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Pipes in heat exchanger systems are usually made of metallic materials to achieve a high level of thermal conductivity and thus high efficiency. However, substitution with polymer materials has a great potential. Plastics save weight, can be produced at lower cost and emissions, and are ideal for use in corrosive or chemically aggressive environments, where most metals fail. The challenge, however, is their much lower thermal conductivity in comparison. To reduce this disadvantage, fillers are used to transport thermal energy through the less conductive polymer matrix. In fact, high filler ratios are required to achieve an acceptable level of thermal conductivity for heat exchanger systems. However, these high filler ratios have a significant impact on the material properties of the polymer, such as the flexibility, which is drastically reduced. The result is a brittle material with limited suitability for use in heat exchanger systems. This paper describes a novel approach to effectively increase the thermal conductivity of polymer materials by optimizing the orientation of anisotropic filler particles by die design. Standard pipe extrusion dies result in continuous shear forces in the direction of extrusion. Accordingly, the resulting filler network has a higher thermal conductivity in the axial direction of the pipe than radially through the pipe wall. However, radial heat transfer is essential in pipe heat exchanger systems. To improve this, various die designs for targeted radial alignment of filler particles are discussed in this paper. Furthermore, the potential for improvement of the die designs is investigated. So far, the most efficient die design achieves an increase in thermal conductivity of up to 74 % compared to a standard pipe extrusion die. [ABSTRACT FROM AUTHOR]

Numerical process simulation is an established development tool for the design of injection molding processes. However, commercially available simulation software focuses primarily on the filling process in the mold and makes various simplifications. Due to these simplifications, the non-consideration of disturbing influences, as well as the differing boundary conditions within the simulation, the result of the real process often deviates from the simulation result. To enable an injection molding simulation that is closer to reality, the aim of this work was to carry out an analysis of the current discrepancies between a real injection molding process and the simulation of this process. For this purpose, a design of experiments was carried out in the simulation and compared with the corresponding injection molding experiments. Relevant process variables such as the injection pressure or the cavity pressure as well as the parts weight were used as target variables for the analysis to compare the results from the experiments with the simulation. [ABSTRACT FROM AUTHOR]

Natural rheologic balancing is being state-of-the-art in developing polymer melt channels for extrusion dies or hot runners in injection molding. For this, flow path lengths and channel diameters in a manifold system are defined identical on all paths and thus those channels are considered to be identical in pressure drop and cavity filling, respectively in mass flow distribution. However, the changes in direction of the melt flow due to the deflection of the melt are in most cases neglected but have a significant impact on the flow field in downstream components. Strong deflections, as they occur in conventional manifold systems, can be avoided by the use of additive manufacturing methods. However, the bionic design leads to curved melt channels which, when naturally balanced, may differ completely from one another regarding their overall course and curvature. Therefore, unequal mass flow distributions or cavity fillings occur in such geometries. The aim of this paper is to investigate the influence of channel curvature on the balancing of additively manufactured melt channels. For this purpose, a test specimen is designed and the curvature collectives along the neutral fibers are evaluated. The overall objective is a more specific balancing with respect to the mass flow distribution. The results indicate the necessity of considering the channels' curvature in the designing process in order to achieve a homogeneous melt distribution. [ABSTRACT FROM AUTHOR]

Elastomeric polyurethane components are used in many applications to solve problems of vibration damping or compensation of geometric misalignment. The material damage induced by thermo-mechanical stress collectives significantly influences the vibration behavior of the entire system. However, in product development, the consideration of progressive material damage is only possible to a limited extent. A possibility to face this problem is the coupling of a material model with a damage accumulation model to describe a damage progression in simulations. For this purpose, fatigue tests are performed on specimen level to generate damage parameters. The parameter sets are then used to calibrate a damage-dependent material model. A progress of material damage is calculated by a nonlinear damage accumulation model. The results are transferred to a demonstrator component using the finite element method to map the influence of progressive material damage on the entire component. [ABSTRACT FROM AUTHOR]

Electroplated plastic parts are based on multiphase materials such as ABS and PC/ABS. Particularly in the automotive industry, the quality standards for coated parts are high. Unfortunately, mineral-filled polyamide, as an alternative to the standard ABS-based materials, has a high scrap rate of 30 %. The injection molding process in particular influences the surface layer of the plastic part and thus the final quality of the bonding to the metal. Since these interactions are very complex and experimental trial and error is costly, it is desirable to use simulation to identify critical geometries and process settings. Unfortunately, such an analysis is only possible to a very limited extent with the commercially available injection molding simulation software. At present, the flow can only be calculated in a simplified way using the suspension material properties. An evaluation of the particle distribution is not possible. The aim of this paper was to develop an approach to simulate the transient multiphase flow problem considering the interaction between particles and the polymer matrix as a function of injection molding process parameters. For this purpose, the Eulerian model was used in ANSYS Fluent. This complex multiphase model allows the solution of the governing equations for each separate phase. Furthermore, the boundary conditions of the simulation were derived from previous simulation, and they were integrated into ANSYS with user-defined functions. In the future, the approach will be used to evaluate the influence of injection molding process parameters on the orientation and distribution of the particles in the surface layer. This should increase the understanding in the processing of mineral-filled polyamide in order to minimize scrap production. [ABSTRACT FROM AUTHOR]

Blown film properties are predominantly defined during bubble formation due to simultaneous stretching and cooling of the polymer melt. Consequently, a promising prediction of film properties requires a precise description of these influencing processes. In this paper, a process-oriented approach for the simulation of these influences during film blowing is presented. The measured bubble contour, representing stretching, and the measured temperature profile, representing cooling, were considered as key simulation input. On that basis, the simulation model determined the complete film blowing process. For this, the common three principles, namely membrane theory, a constitutive equation and the continuity condition, were used. The calculations were performed by means of an iterative optimization procedure. Different operating conditions for film blowing were simulated and compared. Eventually, simulation output variables may serve for enhanced prediction of resulting film properties. [ABSTRACT FROM AUTHOR]

For years, the design of extrusion dies has been based on proven geometries, such as spiral mandrel manifolds for blown film extrusion. Common designs are based on patents originating in the 1960s which is why they are very limited by the constraints of conventional manufacturing processes. Considering current capabilities of additive manufacturing technology, there is potential for thermo-rheological optimization of melt-carrying channels of extrusion dies by widening geometrical degrees of freedom. Within a former project an additively manufactured demonstrator extrusion die consisting of a primary and secondary distribution has successfully been built and experimentally approved. However, the design of this geometry is entirely based on geometrical constraints such as cross-sectional area, lead curve length and local curvature. By, e.g., minimizing the melt leading channels' curvature a gentler deflection can be achieved. Nevertheless, the resulting flow behavior cannot be quantified directly and is only a result of a geometrical optimization. The aim of this paper is to introduce an approach on how to completely consider and assess the flow situation during the phase of designing by evolving the previously developed geometrical-based optimization to a CFD-based one taking the actual flow situation inside the die into account. This is done by establishing an automated optimization which first generates a population of numerous variants using parameters integrated into the CAD model. The optimization then automatically evaluates the variants by using a genetic algorithm following biological principles of evolution and by using CFD calculations and quality criteria specifically adapted and developed for this kind of optimization and geometry. Initial concepts show that this optimization setup results in multiple flow optimized designs which can be chosen from to concretize the final design of the extrusion die. [ABSTRACT FROM AUTHOR]

Plastic films make a valuable contribution in many areas due to their economic and technical advantages. To meet the associated requirements, complex combination of film properties must be achieved. For this purpose, varied materials are combined with each other. However, to ensure the overall function in use, the individual layers in the films must not separate from each other. The long-term stability can be seen as an important quality criterion for the composite. For a successful bond, the surface tension should be as high as possible at the interface and consist of equal disperse and polar fractions. However, there are material-specific differences. As a result, a bond between the partners is often not possible or it dissolves after a certain initial adhesion. In practice, this is often remedied by primers and adhesives that create a chemical bond between the materials. This use is associated with disadvantages, for example, there are increasingly stricter requirements due to new restrictions on the use of raw materials used in the primers and adhesives. The presented approach in this work to overcome these deficits is to treat the plastic melt of the partner with lower surface tension as it leaves the extrusion die with atmospheric pressure plasma and use it for a film composite free of adhesion agents and adhesives. The focus of the investigations presented here is on long-term stability of the activation effect. For this purpose, the produced samples were stored for up to 504 h. This was accompanied by a contact angle measurement to determine the surface tension according to the Owens-Wendt-Rabel-Kaeble method and an Infrared Spectroscopy to detect chemical changes. It was shown that the plasma treatment was successful on the one hand, but that the associated activation decreased over time. The initial state was not reached again. [ABSTRACT FROM AUTHOR]

Elastomer components are used in many technical applications due to vibrations and impacts. They are usually manufactured by the vulcanization process, which is more time-and energy-consuming than other plastics processing procedures. In addition, consistent product quality can be ensured through process reliability. Society goals such as sustainability and recycling can be met by using alternative materials such as thermoplastic elastomers (TPE). The focus is already on substituting elastomers with TPEs. Up to now, the requirements have often been derived from static properties, so that application-specific design with regard to dynamic properties has not been carried out. This paper contains an investigation of selected TPEs in relation to static and cyclic properties. First, the requirements for an elastomer material are analyzed and a reference material (natural rubber) is defined. Subsequently, a material screening is carried out and a pre-selection is made. The focus is on TPEs that are processed without vulcanization process. The materials are characterized based on laboratory measurements. Furthermore, static tensile tests and cyclic short-time tensile tests are carried out. The static and dynamic properties are evaluated and then compared with the reference material. In conclusion, an overview of promising materials is given and a group of materials is selected for following fatigue tests. [ABSTRACT FROM AUTHOR]

Elastomer-fiber reinforced plastic hybrid materials (E-FRP) provide potential for many future lightweight applications. Suspension and powertrain components in hybrid design can be optimized in terms of stress absorption by using elastomer interlayers to decouple the highly stressed fiber composite areas. First prototype runs with hybrid drive shafts have demonstrated a significantly increased mechanical performance compared to conventional composite structures. However, the material properties have not been sufficiently verified for use in the targeted application fields at this stage of development. To increase the technology readiness level of the E-FRP material, systematic experimental testing is necessary for the qualification of materials and production processes. In this study, a procedure for characterizing the material properties for the elastomeric interlayers is presented. First, the maximum principal stresses occurring in the application are determined via finite element simulations. A subsequent material characterization under dynamic loading is carried out for 2 elastomeric polyurethane hot cast systems. The usability of the hysteresis measurement method is demonstrated and characteristic values are determined and evaluated. An outlook on further application of the method is given and relevant material parameters for the selection of suitable materials are discussed. [ABSTRACT FROM AUTHOR]

Injection molding processes are influenced by internal and external disturbances such as machine wear or batch fluctuations. The goal is to detect these fluctuations and, in the best case, to correct them through quality prediction and process control using machine learning algorithms. However, machine learning models are only capable of doing this if the effects are included in the training data. If the process changes, the models lose prediction performance until they are no longer suitable for the new situation. This is called concept drift. In injection molding, sooner or later a process change occurs, so reliable detection is required. The objective of this paper is to evaluate different concept drift detection methods for injection molding applications. Nine different algorithms for concept drift detection were evaluated. For this purpose, disturbances were intentionally added to a stable process, which had to be detected by the algorithms. For example, the viscosity in the material was affected by adding material with higher residual moisture to represent batch variations. A total of 1600 injection molding cycles were carried out in three different experiments. [ABSTRACT FROM AUTHOR]

In single-screw extrusion, a uniform melt temperature distribution as well as a sufficient material homogenization are essential for an excellent quality of the final product. Therefore, mixing elements are used at the end of the extruder screw to generate the needed shearing and deformation of the polymer melt. CFD-simulations (Computational Fluid Dynamics) are the most common tool for the design and optimization of mixing elements, but the modeling and evaluation of distributive mixing processes in numerical simulations is a well-known problem. In this study, two different approaches for the prediction of the distributive mixing quality were evaluated: the change of the mean distance of streamlines on pre-defined cross-sections and a passive scalar integrated into the numerical solver. For this purpose, various flow simulations of a Block-Head-Mixer were performed and compared. The results show that the passive scalar has advantages over the evaluation by mean distance of streamline positions, especially regarding the integration into the simulation environment and when used for longer mixing sections. [ABSTRACT FROM AUTHOR]