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Comparison of Fiber Orientation Results of a Moldflow®-implemented pARD-RSC Model to µCT Scans
Fiber-reinforced polymers have gained popularity in various industries over the past years, as they allow the reduction of products' structural weight without compromising on performance. The material and mechanical properties of such polymer composites are mainly dependent on those of the fibers included in the polymer matrix. It is therefore crucial to be able to predict the fiber orientation in the injection-molded part during the design process. Simulation techniques offer an efficient and cost-friendly way to perform such predictions early on in the development process. However, accurate simulative predictions necessitate precise material models. Therefore, in this work, the prediction accuracy of three fiber orientation models are compared to experimental fiber orientation data obtained from high-resolution x-ray micro-computed tomography (µCT) scans for two different geometries. The models used to describe the fiber orientation in the Moldflow® simulation are a Solver API-implemented pARD-RSC model with shear-fitted parameters, an MRD model with Moldflow® default parameters and an RSC model with Moldflow® default parameters. Through the performed comparison, it was found that today’s state-of-the-art models are still unable to predict the fiber orientation for variant flow regimes and different part geometries accurately. This shortcoming was mainly highlighted for elongational flows.
Compounding Technology (Techniques and Tips) For Improved Performance and Productivity of Automotive
Ever since the first polymer applications were incorporated into the automobile in the 1960’s, OEM requirements for polyolefin based automotive compounds have pushed the performance envelope with respect to, for example, improved mechanical properties such as flex modulus, tensile strength, and heat distortion temperature; aesthetic properties such as surface quality; processing characteristics such as viscosity; and as always, cost. However, density was not a critical concern since the part being replaced was most probably made of metal. To attain required physical, esthetic and viscosity properties such as those listed above, compound formulations have become very complex. The main additives to the base polymer in early automotive applications such as a battery tray, were typically glass fiber and/or mineral filler for reinforcement. However, as manufacturers have continued to push vehicle weight reduction, they are re-evaluating specifications for current polymer-based applications/parts, i.e. bumpers, trim, etc., for future model years. In most instances, all the specified mechanical and flow properties remain the same, but density is reduced between 5 and 10%. Generally, this requires an extensive material reformulation to meet the new specifications. As part of most light-weighting reformulations, high bulk density filler content is decreased and replaced with multiple grades of polypropylene having a wide range of viscosities. These resins need to be melted and uniformly blended to provide, for example, strength from a high MW, high crystallinity component and good flow characteristics from a low MW grade. Additionally, any IM (impact modifier) needs to be dispersed and uniformly distributed. For reinforcement to be effective, fibers need to be unbundled as well as maintain a critical length during the compounding process. Minerals, depending on their structure, need to be distributed and/or distributed and dispersed. The co-rotating twin-screw compounder has long been the equipment of choice for such compounding functions. However, compounders still face processing challenges such as how to optimize the extruder set up to uniformly compound 1) diverse viscosity matrix polymers, 2) incorporate and disperse impact modifier, 3) unbundle and distribute fibers, and/or 4) feed, distribute and disperse a poor flowing, “sticky” mineral filler or possibly an easy to fluidize low bulk density talc while simultaneously maintaining an economically viable production rate. Additionally, the process can be challenged to maximize fiber length in high viscosity mineral filled formulations. This paper will review requirements for compounding automotive polyolefin compounds with an emphasis on recent innovations in Co-rotating Twin-screw technology that have enhanced product quality and productivity for these complex lightweighting material formulations.
Compressibility In Fused Filament Fabrication
Fused filament fabrication (FFF) is one of the most accessible and flexible additive manufacturing processes. However, it is plagued by consistency issues related to material deposition. The role of compressibility is explored with an instrumented nozzle to relate the observed printing pressure to variations in deposited road widths. Variations in road width are analyzed relative to those predicted using a double domain Tait equation (PVT model) for high impact polystyrene (HIPS). Compressibility was found a critical effect, varying the road widths by up to 50% when accelerating and decelerating. The effect of the speed of transient stress propagation was also investigated but found insignificant.
Computational Modeling of IR Heating of Composite-Material Parts
This paper explains the computational model developed in predicting the infrared heating of a composite material component. Computational Fluid Dynamics (CFD) technique is used in predicting heating behavior of a thermoplastic composite component. In-house testing facilities has been utilized to determine the radiation characteristic of the materials. The computational thermal model developed is validated by experimentally measured temperatures at key locations of sample plate during its heating. Comparisons between experimental data and numerical simulations showed good match between model & measurement. The developed model can be used as an effective tool in predicting the heater setting parameters for polymers/ composites heating in different application scenarios.
Creating A Skin-Core Structure With Foamed Phenolic Resins In An Injection Molding Process
The research of foam injection molding for thermosetting materials is still in an early stage. Recent studies focused on the process of volumetric underfilling, but open pore structures and gradients over the flow path were obtained. This paper gives an insight into a novel process variant, which makes the production of skin-core structures possible. It is shown, how an expanding mold technique enables the production of components with a solid skin layer and a foamed core in an injection molding process with phenolic resins. In an experimental design, packing pressure time and mold temperature are identified as the main influencing parameters. Their impact on the skin layer’s height as well as the surface quality of the specimen are discussed. Finally, a model description of the processes leading to the formation of these foam structures is proposed.
Degradable Plastics/Wood Hybrids For Sustainable Packaging Solutions
The costs for degradable plastics are in comparison to bulk plastics still high. To increase the market share of degradable-plastics-based products the reduction of the plastic used itself could be suitable option. To keep the degradable properties of the product suitable materials for a hybrid are wood or woodbased products like carton. In this paper, the combination of wood and degradable plastics to a hybrid material by overmolding was investigated. In this feasibility study the effects of injection molding on wood as an insert and the bonding strength between the two materials was analyzed.
Degradation Behavior of Aliphatic and Aromatic Biomass-based Copolyesters for Agriculture
This work concerns the synthesis, characterization and evaluation of enzymatic degradation kinetics in three biobased polymers: poly(hexamethylene succinate), poly(hexamethylene 2,5-furan dicarboxylate) and a copolymer containing hexamethylene succinate (HS) and hexamethylene 2,5-furan dicarboxylate (HF) units. All three comonomers are available from renewable resources, and their use in agricultural films and coatings would reduce the incidence of microplastics in soils, and could also provide functionality in controlled release applications. We find that copolymerization of the aliphatic and aromatic monomers reduces the crystallinity in the polymer, thus increasing the degradation rate.
Degradation of CPVC Sprinkler Piping Material By Simulated Sunlight and Uvb Light
The effect of simulated sunlight and ultraviolet (UVB) light on the chemical structure and tensile properties of chlorinated polyvinyl chloride (CPVC) was studied. Exposures were conducted in a Q-SUN xenon arc chamber and QUV accelerated weathering tester. CPVC tensile specimens were exposed for 1 week, 4 weeks, 8 weeks and 12 weeks and then analyzed using a tensile testing apparatus and Fourier Transform Infrared (FTIR) spectroscopy. The testing showed the CPVC material exhibited early degradation when exposed in the Q-SUN xenon arc chamber. FTIR analysis showed surface chemical structural changes as early as one week into the exposure and tensile testing showed apparent changes in elongation at break (70 % reduction) after 8 weeks of exposure in the Q-SUN xenon arc chamber (equivalent to 1344 hours of noon summer light) with a day light filter and 67.66% reduction in the elongation at break after 12 weeks of exposure in the Q-SUN xenon arc chamber with a window glass filter. CPVC tensile specimens when exposed in the QUV accelerated weathering tester exhibited discolored or stained surfaces.
Demonstration of a Preliminary Simulation Framework for Foam Blow-Molding using Commercially Available Blow-Molding Software
The use of foamed polymeric precursors for blow-molding and thermoforming applications is seeing increased use in the world of application development across a wide range of segments such as automotive, appliances, and packaging. Foam blow molding holds great potential for further enhancing lightweight solutions for complex hollow structures, while adding the potential of single-material solutions offering multi-functionality, e.g., thermo-acoustic isolation or damping. Unlike in the case of foam injection-molding, fundamental processing-structure-property interrelationships are not widely researched in the area of foam blow-molding. Modelling, simulations, and predictive engineering of foam blow molding processing are still in their infancy. Any simulation framework for this purpose needs to address the complex interplay between the matrix rheology, foam morphology and morphology evolution, and the resulting processability and thermo-rheological properties of the foamed product. Here, we report a preliminary simulation framework for foam blow molding, demonstrated in the context of foam extrusion blow molding. The framework addresses several important material and processing considerations. These include: (1) the initial foam morphology; (2) the nonlinear viscoelastic characteristics of the foamed melt; (3) the derivation of constitutive parameters for the foam – arriving at a homogenized representation of the foam rheological characteristics; (4) the implementation of blow-molding simulations using these parameters in a commercially available simulation software; and (5) finally correlating the local strains in the blow molded part to its morphology.
Design and Evaluation of Bicomponent Core-Sheath Die for 3D Printer Filament Feedstock Co-extrusion
Carbon based or inorganic fillers in 3D filament can enhance properties of 3D printed parts and are attracting considerable interest from academic and industry researchers, such as MarkForge, BASF, ColorFabb, and Graphene 3D Lab. Although 3D-tailored composites have been developed, very little work has been done on the production of advanced 3D filament feedstock for FDM. Work is needed on biomedical application filaments which require (i) high filler or nanoparticle loading, (ii) dimensional accuracy and (iii) superior surface finish. Current FDM filaments rarely exceed filler concentration of 10%, for example, in case of calcium phosphate without sacrificing quality. In this work, a melt-spinning die was designed with 2D FEM flow simulations to minimize interfacial flow instabilities. With the die, a co-axial 3D feedstock filament up to 20% filler concentration was spun. Tensile bars were successfully printed with 15% filler content and had similar tensile properties to neat PLA.
Design of A Novel Free-Rotating Mixing Sleeve For Single-Screw-Extrusion
This paper will present the conceptual design of a novel free-rotating mixing sleeve for single screw applications. In contrast to most of the currently available free rotating mixing rings (e.g. the TMR) which primarily have a distributive mixing effect, the mixing sleeve presented in this paper will focus on dispersive mixing. The variety of requirements on dispersive mixing make the structural design and the geometrical layout very complex. Therefore, a method is introduced to couple a full parametric 3D-CAD master model of the mixer with a 3D-CFD-simulation. The aim is to describe a set-up of an automated process to design and optimize the novel mixing element by defining several target figures.
Determination of Physical Properties of Fused Filament Fabrication Parts as Influenced by the Nozzle
A design of experiments using different nozzle diameters with varying road heights and shear rates (based on print speed) was done using lab-made polylactic acid filament. Subsequent tensile testing and calculation was done to obtain the main responses of ultimate engineering stress and tensile modulus. Linear models were made to determine the significance between the different dependent and independent variables. The main results show that larger nozzles, shorter layer heights, and lower shear rates provide stronger, heavier and stiffer fused filament fabrication parts.
Development of An Agile, Battlefield Additive Manufacturing Plant For Recycled Pet
The objective of the overall project is to conduct applied research that will lead to the development of an innovative agile manufacturing plant for onsite fabrication of recycled thermoplastic products at the US military’s forward operating bases (FOBs). The proposed manufacturing plant needs to be contained in 20-foot ISO containers for both shipment and operation. A study by the US Department of Defense (DoD) of base camp waste confirmed that the single largest source of waste plastics is Polyethylene Terephthalate (PET) from water and other beverage bottles. The on-going project to convert waste or reclaimed PET (rPET) to useful products is currently being conducted by Emc2 and the US Army Corps of Engineers and is being supported by the DoD’s Strategic Environmental Research and Development Program (SERDP) as a three year effort starting in June 2018.
Development of High Stiff Polypropylene Foam as an Alternative to Existing Polyethylene Foam Grades
The development of a high stiffness Polypropylene (PP) foam for use within the rotational moulding industry has been investigated by Matrix Polymers. The scope is to offer a stiffer and more advanced alternative to the current Polyethylene (PE) foams which are on the market. Matrix Polymers want to push the boundaries of current products and combine new technologies to produce a new material. Differing compositions of CBA (chemical blowing agents), various dry blends and compounds have been trialed alongside experiments into the CBA reaction time and expansion ratios. The availability of K-kord temperature logging equipment has been utilized alongside JUST RITE temperature labels, static oven machines and a rotational Ferry machine to develop the new material. All of the above has furthered understanding into the astonishing potential of this new material. Offering this product to the rotational moulding industry would be greatly beneficial to rotational moulders from around the world in a variety of applications, we understand the limits of rotational moulding are the lack of suitable polymers. This is something that Matrix continues to challenge.
Development of Innovative Biocidal Nanoparticles For Use In Plastics Technology
Increased demands on high-end materials focus the development on new functionalities such as biocidal effects, which are made possible by property changes in the nanoscale range of existing materials or by a combination of different material classes. Therefore nanoparticles, based on transition metal oxides have been synthesized in order to reach biocidal properties on plastic part surfaces. The influence of the nanoparticles on the thermal and mechanical properties have been characterized as well as the biocidal properties of the plastic part surfaces and of the nanoparticles itself.
Development of Shape Memory Thermoplastic Polyurethane (TPU)/Polylactic Acid (PLA) Polymer Blend
Shape memory polymers represent a family of stimuli-responsive materials that can be used in many applications. Polylactic acid (PLA) is a type of shape memory polymers that is biocompatible and biodegradable. By blending PLA with thermoplastic polyurethane (TPU), its shape memory effect would be improved. This study aims to optimize the shape memory effect of TPU/PLA polymer material systems and investigate the influence of material compositions and processing conditions on their shape memory effects. Blends were fabricated with different compositions and/or different thermal history. Experimental results revealed that the addition of TPU increased the recovery but decreased the fixity at the same time. Overall, the 65/35 TPU/PLA blend has the best shape memory performance. The duration of stretching at the transition temperature in the process of the test of the shape memory properties influenced the crystallization of samples. The sample could show a bad shape memory effect if the stretching time is too long.
Differences Between the Recycled Carbon Fibers Especially Regarding Product Quality
In the plastic industry, the modification of polymers with glass or carbon fibers is common to improve the product quality and properties. Particularly, the twin screw extruder is frequently-used for continuous compounding, preparation and processing of polymers. The steadily growing demand for fiber-reinforced thermoplastics and the high cost of the carbon fibers are the motivation for recycling. Furthermore, new laws (e.g. EU Waste Framework Directive and End-of-Life Vehicle Regulation) demand the recycling of the remains and the waste of the carbon fiber production.
Durability of Cellulose Nanomaterials under Industry Relevant Shear Stresses
The effects of high-shear flow on cellulose nanocrystals (CNCs) were studied to characterize potential impacts of industrial processing on these materials. A microcapillary rheometer was employed to study the rheological characteristics ofaqueous CNC suspensions at concentrations ranging from 1.5 wt% to 12.1 wt%.Increased cellulose content in the suspensions produced increased viscosities. A Sisko model was successfully fit to the data which display high shear Newtonian plateaus. Shear rate sweeps at these concentrations failed tofullyreduce to a master curve. Furthermore, repeated testing of the same sample volume at nearly 800000 s-1led to a permanent decrease in viscosityfor all samples.Atomic Force Microscopy (AFM) probed CNC morphology to observe any changes in the CNC dimensions which may have contributed to this phenomenon. AFM resultsindicate significant decreases in both height and length of the CNCsafter repeated testing at high shear rates.
Dynamic Variable Gate of Mold and its Application to Injection Molded Part Quality
As sensors evolve, their application has expanded. Mold related processes and technologies have become a focus of technology research and development. Mounting sensors in the mold cavity has become a trend in recent years. Since heretofore data has largely been limited to feedback data from the injection molding machine, control of the sensor data is the key to exploring the filling behavior of the molten melt in the cavity.In this study we created a dynamic variable-gate design in the mold. In combination with sensors to collect real-time data in the mold cavity during the injection stage, experiments were conducted to explore the course of shear heat and pressure drop generated by the melt passing through the gate when the gate thickness is varied. Therefore, the dynamic variable-gate design parameters such as gate thickness, advance delay time, and forward distance are discussed herein. To understand whether the gate thickness changes in the injection process, the influence of different parameters on the product shrinkage, product weight, and tensile strength are explored.
Effect of Coating Anisotropy on Scratch Behavior
Three-dimensional finite element method (FEM) modeling has been carried out in this study to investigatethe scratch-induced surface deformation and damage mechanisms in composite coatings applied on polymer substrate. Composite coating systems with anisotropic properties and variation in thicknessare considered in the numerical framework to study the influence of coating anisotropy and layer thickness on scratch behavior. The results show that coating anisotropysignificantly affectsthe scratch resistance of coating systems. Implications of the numerical findings on scratch resistance of coating systems are discussed.
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