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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

MODELLING OF ADDITIVE MANUFACTURING – COMPRESSION MOLDING PROCESS USING COMPUTATIONAL FLUID DYNAMICS

A computational fluid dynamics model has been developed to predict the behavior of a printed strands during a novel material extrusion additive manufacturing and compression molding process. While the traditional additive manufacturing process enables control over the fiber orientation within the part, it would also result in high void content. On the other hand, compression molding produces parts with low porosity levels at rapid processing cycle time but lacks control over the microstructure. The novel additive manufacturing – compression molding (AM-CM) integrating both these processes offers control over both the microstructure and porosity to manufacturing high performance composite parts. The numerical model developed here enables to analyze the effect of processing parameters on the behaviour of printed layer that is subsequently compressed and to determine the optimal printing parameters for high-performance composite part design.

Seta, Berin↗
DOE OSTI2022

Long fiber injection molding

An improved method for obtaining high fiber volume fraction, long fiber injection molded articles is provided. According to one embodiment, the method includes forming an injection molding feedstock by cutting pre-impregnated fiber-reinforced tape into platelets. The platelets can be coated with a thin layer of polymer to allow sliding of the platelets with respect to each other at the early stages of plastication, rather than forcing relative motion of fibers with respect to each other. The method can further include the dispersion of material only in the final stages of the injection molding screw to promote gentle motion of the feedstock at the earlier stages of the plastication process. The method allows improvement of mechanical properties of articles manufactured with equipment and techniques that are prevalent in high volume automotive and consumer industries.

Kunc, Vlastimil↗
DOE OSTI2023

Process Variability Effects on Tensile Response in Injection Molded, Fluorinated Thermoplastics

The mechanical properties of fluorinated thermoplastics (i.e., tensile strength and elongation) can vary with changes in injection molding processing parameters. Four fluoropolymers are examined: poly(vinylidene fluoride) (PVDF) and random poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) with three CTFE concentrations. Dog bones were manufactured with various cylinder dwell times and mold cooling times to assess the manufacturing sensitivity to the tensile response. Dwell and cooling times increasingly impact mechanical performance as CTFE concentration increases. Specimens exhibit higher tensile strength as a function of injection order. The first injected specimen exhibits the lowest tensile strength and highest elongation in all copolymers. This trend becomes more pronounced among fluoropolymers with higher CTFE concentration and lower weight-averaged molecular weight. Parallel plate rheology was used to obtain the zero-shear viscosity as a function of material type, process, and injection order. We found that in the copolymers, the first injected sample exhibited a lower zero-shear viscosity than the next, which indicates a lower molecular weight in the first injected specimen. This phenomenon was not presented for the PVDF homopolymer. Copolymer mechanical uncertainties are hypothesized to result from the shorter molecular weight chains extruding out of the specimens' sides as a flash due to higher mobility with CTFE segments.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Reliability in the characterization of fiber length distributions of injection molded long carbon fiber composites

The mechanical properties of a discontinuous fiber reinforced composite material are dependent on the length of the reinforcing fibers. Long-fiber thermoplastic (LFT) composites offer a compromise between ease of manufacture and mechanical properties for structural applications and are conventionally made using fibers that are initially 10–14 mm long. However, fiber attrition during the injection molding process significantly reduces the final fiber lengths in molded composite and produces a fiber length distribution (FLD), which depends on the processing parameters. Thus, accurate FLD measurements are important for reliable predictions of the composite properties. Here, we present a detailed methodology for experimentally measuring the FLD in LFT composites based on best practices. Possible biases occurring during the measurement process are discussed and their effect on the measured FLD and averaged fiber length values are evaluated. We then employ a Mori–Tanaka implementation of the Eshelby model to predict the elastic stiffness of the LFT composite and analyze the sensitivity of the stiffness values to the biases in the FLD measurements.

long-fiber thermoplastics, injection molding, fibe↗
DOE OSTI2019

Reinforcement of Soy Protein-Based Bioplastics Through Addition of Lignocellulose and Injection Molding Processing Conditions

Bioplastics have gained great interest in recent years as a potential alternative to conventional plastics, since they are renewable and biodegradable materials. However, their mechanical properties are not able to match those of conventional plastics yet. In this context, the incorporation of additives to improve those properties of bioplastics is an interesting line of research. The aim of this work was to develop soy protein-based bioplastics with lignocellulosic fiber (additive) by injection molding. Mechanical and absorption properties of bioplastics reinforced with lignocellulose (0.1, 1.0, 5.0 wt%) have been studied, as well as their microstructure. Furthermore, a study of the effect produced by changing the mold temperature (70, 90, 110, 130 °C) was carried out. The results obtained confirm an improvement of the mechanical properties of these bioplastics, depending on the amount of fiber incorporated. In any case, these findings support the role of cellulosic compounds as additives in protein bioplastics.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Analysis of Mold Friction in a Continuous Casting Using Wavelet Transform

Mold friction (MDF) is an important parameter reflecting the lubrication condition between the initial shell and the mold during continuous casting. In this article, based on practical MDF from the slab continuous casting driven by a mechanical vibration device, the characteristics of friction were analyzed by continuous wavelet transform (CWT) and discrete wavelet transform (DWT) in different casting conditions, such as normal casting, level fluctuation, and alarming of the temperature measurement system. The results show that the CWT of friction accurately captures the subtle changes in friction force, such as the periodic characteristic of MDF during normal casting and the disordered feature of MDF during level fluctuation. Most important, the results capture the occurrence of abnormal casting and display the friction frequency characteristics at this abnormal time. In addition, in this article, there are some abnormal casting conditions, and the friction signal is stable until there is a sudden large change when abnormal casting, such as split breakout and submerged entry nozzle breakage, occurs. The DWT has a good ability to capture the friction characteristics for such abnormal situations. In particular, the potential abnormal features of MDF were presented in advance, which provides strong support for identifying abnormal casting and even preventing abnormal casting.

42 ENGINEERING↗
DOE OSTI2019

Characterization of Roughness, Porosity and Thermal Resistances of Continuous Casting Mold Slag Layers Devitrified and Crystallized in Laboratory

This paper presents an experimental investigation about the variation, with temperature, of surface roughness, porosity, degree of crystallization and microstructure, occurring in solid layers of a commercial mold powder slag used for casting medium carbon steel thin slabs. Characterization is done with samples devitrified and crystallized at 698 K, 823 K, 898 K and 973 K (425 °C, 550 °C, 625 °C and 700 °C) for 10,800 seconds, in the furnace of a high-temperature confocal laser scanning microscope. As well as, with slag disks devitrified non-isothermally in a heat flow apparatus based on the application of Fourier's law in steady state conditions, where the high temperature surface is maintained at selected values, between 927 K and 1241 K (654 °C and 968 °C). Surface roughness and porosity determinations are performed by image analysis of confocal laser scanning and scanning electron micrographs, respectively. For the time considered and temperatures ≥ 823 K (550 °C) the slag crystallizes completely, and variations of roughness and porosity with temperature are associated with changes in size and packing of the primary crystalline-phase grains. Crystallization induced porosity is significant and causes slag layer expansion. Hence crystallization does not lead to gap formation with a neighboring surface (e.g., mold wall) by shrinkage. Instead, surface separation arises from development of roughness, and measurements with the heat flow apparatus confirm that interfacial thermal resistance between a slag layer and a metallic wall can be estimated from the sum of the means of maximum peak to valley height of their surfaces. Furthermore, the results establish that slag layers roughness and porosity increase with temperature and reveal effective thermal conductivities in the range of ~ 0.3 to ~ 0.5 W/m K. Low effective thermal conductivities must be a consequence of porous bands, whose porosity depends on temperature and reaches values as high as ~ 0.20 and ~ 0.50.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Material extrusion with integrated compression molding of NdFeB/SmFeN nylon bonded magnets using small- and large-scale pellet-based 3D-printers

High-density bonded rare-earth magnets are manufactured using pellet-fed additive manufacturing (AM)/material extrusion and an integrated additive manufacturing-compression molding (AM-CM) process. Neodymium iron boron – samarium iron nitride in polyamide 12 (NdFeB-SmFeN/PA12) of 93 % weight fraction (65 % volume fraction) are used for the study. The mechanical properties (tensile strength and modulus), magnetic properties (maximum energy density, coercivity, remanence) are reported. Manufacturing parameters such as layer height, barrel temperatures, screw speed and gantry feed rate are optimized to obtain the highest possible density of the magnets using a small-scale desktop material extrusion printer. Large scale integrated additive manufacturing-compression molding (AM-CM) is then utilized to increase the density of the magnets by reducing porosity defects common in the material extrusion process. The density of as-printed magnets was 5.2 g/cm 3 with a BH max value of 124.14 kJ/m 3 , tensile strength of 20 MPa and a modulus of 2 GPa. AM-CM increased the density of the compound by 5.5 % (5.49 g/cm 3 ). The reduction in porosity was confirmed using X-ray tomography (XCT). Improvement in mechanical strength of the material was also observed, with an increase in tensile strength of 25 % (25.09 MPa) and increase in tensile modulus of 275 % (5.49 GPa). Scanning electron microscopy showed increased particle-matrix adhesion with the integrated AM-CM process.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Numerical framework for integrated additive manufacturing-compression molding (AM-CM) of thermoplastic composites

Additive manufacturing-compression molding (AM-CM) has emerged as a transformative technology in advanced composite manufacturing. Additive manufacturing (AM) offers high design flexibility and the ability to produce complex geometries with precisely aligned fibers in the preferred orientation. Compression molding (CM) enhances composite materials by providing excellent dimensional stability, reduced porosity, high production rates, and a smooth surface finish. Despite these advantages, extensive integrated analysis is required to optimize processing conditions for improved fiber orientation distribution (FOD) and porosity control. Here, this study develops a comprehensive numerical model to simulate the AM-CM manufacturing process. The model isolates the effects of both the AM and CM phases while also capturing their integration. Additionally, it accounts for heat transfer, temperature-dependent viscosity, and fiber orientation in the extruded fiber-filled polymer, accurately representing material behavior during processing. This approach enables the analysis of interactions between deposited beads of complex strand shapes and their interface regions after full compression. Moreover, the model predicts key parameters such as polymer flowability, fiber orientation, and temperature evolution in AM-CM parts. By optimizing processing conditions, it facilitates a controlled and predictable microstructure.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Simulation-driven design optimization of reaction injection molding (RIM) process for polydicyclopentadiene (pDCPD): Minimizing cycle time, defects, and warpage

Replacing metal components in trucks, trailers, and buses with lightweight polymer composites is challenging due to high temperatures and complex manufacturing. The Reaction Injection Molding (RIM) process using Dicyclopentadiene (DCPD) resin offers a solution by producing robust parts with excellent stiffness, impact strength, and resistance properties. Simulations are essential for optimizing this process, predicting defects, and improving quality. However, most commercial software is tailored for thermoplastics, requiring thermoset users to generate their own datasets. In this study, a material data card for DCPD was developed to perform RIM simulations. Design of Experiments (DOE) was used to identify key factors affecting filling, curing, and warpage, aiming to minimize cycle time and defects. The simulations explored varying injection gate parameters (size, location, number) and process conditions (mold/resin temperature, injection/curing pressure). Results showed that gate design significantly impacts filling behavior and defects. A single central gate provided balanced flow with fewer defects, while two corner gates led to more defects. Additionally, lower injection pressure increased filling time, while higher mold temperature accelerated curing but led to more warpage. In conclusion, this optimization framework aims to enhance DCPD part performance and promote sustainable manufacturing by reducing waste and energy consumption.

42 ENGINEERING↗
DOE OSTI2022

A level set approach for the computational study of a yield stress fluid filling a thin mold

Many important engineering and scientific applications such as cement slurries, foams, crude oil, and granular avalanches involve the concept of yield stress. Therefore, modeling yield stress fluids in different flow configurations, including the accurate prediction of the yield surface, is important. In this paper, we present a computational model based on the finite element method to study the flow of yield stress fluids in a thin mold and compare the results with data from flow visualization experiments. Here, we use the level set method to describe the interface between the filling fluid and air. We use polypropylene glycol as a model Newtonian fluid and Carbopol for the model yield stress fluid, as the Carbopol solution demonstrates yielding without thixotropy. To describe the yielding and shear-thinning behavior, we use a generalized Newtonian constitutive equation with a Bingham–Carreau–Yasuda form. We compare the results obtained from the mold filling experiments with the results from the three-dimensional (3D) model and from a reduced-order Hele-Shaw (HS) model that is two-dimensional, including the effect of shear-thinning along the thin direction only approximately. We show that both the 3D and the HS model can capture the experimental meniscus shape reasonably well for all the fluids considered at three different flow rates. This indicates that the shape evolution is insensitive to the dimensionality of the model. However, the viscosity and yield surfaces predicted by the 3D and HS models are different. The HS model underestimates the high viscosity and unyielded regions compared to the estimation by the 3D model.

42 ENGINEERING↗
DOE OSTI2021

Compression molding of anisotropic NdFeB bonded magnets in a polycarbonate matrix

Anisotropic bonded Nd 2 Fe 14 B (NdFeB) magnets in a polycarbonate (PC) binder matrix are fabricated using a compression molding process. The weight fractions (w.f.) of NdFeB in PC on the batch mixer are 20, 50, 75, 85 and 95% compared to the twin screw extruder with 20, 50 and 75% respectively. The density of the 95% batch mixed magnets fabricated was 5.34 g/cm 3 and the magnetic properties are, intrinsic coercivity H ci = 942.99 kA/m, remanence B r = 0.86 T, and energy product (BH) max = 120.96 kJ/m 3 . Furthermore, the measured tensile properties are in the range of 27-59 MPa, comparable to that of polyamide (PA), polyphenylene sulfide (PPS) bonded magnets and demonstrating potential for bonded magnet applications. Scanning electron microscopy showed that the onset of failure occurs in the magnetic particle- matrix interface. This study demonstrates that compression additive molding technique can be used to fabricate high performance NdFeB polycarbonate composite magnets with improved mechanical properties.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Wall-slip of highly filled powder injection molding compounds: Effect of flow channel geometry and roughness

The paper deals with the rheological behavior of highly filled compounds proceeded via powder injection molding (PIM) and applied in many sectors of industry (automotive, medicine, electronic or military). Online rheometer equipped with slit dies varying in surface roughness and dimensions was applied to investigate the wall-slip as a rheological phenomenon, which can be considered as a parameter indicating the separation of compound components (polymer binder and metallic powder) during high shear rates when injection molded.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Simulative design and process optimization of the two-stage stretch-blow molding process

The total production costs of PET bottles are significantly affected by the costs of raw material. Approximately 70 % of the total costs are spent for the raw material. Therefore, stretch-blow molding industry intends to reduce the total production costs by an optimized material efficiency. However, there is often a trade-off between an optimized material efficiency and required product properties. Due to a multitude of complex boundary conditions, the design process of new stretch-blow molded products is still a challenging task and is often based on empirical knowledge. Application of current CAE-tools supports the design process by reducing development time and costs. This paper describes an approach to determine optimized preform geometry and corresponding process parameters iteratively. The wall thickness distribution and the local stretch ratios of the blown bottle are calculated in 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. Taking into account the correlation between material usage, process history and resulting product properties, integrative coupled simulation steps, e.g. structural analyses or barrier simulations, are performed. The approach is applied on a 0.5 liter PET bottle of Krones AG, Neutraubling, Germany. The investigations point out that the design process can be supported by applying this simulative optimization approach. In an optimization study the total bottle weight is reduced from 18.5 g to 15.5 g. The validation of the computed results is in progress.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Predictive Engineering Tools for Injection-Molded Long-Carbon-Fiber Thermoplastic Composites - FY 2014 First Quarterly Report

The CRADA between PNNL, Autodesk, Toyota and Magna has been effective since October 28th, 2013. The whole team including CRADA and subcontract partners kicked off the project technically on November 1st, 2013. This report describes work performed during the first quarter of FY 2014. The following technical progresses have been made toward project milestones: 1) The project kickoff meeting was organized at PlastiComp, Inc. in Winona on November 13th, 2013 involving all the project partners. During this meeting the research plan and Gantt chart were discussed and refined. The coordination of the research activities among the partners was also discussed to ensure that the deliverables and timeline will be met. 2) Autodesk delivered a research version of ASMI to PNNL for process modeling using this tool under the project. PNNL installed this research version on a PNNL computer and tested it. Currently, PNNL is using ASMI to prepare the models for PlastiComp plaques. 3) PlastiComp has compounded long carbon-fiber reinforced polypropylene and polyamide 6,6 compounds for rheological and thermal characterization tests by the Autodesk laboratories in Melbourne, Australia. 4) Initial mold flow analysis was carried out by PlastiComp to confirm that the 3D complex part selected by Toyota as a representative automotive part is moldable. 5) Toyota, Magna, PlastiComp and PNNL finalized the planning for molding the Toyota 3D complex part. 6) Purdue University worked with PNNL to update and specify the test matrix for characterization of fiber length/orientation. 7) Purdue University developed tools to automate the data collection and analysis of fiber length and orientation measurements. 8) Purdue University designed and specified equipment to replace the need for equipment using the technology established by the University of Leeds at General Motors.

42 ENGINEERING↗
DOE OSTI2023

Process Variability Effects on Tensile Response in Injection Molded, Fluorinated Thermoplastics

The mechanical properties of fluorinated thermoplastics (i.e., tensile strength and elongation) can vary with changes in injection molding processing parameters. Four fluoropolymers are examined: poly(vinylidene fluoride) (PVDF) and random poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) with three CTFE concentrations. Dog bones were manufactured with various cylinder dwell times and mold cooling times to assess the manufacturing sensitivity to the tensile response. Dwell and cooling times increasingly impact mechanical performance as CTFE concentration increases. Specimens exhibit higher tensile strength as a function of injection order. The first injected specimen exhibits the lowest tensile strength and highest elongation in all copolymers. This trend becomes more pronounced among fluoropolymers with higher CTFE concentration and lower weight-averaged molecular weight. Parallel plate rheology was used to obtain the zero-shear viscosity as a function of material type, process, and injection order. We found that in the copolymers, the first injected sample exhibited a lower zero-shear viscosity than the next, which indicates a lower molecular weight in the first injected specimen. This phenomenon was not present for the PVDF homopolymer. Copolymer mechanical uncertainties are hypothesized to result from the shorter molecular weight chains extruding out of the specimens’ sides as a flash due to higher mobility with CTFE segments.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Avirulent Isolates of Penicillium chrysogenum to Control the Blue Mold of Apple Caused by P. expansum

Blue mold is an economically significant postharvest disease of pome fruit that is primarily caused by Penicillium expansum. To manage this disease and sustain product quality, novel decay intervention strategies are needed that also maintain long-term efficacy. Biocontrol organisms and natural products are promising tools for managing postharvest diseases. Here, two Penicillium chrysogenum isolates, 404 and 413, were investigated as potential biocontrol agents against P. expansum in apple. Notably, 404 and 413 were non-pathogenic in apple, yet they grew vigorously in vitro when compared to the highly aggressive P. expansum R19 and Pe21 isolates. Whole-genome sequencing and species-specific barcoding identified both strains as P. chrysogenum. Each P. chrysogenum strain was inoculated in apple with the subsequent co-inoculation of R19 or Pe21 simultaneously, 3, or 7 days after prior inoculation with 404 or 413. The co-inoculation of these isolates showed reduced decay incidence and severity, with the most significant reduction from the longer establishment of P. chrysogenum. In vitro growth showed no antagonism between species, further suggesting competitive niche colonization as the mode of action for decay reduction. Both P. chrysogenum isolates had incomplete patulin gene clusters but tolerated patulin treatment. Finally, hygromycin resistance was observed for both P. chrysogenum isolates, yet they are not multiresistant to apple postharvest fungicides. Overall, we demonstrate the translative potential of P. chrysogenum to serve as an effective biocontrol agent against blue mold decay in apples, pending practical optimization and formulation.

59 BASIC BIOLOGICAL SCIENCES↗