Injection-molded Plates Research Articles

3D Printing of Flow Profiles for Inspection Chambers and Manholes

For years the way of producing a flow profile for Inspection Chambers and Manholes could be divided into 3 methods: Injection moulding, Roto moulding and Hand assembling. For the standard orientations, for example straight through and cross, the IM profile integrated with a base is by far the best option. But for nonstandard configurations; different orientations, inlet heights and inlet sizes, the only option is to hand weld them together from injection moulded parts, pipes and plates. This is a time- consuming way of producing with high production cost and often aesthetic-wise of a challenging level. This is not necessary anymore after the introduction of 3D printing as a new production method for flow profiles in chambers and manholes. 3D printing is in many industries an accepted production method which can produce parts of high quality and high accuracy. The printing systems have faced a huge development in the last 10 years and prints are often close to perfection. The only disadvantage of these printing systems is the maximum size of the print. But since the introduction of 3D robot printing, products with a diameter of 1 meter can be printed without any problem. 3D robot printers were up to recently, used for prototypes, one- off products and art objects. Now a production area is created on which multiple products can be produced in a row without human interference. The most common materials used for 3D printing are ABS and PLA. These materials have good adhesion, almost no shrinkage and a good appearance. Unfortunately, these materials are not common in our industry. We need PP, PE or PVC. While our manholes and inspection chambers are from PP, we also need PP flow profiles. The advantage of using a 3D robot printer is that it uses granulates instead of filaments or special powder. This makes the material cost part almost equal to injection moulding. Another advantage is also that recycled material can be used. Own scrap can be used but also waste from other markets. The main reason that flows profiles are ideal for 3D printing is that nonstandard flow profiles are very labour-intensive. So, 3D printing really helps out here. Besides that, there is a lot of freedom in design. This helps to design in such a way, that the final profile is hydraulically optimal. This prevents the overflowing of manholes during heavy rain showers. Of course, these products should fulfil all requirements of the EN13598-2. Even though major development steps have been made in 3D printing during the last 5 years, 3D robot printing is still in the exploring phase and we find many hurdles on our way. This paper will show how our industry can use 3D printing and what are the pros and cons.

Evaluation of wall thickness effect on tensile properties of injected short fiber reinforced polymers

The aim of this paper is to analyze the effect of increasing the wall thickness in injection molded short fiber reinforced polymer (SFRP) parts, focusing mainly on tensile strain and tensile strength, as these are the most used characteristics for structural analyses. The phenomena that makes this evaluation of interest has to do with the microstructure of SFRP injection molded parts and how the fibers get oriented along the flow direction at superficial depths with an increasingly less aligned structure down to the mid plane/surface. By increasing the injected part wall thickness the ratio between the thicknesses of highly oriented layers and poorly oriented layers decreases, thus the tensile properties of the material should suffer a decrease as well.In order to study the mentioned hypothesis two types of materials were tested, PPA GF33 and PPS GF40, dog-bone type specimens were cut at different angles to the flow direction from injection molded plates of 2 and 3 mm wall thickness values. The tensile strains were recoded using a video extensometer and material data was calibrated using Digimat MX reverse engineering module and Ansys properties homogenization tool and finite element solver.

Hygromechanical Behavior of Polyamide 6.6: Experiments and Modeling.

This paper investigates water absorption in polyamide 6.6 and the resulting hygroscopic swelling and changes in mechanical properties. First, sorption and swelling experiments on specimens from injection molded plates are presented. The observed swelling behavior is dependent on the melt flow direction of the injection molding process. Additionally, thermal analysis and mechanical tensile tests were performed for different conditioning states. The water sorption is accompanied by a decrease in the glass transition temperature and a significant reduction in stiffness and strength. Next, a sequentially coupled modeling approach is presented. A nonlinear diffusion model is followed by mechanical simulations accounting for swelling and concentration-dependent properties. For the mechanical properties, the notion of a "gap" temperature caused by the shift of the glass transition range due to water-induced plasticization is employed. This model enables the computation of local moisture concentration fields and the resultant swelling and changes in stress-strain behavior.

Short Flax Fibres and Shives as Reinforcements in Bio Composites: A Numerical and Experimental Study on the Mechanical Properties.

The complete flax stem, which contains shives and technical fibres, has the potential to reduce the cost, energy consumption and environmental impacts of the composite production process if used directly as reinforcement in a polymer matrix. Earlier studies have utilised flax stem as reinforcement in non-bio-based and non-biodegradable matrices not completely exploiting the bio-sourced and biodegradable nature of flax. We investigated the potential of using flax stem as reinforcement in a polylactic acid (PLA) matrix to produce a lightweight, fully bio-based composite with improved mechanical properties. Furthermore, we developed a mathematical approach to predict the material stiffness of the full composite part produced by the injection moulding process, considering a three-phase micromechanical model, where the effects of local orientations are accounted. Injection moulded plates with a flax content of up to 20 V% were fabricated to study the effect of flax shives and full straw flax on the mechanical properties of the material. A 62% increase in longitudinal stiffness was obtained, resulting in a 10% higher specific stiffness, compared to a short glass fibre-reinforced reference composite. Moreover, the anisotropy ratio of the flax-reinforced composite was 21% lower, compared to the short glass fibre material. This lower anisotropy ratio is attributed to the presence of the flax shives. Considering the fibre orientation in the injection moulded plates predicted with Moldflow simulations, a high agreement between experimental and predicted stiffness data was obtained. The use of flax stems as polymer reinforcement provides an alternative to the use of short technical fibres that require intensive extraction and purification steps and are known to be cumbersome to feed to the compounder.

ガラス短繊維強化PPS樹脂の繊維配向分布を考慮したマイクロメカニックスに基づくX線応力評価

The stress in polyphenylene sulfide (PPS) resin reinforced by glass fibers of 26 mass% was measured by the diffraction method using synchrotron with energy of 18 keV. The stress in the matrix was determined by the sin2ψ method with iso-inclination optics of transmitted X-ray diffractions. Tensile coupon specimens were cut from the skin-layer of injection molded plates in three directions, parallel, perpendicular and 45°, to the molding direction. The matrix stresses in the loading and transverse directions of specimens were measured under several uniaxial applied stresses. They changed proportionally to the applied stress. The proportional constants of the matrix stresses to the applied stress were determined, and named the stress-partitioning coefficients. The elastic constant and the matrix stress of the composite were calculated theoretically using micromechanics for two cases of fiber orientation: unidirectional (UD) and varied orientation distribution (VD). Fiber orientation tensor was determined from microscopic measurement of the cross-sectional shape distribution of fibers. Compared with the calculation based on UD fiber orientation, the analytical values based on micromechanics considering the variation in fiber orientation are closer to experimental values of elastic constants and stress-partitioning coefficients.

Mean Value-Amplitude Method for the Determination of Anisotropic Mechanical Properties of Short Fiber Reinforced Thermoplastics

Short fiber reinforced thermoplastics show distinct anisotropic behaviors due to their microstructure. The mechanical testing of specimens cut from injection molded plates at different angles to the injection molding direction reveals direction-dependent properties. However, these results are an average value for the tested cross section, which in more detail has a core-shell microstructure. When analyzing the stresses and deformation of a structural component, the local anisotropy will be very different compared to these tensile specimens. Therefore, a methodology is needed to transfer the properties obtained by mechanical testing to the local properties of an injection molded component. The core-shell microstructure and tests with different specimen thicknesses enable the determination of microstructure-dependent material properties. This paper presents a method using a mean value representing isotropy and an amplitude applied to the mean value to determine orientation-dependent mechanical properties. The amplitude in turn depends on the degree of anisotropy. The method is applied for extracting the anisotropic Young’s modulus of the core and shell layer of short glass fiber reinforced polyamide 46. The results obtained by this method and their reliability are discussed.

Use of a digital image correlation method for full-field shrinkage measurement in injection molding

An original methodology using Digital Image Correlation (DIC) has been designed to precisely measure full-field shrinkages of injection molded polymer plates and then to give the opportunity to compare quantitatively extensive numerical simulations to experiments. The principle of the methodology is based on the full-field strain determination between a reference image of the mold and that of injection-molded parts, which are 275 × 100 × 2.2 mm3 plates. To allow for DIC calculation, 50 µm-depth engravings were machined by electro-discharge process at the surface of the mold. The result of the analysis is a 2D full-field shrinkage map over the whole plate surface (i.e. flow and transverse), with a standard deviation of 0.03%. The marking density has been shown to have a roughly linear influence on the precision of shrinkage measurement. This methodology allows the quantification of the effect of several injection parameters on in-plane shrinkage fields: holding pressure, injection flow rate and direction, geometry of injection gates, or geometrical constraints. Once the best set of parameters of material constitutive laws is identified for the simulation of polymer plates, the simulation procedure is ready to be applied on more complex 3D geometries.

Quasi Static and Fatigue Properties of Long Carbon Fiber Reinforced Polyamide

In this experimental work, the quasi static and fatigue properties of a 40 wt.% long carbon fiber reinforced partially aromatic polyamide (Grivory GCL-4H) were investigated. For this purpose, microstructural parameter variations in the form of different thicknesses and different removal directions from injection-molded plates were evaluated. Mechanical properties decreased by increasing misalignment away from the melt flow direction. By changing the specimen thickness, no change in the general fiber distribution pattern transversal and normal to the axis of melt flow was observed. It has shown that with increasing specimen thickness the quasi static properties along the melt flow direction decreased and vice versa resulting in superior properties normal to the melt flow axis. At around 5 mm, an intersection suggests quasi-isotropic behavior. In addition, the fatigue strength of the material was significantly higher in the flow direction than normal to the flow direction. No change in fatigue life was observed while changing specimen thickness. The Basquin equation seems to describe the effect of stress amplitude on the fatigue strength of this composite. Scanning electron microscopy was used to investigate fracture surfaces of tested specimens. Results show that mechanical properties and morphological structures depend highly on fiber orientation.

Characterisation of the spherulitic microstructure of semi-crystalline thermoplastics

Microstructure, as the connection between process and material properties in semi-crystalline thermoplastics, plays a crucial role in fabricating high-quality prats. Hence, it is essential to consider the microstructure by predicting the component properties. An integrative multi-scale simulation chain on an ICME platform was previously developed and successfully applied to predict the local, microstructure-dependant, effective elastic and thermal properties of an injection moulded plate from the isotactic polypropylene over its cross-section. However, the calculation time of several hours for small volume elements at the microscale seems to be an obstacle to employ it in real cases. Data-driven models, such as artificial neural networks are meant to be employed in the presented paper to solve this problem. The focus here is on the spherulitic microstructure of semi-crystalline microstructure predicted by the simulation in-house-developed software SphaeroSim as the link between solidification simulation and homogenisation. To build data-driven models parallel to these two simulation tools, the microstructure must be characterised, and meaningful features need to be extracted from it. This work aims to present general features for the characterisation of a spherulitic microstructure and build a data-driven model parallel to the solidification simulation, predicting the proposed features by a given cooling temperature history.A set of two-dimensional (surface area, circumference, Feret diameter, long Feret diameter, form factor, convex circumference, convexity, equivalent diameter and form deviation) and three-dimensional (volume, surface area, aspect ratio and sphericity) was calculated for a data set of about 500 simulations. Their distribution suggests that almost all of the spherulite have an ideally spherical shape. Therefore, some of the features can be replaced with each other. The achieved accuracies for each data-driven model relating to a predicted feature shows the great potential for substituting the original simulation tools for data-driven models, to immensely decrease the prediction time while keeping the high prediction accuracy.

Effect of Neutralizer on Transparency of Nucleating Agent-Containing Polypropylene

The effects of neutralizer species on the transparency of injection-molded plates were studied using isotactic polypropylene (PP) containing a crystal nucleating agent—i.e., 1,3:2,4-bis-o-(4-methylbenzylidene)-d-sorbitol (MDBS). A plate containing lithium stearate (StLi) was more transparent than one containing calcium stearate (StCa) when the MDBS content was 0.1 wt. %. The addition of StLi accelerated the formation of MDBS fibers and the crystallization of PP. However, when the MDBS content was 1.0 wt. %, StCa improved the transparency more effectively than StLi. These results indicate that the combination of an appropriate amount of MDBS and the correct neutralizer species is critical for enhancing the transparency of injection-molded PP plates.

Effective elastic modulus of foamed long glass fiber reinforced polypropylene: Experiment and computation

The cross-section of an injection-molded plate of foamed long glass fiber reinforced polypropylene was analyzed using scanning electron microscopy. The distribution of the glass fiber orientations and the microcellular structure in the thickness direction were also studied. A multilayer representative volume element was constructed based on the fiber orientation tensors and the cell distribution. Nested and two-step homogenization methods based on the Mori–Tanaka and Voigt models were used to homogenize each layer of the representative volume element. Finally, classic laminate theory was used to obtain the effective elastic modulus of the material. The computed elastic moduli of the single-layer and multilayer representative volume element models with different loading directions predicted by the homogenization and finite element methods were compared with the experimental results. We found that the constructed multilayer representative volume element model can predict the elastic moduli of the foamed glass fiber reinforced polypropylene effectively and that the predicted results were accurate and stable.

Injection moulded composite bipolar plates for a portable hydrogen fuel cell charger

Fuel cells are electrochemical devices that convert the chemical energy of a reactants directly into electricity and heat with high efficiency. Proton Exchange Membrane or Polymer Electrolyte Membrane (PEM) fuel cells are one of the most common type of fuel cells. In a convection PEM fuel cell, the oxygen from air is introduced to the cathode and hydrogen is introduced to anode. Between the anode and cathode electrodes is sandwiched the polymer electrolyte membrane. The hydrogen molecules break apart into protons and electrons due to the reaction helped by catalysts. The protons travel through the membrane to the cathode and electrons travel to an external circuit. At cathode side the protons, electrons and oxygen molecules combine to form water. Research work was directed to the study of hydrogen fuel cell power systems for portable applications. Last decade the industry developed portable power systems based on hydrogen fuel cell, mobile telephone chargers, vehicles energy supply. In this paper are presented the experiments with a hydrogen fuel cell stack in which were assembled resin filled graphite bipolar plates and then injection moulded polymeric conductive composite bipolar plates and results were compared concluding that injection moulded bipolar plates could represent an attractive alternative in building efficient fuel cell portable power systems.

Investigation of fibre orientation and notch support of short glass fibre reinforced thermoplastics

In this paper, the effect of anisotropy on notches for a PPA-GF50 is discussed. For this, fatigue tests on specimens with boreholes at the centre, extracted from injection moulded plates, have been performed. Different, orientated layers, lead to anisotropic material behaviour along the notch. Simulations highlight the local stresses, including stress gradients. Nevertheless, the stress gradient along notches evoked by anisotropy, isn’t considered in common gradient models for notch support. Therefore, a novel method to take the effect of the local fibre orientation into account is proposed. However, experiments show a notch radius influence in fatigue strength and fibre orientation effect on notch support. The consideration of the new findings allows a more precise lifetime assessment for notched, anistoropic materials.

Capability of Scratch Testing − A View on the Influence of Injection Molding, Water Absorption, and Blend Systems of Polymeric Materials

Scratch tests have been performed on a set of different ductile and brittle thermoplastics to investigate the influence of injection molding, water absorption and blending on the indentation depth during scratching and hence the scratch resistance. For the measurements a universal surface tester (UST) has been used which allows to control the normal force between 10 and 1000 mN and the velocity between 0.01 and 2.5 mm/s during scratching while at the same time measuring the indentation depth with a sub‐micron resolution. It could be shown that the water uptake of polyamide 6.6 (PA6.6) doubles the indentation depth from approx. 10 microns to approx. 20 microns within the first 2 h. The indentation depth also strongly correlates with the position of measurement on an injection molded plate. Near the gate, the indentation depth measured in processing direction is always higher than at a position far from the gate. Similarly the indentation depth always is higher at the center compared to at the edge of the plate. For amorphous thermoplastics this surface anisotropy can be explained by the molecular orientation resulting from the flow and cooling processes during injection molding. When blending poly(methyl methacrylate) (PMMA) with thermoplastic polyurethane (TPU) the indentation depth increases with increasing TPU content. Overall, scratch testing proves to be a quick and easy tool to investigate surface related effects in plastics engineering and polymer science.

Modeling and validation of the effects of processing parameters on the dimensional stability of an injection-molded polypropylene plate

There has recently been a growing amount of interest in developing process control methods to maintain consistent part quality during injection molding. Some commercially available control methods are believed to offer improved machine and process capability in order to achieve this goal. Regardless of these advantages, however, these methods typically require considerable experimentation before an optimal process setting can be obtained for a particular case. Therefore, a more systematic scheme that does not require extensive experimentation, which in turn costs time and money, is needed. Computer-aided engineering (CAE) is considered to be a good tool for predicting the flow behavior in the cavity during the filling and post-filling stages. If CAE software can accurately predict a part quality indicator, such as one concerned with the dimensional stability, under a given process condition, time-consuming experimentation would no longer be necessary to determine the relationship between the process conditions and part quality. However, the relationship between the process conditions and part quality indicators, such as the dimensional stability, is highly nonlinear and takes no explicit form. The goal of this study is to use CAE tools to establish such a relationship and generate part quality data based on predictions. A second-order regression model is established in order to correlate the part quality with four key process variables using an optimization technique. Finally, we obtain the reference values under these process conditions. A case study was conducted using both a simulation and experimentation for a plaque-shaped piece of polypropylene. The results indicate reasonable agreement between the simulation and experimentation.

About Glassy Amorphous Metal Injection

The paper aims to present studies on the melt flow, melting and rheology of melting in a super-cooled metastable liquid metal, which is injection molded, of the Zr44-Ti11-Cu10-Ni10-Be25 alloy, which can induce selective crystallization. In this process, high Be-velocities were observed, Cu and Ni atoms that crystallized differently in superficial bulk metallic bulk liquids. It wants to highlight and analyze the result of the morphological behavior of microscopic observation regarding Glass Bulk Metallic (BMG) with the composition of a commercial liquid metal alloy (LM001B). One specifies that the injection molded plate was supplied to us by Liquid Metals Technologies Inc., Ca, USA and was manufactured using an Engel injection molding machine operating at 1050-1100°C. The sample that was observed was then cut with a jet of water. FEI Scios Dual-Beam performed microscopic observation. In a cross-section, the presence of crystalline phases can be observed on short-range command. It is also investigated the presence of short-range command groups, their distribution and the effect they can have on the behaviors and properties of alloys. We can now talk about a new material revolution by putting in bulk metallic glasses, Inside Bulk Metallic, (BMGs). It's about metals that are very different from each other, but they can still be combined with the help of intense heat and melted together to produce a beautifully colored and hot liquid. When this liquid is cooled very quickly (fast enough), the metal atoms manage to retain the liquid in a totally random manner, thus forming an amorphous alloy. Glasses made of this amorphous material are very scratch-resistant, BMG material being a plastic, amorphous, but also elastic, but very resistant. You can even speak one of the most powerful materials known today! The weight ratio of BMG can usually be twice as high as that of titanium, magnesium or aluminum. The hardness of the BMG type material is typically a Vickers hardness of more than 500, which is about twice the hardness of most quality stainless steels and titanium and at least four times the hardness of the aluminum and magnesium. BMGs can be three times more elastic or more resistant than virtually all known crystal metal alloys. Some BMGs are highly corrosion-resistant, with alloys containing elements such as beryllium or niobium that tend to be very corrosive. In general, erosion resistance is remarkable in all these BMGs.

Effect of Thickness on Fatigue Crack Propagation in Injection Molded Short Carbon Fiber Reinforced Plastics

The influence of plate thickness on the fatigue crack propagation behavior was studied by using center-notched specimens which were cut from injection-molded plates of short carbon-fiber reinforced polyphenylene sulfide (PPS) at two fiber angles relative to the molding flow direction (MFD), i. e. θ=0 deg. (MD), 90 deg. (TD). The short carbon-fiber reinforced plastics (SCFRP) plates have three-layer structure where the fiber orientation is parallel to MFD in the shell layer and is nearly perpendicular in the core layer. The fraction of the core layer increases with increase in the plate thickness. In the relation between the crack propagation rate,da/dN, and stress intensity factor,ΔK, da/dNincreases with increase in thickness for MD specimen. Conversely,da/dNdecreases for TD specimen. The crack opening displacement along the crack was measured by using the digital image correlation (DIC) method. The measured crack opening displacement become larger with increase in the plate thickness for MD specimens. Contrary, measured values become smaller with increase in the plate thickness for TD specimen. The crack-tip-opening radius,Δρ, was estimated from the parabolic approximation of the crack opening displacement distribution near the crack tip. The relationships betweenda/dNandΔρfor all specimens tend to merge into a unique relationship.

Multi-scale modelling and analysis of strain rate dependent behaviour for long fibre reinforced thermoplastic based on X-ray computed tomography

This paper focuses on the multi-scale modelling method for strain rate dependent behaviour of long fibre reinforced thermoplastics based on the Mori–Tanaka scheme. In the present work, the anisotropic and nonlinear viscoelastic–viscoplastic behaviour of an injection moulded plate are experimentally characterised, and the sensitive range of strain rates is discussed. Fibre orientation tensors, content and fibre length are measured and analysed based on micro computed tomography images at different positions of the plate. Further, a multi-scale material model considering microstructure variables, constitutive models of two phases and failure criteria, is proposed. The accuracy of the model is validated by finite element simulations, including five strain rates and three loading directions. The comparison results indicate that the calculated stress–strain curves show a good consistency with the experimental data.

Effect of copper nanoparticles on the properties of SEBS/PP compounds

This study evaluated the adoption of copper nanoparticles (CuNPs) as an antimicrobial agent in thermoplastic elastomer compounds (TPEs) based on styrene-(ethylene-butylene)-styrene triblock copolymer (SEBS) and polypropylene (PP) for use in the fabrication of automotive air-conditioning systems. The nanocompounds were prepared using a co-rotating double screw extruder and CuNPs were pre-dispersed in polypropylene at weight proportions of 0%, 0.6% and 1.0%. The physical (density), mechanical (tensile and hardness), thermal (differential scanning calorimetry and thermogravimetry) and antimicrobial properties were evaluated on injection molded plates. The antimicrobial properties were evaluated for the bacteria Staphylococcus aureus and Escherichia coli and fungal species commonly found in automotive air conditioners. The results from antibacterial tests showed a reduction of 99.9% in counts of both bacteria tested. There was no fungal growth on the loaded TPE surface. At the tested levels, the addition of CuNPs did not cause significant variations in the TPE properties evaluated.

Anisotropic Elastic-Viscoplastic Properties at Finite Strains of Injection-Moulded Low-Density Polyethylene

Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters.