Polymer Parts Research Articles

Prediction of micro wear depth between engineering polymers

In the polymer industry, changes in the wear area that affect surface aesthetics have emerged as a significant issue in applications where surface appearance is crucial. Even minute changes in surface height can be visible to the naked eye, necessitating the need for micro-scale wear prediction of polymers. While the Archard model has been verified for decades for metal-metal or polymer-metal contact, predicting wear between polymer-polymer contacts remains challenging due to limitations in wear measurement and wear coefficient determination. In this study, we propose a method for determining the wear coefficient for polymer-polymer contact and validate the prediction model with a component wear test on polymer parts. Wear depth, an essential indicator of wear is measured after the sliding wear test of the polycarbonate (PC) pin and Acrylonitrile butadiene styrene (ABS) copolymer plate. The wear prediction model with the obtained wear coefficient exhibits 99.7 % accuracy in comparison to the test wear depth. A component wear test is performed on engineering polymer parts, and wear prediction under test conditions is made using the proposed model. The measured and predicted wear depth of the component demonstrates a difference smaller than 5 μm, which is within the range of no change in scratch visibility. This study ensures the accurate wear prediction of engineering polymer components with affordable computational efficiency. The ability to predict polymer-polymer wear, previously unattainable, will enable several applications in the polymer industry, such as component design, scratch visibility prediction, and quality assurance.

Digital Light Processing to Afford High Resolution and Degradable CO2‐Derived Copolymer Elastomers

AbstractVat photopolymerization 3D printing has proven very successful for the rapid additive manufacturing (AM) of polymeric parts at high resolution. However, the range of materials that can be printed and their resulting properties remains narrow. Herein, we report the successful AM of a series of poly(carbonate‐b‐ester‐b‐carbonate) elastomers, derived from carbon dioxide and bio‐derived ϵ‐decalactone. By employing a highly active and selective Co(II)Mg(II) polymerization catalyst, an ABA triblock copolymer (Mn=6.3 kg mol−1, ÐM=1.26) was synthesized, formulated into resins which were 3D printed using digital light processing (DLP) and a thiol‐ene‐based crosslinking system. A series of elastomeric and degradable thermosets were produced, with varying thiol cross‐linker length and poly(ethylene glycol) content, to produce complex triply periodic geometries at high resolution. Thermomechanical characterization of the materials reveals printing‐induced microphase separation and tunable hydrophilicity. These findings highlight how utilizing DLP can produce sustainable materials from low molar mass polyols quickly and at high resolution. The 3D printing of these functional materials may help to expedite the production of sustainable plastics and elastomers with potential to replace conventional petrochemical‐based options.

Digital Light Processing to Afford High Resolution and Degradable CO2-Derived Copolymer Elastomers.

Vat photopolymerization 3D printing has proven very successful for the rapid additive manufacturing (AM) of polymeric parts at high resolution. However, the range of materials that can be printed and their resulting properties remains narrow. Herein, we report the successful AM of a series of poly(carbonate-b-ester-b-carbonate) elastomers, derived from carbon dioxide and bio-derived ϵ-decalactone. By employing a highly active and selective Co(II)Mg(II) polymerization catalyst, an ABA triblock copolymer (Mn=6.3 kg mol-1, ÐM=1.26) was synthesized, formulated into resins which were 3D printed using digital light processing (DLP) and a thiol-ene-based crosslinking system. A series of elastomeric and degradable thermosets were produced, with varying thiol cross-linker length and poly(ethylene glycol) content, to produce complex triply periodic geometries at high resolution. Thermomechanical characterization of the materials reveals printing-induced microphase separation and tunable hydrophilicity. These findings highlight how utilizing DLP can produce sustainable materials from low molar mass polyols quickly and at high resolution. The 3D printing of these functional materials may help to expedite the production of sustainable plastics and elastomers with potential to replace conventional petrochemical-based options.

Electroplating Additively Manufactured Honeycomb Structures to Increase Energy Absorption Under Quasi-Static Crush

Honeycomb (HC) has been used in energy absorption applications due to its high stiffness and low density. Metallic HC are used for energy absorption applications, however, these metallic structures can be challenging to manufacture if complex geometric features designed to improve energy absorption are used, which motivates the use of additive manufacturing (AM). Metal AM methods include powder bed fusion (PBF) and direct energy deposition (DED). In addition to capital equipment cost, these processes possess challenges that include a required inert environment, powder handling, final part porosity, residual stresses, and nonuniform surface finish. These concerns can be alleviated through the use of polymer AM, however, polymeric parts exhibit brittle failure and have a lower stiffness than metallic HC structures. In this study, a low-cost 3D polymer printing method, stereolithography (SLA), is combined with a conventional electroplating process to fabricate a metal-plastic composite HC structure with energy absorption capability much greater than of a plastic HC structures of the same nominal volume. SLA parts have a smooth surface, so that the surface finish is at least as uniform after electroplating as the SLA part. The energy absorption characteristics of the electroplated HC is studied to determine how these energy absorbing materials can be manufactured at reduced cost. Our study confirms that the metal-plastic composite HC increases both the crush strain range and the mean crush stress of these samples, resulting in metal-plastic composite HC structures with substantially increased energy absorption. This study also examines how buckling initiators (BIs), or diamond shaped holes located at 50, 75, and 100% of the height of the hexagonal cell vertices, can influence energy absorption performance. This study shows that it is feasible to fabricate electroplated HCs, using an SLA preform, to achieve a substantial increase in energy absorption over using SLA alone.

Numerical analysis of the effects of pores on propagating guided waves

The present numerical study aims to analyze the effect of pores on propagating guided waves while outlining the relevance of pore formation and its significance to structural properties. The primary focus of this study was on the pores present in planar carbon fiber-reinforced polymer (CFRP) parts. The wavefield data were generated by applying the elastodynamic finite integration technique (EFIT) solver AE3D, allowing for a systematic analysis based on fully controllable configurations and noise-free data. An isotropic material model was used to simplify the modeling of the anisotropic CFRP by assuming the averaged quasi-isotropic properties of the CFRP in all directions. More than 220 specimens containing single pores or four basic configurations of pore accumulations were modeled and analyzed in terms of their effect on the out-of-plane component of the propagating guided waves. Analysis of the guided wavefield data focused on the direction-dependent maximum amplitude differences and deviations in the wavefield energy. Mode- and wavenumber-specific amplitude loss along the centerline was analyzed using a matrix pencil algorithm. Finally, principal component analysis (PCA) was conducted to examine deviations caused by the presence of pores. Analysis of the wavefield effects of the pores for each specific configuration showed good differentiation between the considered pore volume groups. At the same time, the effects of the pores were shown to be significantly dependent on the pore configuration in terms of orientation and morphological properties. Associated with this, the intersecting outcome ranges for different pore volume groups were evident when all the pore configurations were considered simultaneously.

Adsorption characteristics of Janus tadpole polymers

The shape of Janus particles is directly connected to their adsorption behavior. Janus tadpole polymers offer a unique topological architecture that includes competition between entropic, enthalpic, and topological terms in the adsorption free energy; accordingly, non-trivial adsorption behavior patterns are expected. We study the surface adsorption of Janus tadpole polymers by means of Monte Carlo simulations, finding that, depending on which part of the tadpole polymers is preferentially adsorbing on the surface, very different types of behavior for both the adsorbed polymeric phase and of the brush arise. The adsorbed phase and the brush mutually influence each other, leading to a variety of phenomena such as nematic ordering of the adsorbed stiff tadpole tails and intriguing changes in the territoriality of adsorbed ring polymers on the surface. We analyze in detail our findings, revealing the mechanisms behind the organization and ordering, and opening up new possibilities to tune and control the structure of such systems.

The importance of print orientation in numerical modelling of 3D printed structures under impact loading

Anisotropy is commonly observed in 3D-printed polymer and composite parts, particularly when manufactured by fused filament fabrication (FFF). This anisotropy can lead to difficulty obtaining accurate material properties during mechanical characterisation. This study establishes a connection between the print parameters used in specimen characterisation and their influence on the accuracy of numerical models for 3D-printed cellular structures under impact. Material properties from only one of the characterisation variants studied, with a parallel infill, accurately represented the force response and physical damage of the experimental samples. In contrast, the default characterisation specimen with a ±45° infill underpredicted the peak force and overpredicted the impact duration, potentially leading to underestimating impact severity. This discrepancy could result in greater damage to a person or structure being protected. It is recommended that the parallel infill pattern be used when characterising materials for use in FFF cellular structures under impact loading to ensure more reliable simulations and improved design of impact-resistant structures.

Quantitative correlation between temperature difference and sintering neck length in material extrusion-based additive manufacturing

The performance of polymeric parts fabricated via material extrusion-based additive manufacturing (MEAM) is significantly influenced by the sintering neck length between filaments. Despite its importance, elucidating the underlying mechanism governing the formation of inter-filament sintering necks is challenging due to the difficulties in monitoring temperature fields during MEAM. In this work, the thermal condition in MEAM was simplified using a printer with a tubular hotbed, coupled with a high temporal-spatial resolution infrared (IR) camera to monitor temperature field variations during printing. An advanced IR image processing method, integrating multi-directional retrieval and whole-loop average filtering, was developed to accurately measure temperature differences between filaments. By correlating these measurements with micro-CT characterizations, a quantitative relationship between temperature difference and sintering neck length was established. Through single- or multi-loop defect experiments, microscopic defect detection and analysis were conducted, achieving the prediction of sintering neck length variations at a 10 μm level with an 85 % accuracy. This work is believed to provide potential value for further accurate prediction of the mechanical properties of MEAM parts.

Investigation on FDM process parameters for the dimensional accuracy with ABS polymer part

The accuracy of manufactured parts holds paramount importance in product assembly. Among various additive manufacturing (AM) techniques, fused deposition modeling (FDM) stands out for its emphasis on accuracy, surface quality, and precision. Hitherto, some investigations have been conducted on dimensional accuracy which are limited to few geometrical shapes and remains inadequately explored. This study adopts an experimental approach to investigate the influence of FDM printing parameters including build orientation (BO), layer thickness (LT), and infill density (ID) on the dimensional accuracy of ABS polymer printed benchmark. Taguchi’s L9 orthogonal array is utilized to assess the correlation between the chosen FDM process parameters and the obtained responses. Measurements of deviations of the printed parts are conducted using a vision measuring machine (VMM) and analyzed employing the ‘nominal-is-the-best’ method. In this study, the most influencing parameter is changing as the geometrical shapes vary. Analysis of variance (ANOVA) is performed to examine the adequacy of the model, considering p-values less than 0.05 at 95% confidence level. The model is found adequate for all the dimensions of the benchmark. The study concludes that the parameter setting will vary with the changes in features. This study will pave the way in selecting the process parameters to get the desired dimensional accuracy for improving the quality of critical applications like prototyping and functional end-use manufacturing.

Generative design of conformal cooling channels for hybrid-manufactured injection moulding tools

Effective cooling systems for injection moulding (IM) tools are critical to reducing manufacturing costs and cycle time for the polymer parts produced. This work presents a novel automated methodology for designing conformal cooling channels (CCCs) for IM tools via interlinking commercial moulding simulation tools with custom scripts. These scripts adjust CCC design in response to the spatial variability in global and local temperatures at the mould tool-part interface (MTPI) via generative design (GD). Four tool designs for manufacturing a simplified part were analysed numerically simulation and experimentally, including tools with either straight-drilled (non-conformal) cooling channels (tool steel), a manually designed CCC system (stainless steel or bronze alloy), or an automatically designed CCC system (stainless steel). While both manually designed CCC tools cool the part faster than the non-conformal tool (3–5% predicted vs. 40% measured for stainless steel and 9–12% predicted vs. 40% measured for bronze alloy), the GD-optimised CCC tool outperformed both (15–30% predicted faster cooling vs. 70% measured). The predicted MTPI temperature feature achieves reductions to both maximum and spatial variability in MTPI temperatures, which lead directly to significant reductions in manufacturing cycle time and polymer part warpage. These findings could have a major impact on the IM industry by reducing tool design costs and raw material waste via improving moulded part quality.

Feasibility study of friction stir joining of aluminium with carbon fibre reinforced thermoplastic composite

During the last decades, environmental concerns and limited resources have set focus of research on lightweight, mechanically high-performing structures for the transportation industry, in order to reduce fuel consumptions and CO2 emissions. Friction Stir Joining (FSJ), as a variant of the Friction Stir Welding (FSW), is an innovative friction-based joining technique for metal-composite hybrid structures. Joining in the plasticized state below the melting temperature of the metal leads to a comparatively small heat-affected zone, so that only minor metallurgical changes occur. Additionally, only a short processing time and no additional weight in form of fasteners is needed. The main objective of this study is to evaluate the feasibility of metal-composite structures via FSJ, intending to enable a macro-mechanical interlocking bonding mechanism. Main focus was given to the integration of an aluminium nub inserted in a carbon fiber-reinforced polyphenylene sulfide (CF-PPS) sheet, to ensure sufficient plasticization of the aluminium part and no degradation in the polymer part. Residual stress arising from the friction stir joining process was also characterised using the Contour method. In this study, aluminium alloy 6082-T6 and CF-PPS composite sheets were used to produce long lap joints. Results have shown that the joints were created at almost constant peak temperature slightly above the melting temperature of the PPS but no physical-chemical changes were detected in the PPS. In addition, the influence of a PPS film as interlayer between the sheets was investigated in order to explore a method for preventing galvanic corrosion. Preliminary results indicate that it is not possible to integrate a metal nub to the CF-PPS without interrupting the PPS film. However, it is possible to create a nub within the PPS film.

Lattice optimization of fiber-reinforced polymer parts fabricated by additive manufacturing: the impact of Bezier curve order on mechanical properties

PurposeLattice structures are widely used for achieving optimal topology in additive manufacturing. However, the use of different lattices in a single design can result in stress concentrations at the transition points. This study aims to investigate the influence of Bezier curves on mechanical properties during the transformation from one lattice structure to another. It specifically focuses on the transition from a hexagonal to diamond lattice, using Bezier curves of various orders.Design/methodology/approachThe curves were designed by passing them through the same control points for different orders, such as third, fifth and seventh. The samples were sliced for 3D printing, and a tensile test was conducted. Young’s modulus and energy absorption abilities were measured to compare the mechanical properties of the models created with Bezier curves for the transformation between hexagonal and diamond models.FindingsThe analysis revealed a gradual change in mechanical properties from the hexagonal to the diamond lattice. Moreover, different orders of Bezier curves exhibited varying mechanical properties during the transformation between the two lattices. As the order of the Bezier curve increased, the mechanical properties smoothly changed from the hexagonal to diamond lattice. This prevented stress concentrations or mechanical behavior mismatch caused by sudden deformations at the transitions between the curves used in the design.Originality/valueThe study’s innovative use of Bezier curves of different orders to smoothly transformation between hexagonal and diamond lattices in additive manufacturing offers a practical solution to prevent stress concentrations and mechanical inconsistencies during such design transitions.

Tensile, flexural and fracture properties of MEX-printed PLA-based composites

Due to the continuous development of material extrusion-additive manufacturing (MEX-AM) technology, the fracture behavior of polymeric parts, and especially of their associated composites, presents some shortcomings and also a challenge in the field. In this paper, the fracture properties of non-reinforced (NR) and reinforced Polylactic Acid (PLA) samples manufactured by MEX-AM process are investigated through tensile, flexural and fracture mechanics tests. The samples are reinforced with glass fibers (GF-PLA), carbon fibers (CF-PLA) and bronze particles (BP-PLA), and tested parallel (named FLAT for all tests) and normal (named UPRIGHT for tensile test, and ON-EDGE for flexural and fracture mechanics tests) to the layer growth (LG). It was found that regardless of the type of test, the LG and the material significantly influence the mechanical properties and collapse modes of the MEX-printed samples. It was obtained that the parallel-LG load is favorable for the tensile and flexural tests, and the normal-LG for the fracture mechanics tests. Overall, the NR-PLA material gives the best strength, strain and energy absorption properties, CF-PLA stands out as the stiffest material, while BP-PLA presents the minimum performances for almost all properties. The macroscopic analyzes of the fractured samples clearly highlight distinct failure mechanisms associated with each type of test, material and LG. From the analysis of the mechanical behavior and macrostructural images, CF-PLA was identified as the most brittle material, and NR-PLA the most ductile.

Warpage detection in 3D printing of polymer parts: a deep learning approach

Warpage detection in 3D printing of polymer parts: a deep learning approach

Exploring expected values of topological indices of random cyclodecane chains for chemical insights

Chemical graph theory has made a significant contribution to understand the chemical compound properties in the modern era of chemical science. At present, calculation of the topological indices is one of most important area of research in the field of chemical graph theory. Cyclodecane is a cyclic hydrocarbon with the chemical formula C10H20\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$C_{10}H_{20}$$\\end{document}. It consists of a ring of ten carbon atoms bonded together in a cyclical structure. Cyclodecane chains can be part of larger molecules or polymers, where multiple cyclodecane rings are connected together. These molecules can have various applications in chemistry, materials science, and pharmaceuticals. This article aims to determine expected values of some connectivity based topological indices of random cyclodecane chains, containing saturated hydrocarbons with at least two rings. It also compares these descriptors using explicit formulae, numerical tables and present graphical profiles of these comparisons.

Numerical and experimental investigation of direct rapid tooling for sheet metal forming using selective laser sintering

The rapid tooling approaches were most sought after for the low-volume production of sheet metal parts within a short duration. This study presents an investigation of direct rapid tools produced with Selective Laser Sintering (SLS) for sheet metal forming. SLS is one of the widely used additive manufacturing techniques to produce polymer parts. The ability to form the sheet metal components using SLS direct rapid tools was assessed through cup drawing from aluminium blanks. A full factorial experiment was formulated to design the tools by varying the punch radius, die radius and draw ratio. The tools were fabricated with SLS using glass bead - filled polyamide material (PAGF) and finite element analysis was employed to study the stress distribution. The stress concentrations were observed at the tool edge radius, yet the PAGF tools sustained the load from the cup drawing process. The inspection of the PAGF tools and drawn cups shows that they are sensitive to the edge radius and draw ratio. Wear at the edge radius was evaluated in terms of percentage deviation from the initial radius. While the designed dimension of the edge radius is a significant factor affecting respective tool edges, the die edge wear was also influenced by the draw ratio. Both the formed parts and the tools exhibit geometrical variations localised to the forming edges and demonstrate good repeatability even up to 200 draw cycles.

Quantitative Insight into the Compressive Strain Rate Sensitivity of Polylactic Acid, Acrylonitrile Butadiene Styrene, Polyamide 12, and Polypropylene in Material Extrusion Additive Manufacturing

Herein, a research and engineering gap, i.e., the quantitative determination of the effects of the compressive loading rate on the engineering response of the most popular polymers in Material Extrusion (MEX) Additive Manufacturing (AM) is successfully filled out. PLA (Polylactic Acid), ABS (Acrylonitrile Butadiene Styrene), PP (Polypropylene), and PA12 (Polyamide 12) raw powders were evaluated and melt-extruded to produce fully documented filaments for 3D printing. Compressive specimens after the ASTM-D695 standard were then fabricated with MEX AM. The compressive tests were carried out in pure quasi-static conditions of the test standard (1.3 mm/min) and in accelerated loading rates of 50, 100, 150, and 200 mm/min respectively per polymer. The experimental and evaluation course proved differences in engineering responses among different polymers, in terms of compressive strength, elasticity modulus, toughness, and strain rate sensitivity index. A common finding was that the increase in the strain rate increased the mechanical response of the polymeric parts. The increase in the compressive strength reached 25% between the lowest and the highest strain rates the parts were tested for most polymers. Remarkable variations of deformation and fracture modes were also observed and documented. The current research yielded results with valuable predictive capacity for modeling and engineering modeling, which hold engineering and industrial merit.

Optimized titanium dioxide loading for properties of natural rubber latex and acrylic emulsion blends

Blends of prevulcanized natural rubber (PVNR) and acrylic emulsion (AC) were prepared at the fixed PVNR/AC ratio of 30/70. Effects of titanium dioxide (TiO2) addition were optimized across the contents 0, 10, 20 and 30 parts per hundred parts of polymer (php) with respect to various properties. Morphological analysis revealed a two-phase system in which the PVNR particles were dispersed in the AC matrix. Incorporation of TiO2 induced a finer blend morphology in which a part of the TiO2 was located at the interfaces of blend components. The tensile strength increased with initial TiO2 loading and reached its maximum at 10 php loading, with an improvement by about 127% over the blend without filler. However, further increase in filler loading reduced the tensile strength, and the filler tended to agglomerate at those higher loadings. Thermal stability and storage modulus in rubbery region of the blends containing TiO2 were also improved over the unfilled blend, due to the improved morphology and the hydrogen bonds between TiO2 filler and polymer matrix. TiO2 improved water wettability and adhesion of the blend. The maximum peel strengths on wood and metal substrates were about 120% and 26% larger than for the reference unfilled blend. Such drastic improvements suggest that the filled blends may find applications as coating materials.

Self-catalysed frontal polymerisation enables fast and low-energy processing of fibre reinforced polymer composites

Frontal polymerisation has the potential to bring unprecedented reductions in energy demand and process time to produce fibre reinforced polymer composites. Production of epoxy-based fibre reinforced polymer parts with high fibre volume content, commonly encountered in industry, is however hindered by the heat sink created by the fibres and the mould, overcoming the heat output of the chemical reaction, thus preventing front propagation. We propose a novel self-catalysed frontal polymerisation manufacturing method based on the integration of thin resin channels in thermal contact with the composite stack as a strategy for low-energy production of high fibre volume fraction polymer composites without the need for a continuous energy input. Frontal polymerisation inside the resin channel proceeds faster and preheats the fabric stack, thus catalysing the process. Parts with up to 60% fibre content are successfully produced independently of the sample thickness. Fillers added within the resin channels provide means to tailor the frontal polymerisation process kinetics. The parts have a significantly higher glass transition temperature than those produced in a conventional oven, and comparable mechanical properties while energy consumption is reduced by over 99.5%.

Mechanical investigation of compositing by resin filling in lattice structures manufactured with fused deposition modelling

Fused Deposition Modeling (FDM) is a widely used polymer additive manufacturing technique for polymer part manufacturing and prototyping. However, manufacturing speed, mechanical properties, and high costs, limit its suitability for industrial applications. In this study, researchers blended polyester and polyurethane resins with lattice structures to achieve a remarkable 70% reduction in production time and a 75% decrease in manufacturing costs. They explored five lattice structure geometries relevant to common literature applications. Lattice structures were manufactured using PA, PLA, PA-CF, and TPU filaments. The composite samples underwent comprehensive analysis, including SEM microscopic inspections, density measurements, and compression tests. Parameters such as density, yield strength, compressive strength, specific stress, modulus of elasticity, and toughness were evaluated. The findings revealed that polyester-based composites exhibited a remarkable 131% enhancement in mechanical properties, with toughness values increasing up to 12-fold. The results revealed significant mechanical advantages that the developed composites can offer in applications.