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This study focuses on the filling behavior of resin transfer molding (RTM) process. By the visualization system, the flow patterns of resin during transfer molding were observed and the data were used to estimate the permeability tensor. In addition three-dimensional simulation were used to predict the filling behavior in thickness direction and the edge effect of the RTM process. The comparison between simulation and experiment result shows the capability of 3D numerical simulation on the filling behavior of the RTM process. The simulation tool would be helpful to obtain the optimal operating condition to reduce the trial-and-error time and materials.
This paper reports the database of mechanical properties of unidirectional carbon fiber reinforced plastic composites. The unidirectional carbon fiber prepregs which made through hot melt process were used as reinforcement and both polyamind6 (PA6) and epoxy were used as matrix to make CFRP boards through compression process. The mechanical and interfacial properties of 0 and 90 degree CFRP composites were investigated by tensile test and fractured surface observation. Fracture toughness was investigated by compact tension test.
A numerical study on the filling behavior of polymer melt into macro- and micro-cavities was performed using the finite element method. The simulation procedure consists of two steps; as the first step, pressure history data were exported from the macroscale flow simulation in which the numerical domain was considered as 7 inch LGP geometry without microfeatures, and next, the microscale flow simulation was performed using pressure data as the boundary conditions. The microscale domain contains single cylindrical microfeatures with a diameter of 30 ?m and a depth of 14 ?m on the nickel stamper with a thickness of 0.5 mm. The numerical results showed that the predicted final height of the microfeatures and the filling time at different positions agreed well with the experimental data.
By using dynamic mold temperature control in injection molding, parts with special features such as functional micro structures or high gloss surfaces can be produced in a one-step process. Due to limitations of available mold heating techniques, an innovative system using an externally robot-guided laser scanner was developed and implemented at the Institute of Plastics Processing (IKV) at RWTH Aachen University. High heating rates, a focused, discrete heating of specific cavity areas and the flexible, mold independent set-up are key aspects of the technology.
Near infrared spectroscopy was used in-line to determine the residence time distribution of polypropylene with the help of different tracers. Two twin-screw extruders, one single-screw extruder as well as different experiment alignments such as screw speed and their influence on mean residence time and especially residence time distribution have been investigated. It could be seen that with NIR the residence distribution time is easily measureable. Additionally the Young’s moduli and the tensile strength values of different produced polypropylene nanocomposite have been monitored and correlated to the NIR-spectra which have been collected simultaneously during the production on a co-rotating twin screw extruder. The results showed that both mechanical properties can be very well correlated with near infrared spectroscopy so a sophisticated quality control is possible.
With the growing use of co-injection molding process, it becomes essential to understand skin/core material distribution in the cavity for ensuring the quality of final product. In this study, warpage issue will be examined numerically and systematically by process effect and material combination in sequential co-injection development. Specifically, decreasing melt temperature or slowing down flow rate of 1st shot, which makes frozen layer thicker, can improve warpage problem. When the frozen layer is thicker, the core layer is more difficult to penetrate through the thickness direction. Thus, the melt is squeezed to advance in the flow direction, that forces melt go farther and better packing effect can be implemented accordingly. However, warpage becomes worse due to two used different materials with distinct properties mismatching while processing co-injection. To validate our simulation investigation, the experimental study will be performed in the near coming future.
Resin transfer molding (RTM) is a widely applied manufacturing method of composite materials. In RTM, permeability of fiber reinforcement varies with its geometric formation and affects the property of resin flow. Therefore, effective online estimation is crucial to achieve satisfactory quality product. In this work, a method of online measuring local permeability is proposed, which can deal with variation in local permeability caused by irregular arrangement of fibers. This study is divided into two stages. First, flow visualization was realized and all hardware was integrated to acquire information in resin filling. Second, local pressure and flow front location were substituted into the Darcy’s law, thus making online calculation of local permeability feasible. At the end of this study, the proposed methods are utilized in a trial RTM test to confirm their effectiveness.
This paper examines the recycling of sorted plastic offcuts produced during the manufacture of continuous carbon-fiber-reinforced polyamide 66 sheets. The idea is to process the offcuts so that they can be conveyed to a value adding application. For this study, the offcut is shredded into recyclate and processed by injection molding to produce specimens. The processing properties of the recyclate and the mechanical properties of the specimens are at the focus of the investigations. Good processability of the recyclate is achieved in the tests by using a stuffing device in the hopper of the injection molding machine. With optimum injection molding parameters, an outstanding tensile strength of 293 MPa is obtained in the tests.
The backmolding of continuous fiber-reinforced thermoplastics – so-called composite sheet – is based on the idea of combining the benefits of injection molding with those of semi-finished composite sheet. In this way it is possible to integrate the forming process for the composite sheet into the injection molding process and not only benefit from the outstanding weight-related strength of the composite sheet but also achieve a high level of stiffness by backmolding the part with rib-like structures. This study investigates the influence of key process parameters on the strength of the bond between the composite sheet and the backmolded thermoplastic component, based on a peel test.
By using supercritical carbon dioxide (Sc-CO2) as a foaming agent, the poly(lactic acid) (PLA) foams were prepared in a batch process using two different temperature modes. The crystallization and foaming behaviors of the PLA were investigated, putting emphasis upon the foaming behavior of spherulites. It is found that by tuning the saturation and foaming temperatures, the spherulites in PLA foams could present various structures, such as circular entities, stamen-like cell structures, and small cells (0.6 µm). Interestingly, a bi-modal cellular structure is observed for the sample foamed at 100°C saturation temperature and 170°C foaming temperature. Using the foaming temperature of 140°C, the samples prepared at 100 and 180°C saturation temperatures exhibit crystallinities of 42.7% and 6.8%, and corresponding expansion ratios of 1.9 and 49.8, respectively.
The process reproducibility during injection molding of micro components is often bought on an unnecessarily large dosing volume. To enable an economical production of micro components, a reduction of the material consumption is crucial. Therefore new production strategies need to be developed to reduce the required plasticized mass to a minimum while maintaining part quality at the same time. In the context of this paper, an innovative plasticizing method for micro injection molding is introduced, tested on its feasibility and analyzed in detail on its conveying and homogenizing characteristics.
The interest in renewable materials in car industry is growing dramatically. Natural fiber reinforced plastics (NFC) are an attractive solution, because of their interesting mechanical properties in combination to a good eco balance. One of the main obstacles to being used on a large scale in the car development process is the requirement that all components must proof that they meet product safety requirements and are fit for purpose through using CAE methods. The usage of CAE is a fixed established procedure in the automotive industry to meet today's challenging development times. The project NFC-Simulation, which is described in this paper, established a complete and integrated solution for the simulation of NFC components, from processing to crash simulation. In order to achieve these capabilities, many technical and scientific problems had to be solved in detail and the results integrated to a complete solution.
This article aims at conducting a detailed Computational Fluid Dynamics study to assess the efficiency of the conformal heating and cooling system associated in an injection molding process. The study involves characterizing the fluid flow and heat transfer behavior in an injection mold designed with conformal heating/cooling circuits. The key result of interest is to obtain uniform temperature distribution over the cavity profile. Further, the study involves identifying the important geometrical as well as flow parameters that have the significant influence on optimizing the heat up and cooling time which promotes uniform temperature distribution on the cavity profile. The formation of uniform temperature distribution, leads to the better quality and aesthetics of the injection molded parts. Importantly, molding defects such as knit lines, flow marks etc., are reduced to a greater extent compared to conventional injection molding processes.
Melt compounding using a co-rotating intermeshing twin screw extruder is the favored route to prepare polyamide (PA6)-multiwalled carbon nanotube (MWCNT)-composites. The melt compounding conditions influence the final properties of the resulting composites. Thus, this study discusses the influence of the process parameters screw speed, screw configuration, throughput and barrel temperature profile on the mechanical properties and the morphology of PA6-MWCNT-composites. The experimental investigations reveal, that the throughput and thus the residence time has the greatest influence on the mechanical properties, while screw configuration, screw speed and barrel temperature profile have only a minor effect. The area of agglomerates as indicator for the dispersion of the MWCNT shows no direct correlation to the processing parameters.
Addition of particles of low surface energy is shown to have a strong stabilizing effect on polymer foams. We examine two high melt index polymers, polystyrene and polylactic acid, foamed by chemical blowing agent. Both polymers show extensive coalescence and collapse when held in the melt state for extended periods. Addition of 5-10 wt% PTFE particles almost completely eliminates collapse, and greatly reduces coalescence. SEM shows that particles adsorb on the inner surface of the foam cells and creates a particulate shell that protects against coalescence. This appears to be a promising route to foam polymers with poor melt strength, especially in processing operations which involve slow cooling.
The total production costs of PET bottles are significantly affected by the costs of raw material. Therefore, stretch blow moulding industry intends to reduce the total production costs by an optimized material efficiency. The key factor is seen in a product specific preform design and well adapted process parameters. Due to a multitude of complex boundary conditions, the design process of new stretch-blow moulded products is still a challenging task and often based on empirical knowledge. Application of current CAE-tools can support the design process by reducing development time and costs. This paper describes an approach to determine optimized preform geometry and process parameters iteratively. The wall thickness distribution and the local stretch ratios of the blown bottle are calculated by a three-dimensional process simulation. Thereby, the wall thickness distribution is correlated with an objective function and preform geometry as well as process parameters are varied by an optimization algorithm. The approach is applied on an 0.5 litre PET bottle of Krones AG, Neutraubling, Germany. The investigations point out that the design process can be supported by applying the simulative optimization approach.
In this paper, the foaming behavior and thermal property of biodegradable poly(butylene succinate) (PBS)/nanosized calcium carbonate(nanoCaCO3) composites were investigated. This article focused on the study of the effect of nanoCaCO3 on foam morphology of PBS using supercritical CO2 as the foaming agent. The presence of nanoCaCO3 acted as nucleation site to facilitate the crystallization of PBS that results in the increase of PBS crystallization up to 63.63%. The effect of incorporation of the nanoCaCO3 particles on the thermal stability was quantified by the temperature at 5% and 10% weight loss. Along with the addition of nanoCaCO3, the temperatures at 5% and 10% weight loss of PBS/nanoCaCO3 composites are higher than pure PBS. The SEM results shows that with the addition of nanoCaCO3, the foam samples cell size decreased and cell density increased greatly.
In a prior work, a process model for the numerical optimization of blown film cooling systems was developed. This model is able to compute a realistic bubble film behavior depending on the cooling configuration. However, the optimization of a new cooling system requires proper initialization data to minimize the calculation period. In this paper, a prediction model is presented that can offer these data in a pre-optimization loop. The model is able to calculate an optimal cooling configuration with the corresponding film contour that is qualified for a detail process simulation. Furthermore, a novel cooling approach is optimized, using this model.
Generating basic material data information for natural fiber composites (NFC) for simulation requires uniform process parameters. This study is primarily concerned with the technical implementation of the uniform processing of different natural fibers (NF) such as sisal, wheat straw, hemp pellets, cellulose fibers and man-made fibers in extrusion and injection molding process. We were able to prove the possibility of compounding very different types of natural fibers and plastics under the same conditions by using optimized process parameters and by using a specialized extruder screw configuration.
An autosterile injection molding (AIM) process meets the requirement of sterility for medical single use products with the advantage to avoid additional sterilization procedures. However, autosterile injection molding is not yet common use within the polymer manufacturing industry. In contrast, autosterile manufacturing can be considered as state of the art within the pharmaceutical industry for many years. Therefore, injection molding within clean rooms is examined with regard to possible implementation as an autosterile manufacturing process. Sterility of polyoxymethylene melts are investigated in addition with the sterility of the injection mold during the manufacturing cycle and the contamination probability during the packaging period.
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