experimental results showed Maximum improvements in modulus for 30mins coating time reinforced composites. Dynamic mechanical analysis showed enhancement in thermomechanical properties. The nickel-phosphorous coated carbon fiber fabric composites showed a considerable improvement in the glass transition temperature (Tg).
Jingsong Chu, Andy Hrymak, Musa R. Kamal, May 2007
A micro-injection molding machine was used to obtain micro-moldings of polyethylene, in order to study the effects of processing conditions on some microstructural characteristics of the moldings. The processing variables were estimated, based on experimental data and on simulation results. Polarized light microscopy was used to evaluate morphology. Three-dimensional distribution of shrinkage was measured. Micro-mechanical properties (modulus and hardness) were measured with a nanoindenter. The microstructure and properties will be explained in light of the thermo-mechanical history.
When analyzing the thermal behavior of hybrid molds, normally fixed values for thermal characteristics are implemented. This paper will discuss the underestimated effect of temperature dependant heat characteristics of hybrid mold materials on the accuracy of 3D injection molding simulation via obtained results of a former PhD work and implementation of this knowledge into Moldex3D (M3D).A hybrid mold of a technical part was designed to analyze this problem. It also resulted in a better understanding of the mold design strategy and 3D simulation advantages for multiple material molds related to filling, warpage, cooling and final part quality.
G. Tosello, A. Gava, H.N. Hansen, G. Lucchetta, May 2007
The insufficient entanglement of the molecular chains and the stress amplification at the v-notch of a weld line compromise the mechanical strength of a plastic product, also in the micro scale. To investigate the influence of process parameters on the weld lines formation, a special micro cavity was designed and manufactured by ?EDM (Electro Discharge Machining). Weld lines were quantitatively characterized both in the two-dimensional (direction and position) and three-dimensional range (surface topography characterization). Results showed that shape and position of weld lines are mainly influenced by mold temperature and injection speed.
Laser welding has proved an appropriate method for joining plastic parts. The increasing trend towards greater freedom of design, integration of ever more functions, and therefore more complex modules is putting increasing pressure on joining technology, and is thereby promoting the development and introduction of novel technologies.Laser welding of plastics is a suitable complement to established joining processes, and thereby opens up new fields of application. This has been demonstrated by numerous applications for small and even for larger components.Compared to alternative joining methods the contact free method has the advantage that hardly any flash or no flash is being produced, which means that joints with a high quality visual appearance can be produced. The laser is clearly superior to alternative processes, even for joining 3D geometries produced by coupling to a robot. The heat-affected zone is only a few #m deep and reduces the risk of surface flaws.The following paper is a case study for the introduction of the Laser welding process for electro-pneumatic valves. It describes the process development from the initial tests to the In-Line integration in mass production.
Measurements and simulation of three birefringence components and of the gas/polymer interface distribution in gas-assisted injection molding (GAIM) of a tubular geometry are presented. The governing equations of the process are derived using a nonlinear viscoelastic model and solved using a hybrid finite element/finite difference/control volume method (FEM/FD/CV). The measurements were carried out on polystyrene moldings before and after annealing. Simulation and experimental results indicate that the birefringence is high in the gas penetration region and low in the region where the gas did not penetrate.
Zaneta Brocka, Ernst Schmachtenberg, Gottfried W. Ehrenstein, May 2007
Electron beam irradiation primarily leads to cross linking in the amorphous fraction of semi-crystalline thermoplastics. As a result, there is a change in morphology and an improvement in mechanical and thermo dynamical properties. This effect can be utilized for tribologically stressed parts as micro parts and gear wheels. These parts feature an unfavorable relationship of part/volume leading to a disadvantageous formation of morphology and crystallinity. Experimental work shows the potentials of radiation cross linked polyamides. Due to cross linking in particular the thermal-mechanical and tribological properties are shifted into a range, which enables the employment of this substrate for application at elevated temperatures. Furthermore, the investigations on PA6 and PA66 show that a lower crystallinity degree leads to better results of cross linking via electron beam radiation and to an improvement of abrasion resistance.
Jan Spoormaker, Erik Andreassen, Anton Heidweiller, May 2007
The new European Failure Analysis and Prevention Special Interest Group (FAPSIG) is creating a database with failure cases. The members share this database and contribute with their own failure investigations. The two main groups are Failure Causes and Failure Mechanisms. Failure Causes are subdivided in: Stress concentrations, low mass and/or mould temperature, highly stressed weld lines, faulty ribbing; too high stiffness of construction elements, incorrect joining, and incorrect material selection.Failure Mechanisms are subdivided in: Creep and stress relaxation, wear, fatigue, UV degradation, chemical attack, environmental stress cracking.The paper will present some examples for designers of plastic products.
Chelsea A. Braybrook, Jennifer A. Lee, Philip J. Bates, Marianna Kontopoulou, May 2007
A newly constructed sliding plate rheometer (SPR) is used to investigate the high frequency linear viscoelastic properties of two polypropylene (PP) resins with widely differing melt flow rates. Extrapolation of rheological measurements obtained on a traditional parallel plate rheometer to frequencies obtained on the SPR, through use of the generalized Maxwell and Cross models, was used to assess the performance of the high frequency SPR. Good agreement between the extrapolated and measured data demonstrates the ability of the SPR to measure the high frequency rheological properties of PP.
Suchada Rianmora, Chana Raksiri, Supasit Rodkwan, Kunnayut Eiamsa-ard, May 2007
Development in design of mould using reverse engineering can reduce lead time and increase the quality of mould inspection. For two methods used: touch probe on machining center and portable arm coordinate measuring machine, these are used along software that is capable of measuring three-dimensional coordinate and analyzing the results. The first inspection is done on the machine during production (inline) then another is examined after production (offline). The experiment result demonstrates in terms of accuracy there is no significant difference between two measurement methods. Nevertheless, the portable arm CMM has an advantage in its simplicity, and require less operation and lead time.
Ralf Kühn, U. Burkhardt, Peter Heidemeyer, May 2007
Melting and incorporation of high viscous particles into a low molecular matrix is a difficult process due to differing requirements for melting and homogenizing. Melting is preferably done by using high shear rate and stress in combination with a small residence time. These facts lead to a fast turning small machine. Homogenizing on the other hand requires elongational flow, high viscosity and a significant amount of residence time which leads to a low revolution speed. By using a two step compounding system one can meet the differing constraints at the same time. Optimization of efficiency in pressure build-up can be done effectively by using state of the art CFD calculation methods.
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