Thermoplastic Materials Research Articles

ANALYSIS OF THE POSSIBILITIES OF MANUFACTURING FUNCTIONAL ELEMENTS USING THE FFF METHOD

The article presents the course and results of research aimed at assessing the strength and practical usability of a furniture hinge additively manufactured from thermoplastic material. The research activities included: development of design assumptions, adoption of target geometry, creation of a 3D-CAD model, preliminary strength analysis in the FEM environment, prototype manufacturing using FFF method with thermoplastic material (pet-g), and conducting tests under conditions similar to real ones. The hinge geometry was based on typical market-available design solutions, while considering the specifics of the adopted manufacturing method. Strength analysis via FEM was conducted on the 3D-CAD model, allowing estimation of stress values and determination of the suitability of the developed geometry for testing on a real model. Subsequently, research models were produced using FFF technology with various infill patterns: linear 30%, hexagonal 30%, linear 60%, hexagonal 60%, and solid 100%. Bench tests were conducted to determine the maximum load-bearing capacity of the hinge under perpendicular loading to the axis and to assess hinge wear under conditions simulating real-life door usage. The results revealed that the hinge with solid infill safely carried a load of 160 kg without damage, while the hinge with hexagonal 30% infill exhibited the lowest load-bearing capacity, failing at 85 kg. To determine the hinge's durability, the clearance at two reference points on the doors was measured.

Comparison of low-velocity impact damage in laminated composites for two thermoplastic material systems

Aircraft manufacturers are investigating thermoplastic material systems to produce parts more quickly and efficiently. Detailed damage data is needed to evaluate existing damage analysis methods, developed for thermoset materials, to predict damage in thermoplastic materials. Damage maps were created for two thermoplastic material systems subjected to low-velocity impact over a range of impact energies. In this paper, the damage maps were used to investigate and compare the damage response of the different material systems. Impact specimens were manufactured from TC1225 LMPAEK T700G from Toray Industries and APC AS4D/PEKK-FC from Solvay. The effect of the degree of crystallinity on the damage response was also investigated using a third set of specimens manufactured using the Toray material and a quenching process. Using a combination of data obtained from X-ray computed tomography and ultrasonic testing, damage maps were created for every interface and ply for selected specimens showing matrix cracks, delamination outlines, and fractured fibers. The LMPAEK specimens were found to have fewer and smaller delaminations than the PEKK specimens for impacts at the same energy. However, the LMPAEK specimens contained a larger number of fiber breaks. A similar trend was observed when comparing low-crystallinity LMPAEK specimens with the baseline LMPAEK specimens. The LMPAEK specimens often contained lines of fiber fractures in near-surface plies emanating from the contact region that were not present in the PEKK specimens. The different damage responses may indicate that the material selection will be a function of the application and loading.

An evaluation of progressive damage analysis methods for modeling low velocity impact of thermoplastic composites

State-of-the-art progressive damage and failure analysis (PDFA) tools for composites were developed for thermoset materials because of the prevalence of the material system within the aerospace industry and the need to address damage growth behavior of composites analytically. As the presence of thermoplastic materials has started to grow in the industry, it is necessary to be able to predict their behavior as well. However, it is unclear whether existing tools based on linear elastic fracture mechanics (LEFM) can be used to represent thermoplastics. One application area for PDFA tools is low velocity impact (LVI). This work presents two PDFA modeling methods originally validated for predicting damage of thermoset composites in low-velocity impact and evaluates their ability to model a thermoplastic material system in the same scenario. Both methods use MAT299, a continuum damage mechanics material model, to represent interlaminar damage and a cohesive tiebreak definition within LS-DYNA to represent delamination within a laminate. The results reveal that the cohesive tiebreak modeling method, while successful in modeling thermoset materials, is not currently capable of predicting the delamination response of thermoplastics. The larger strain energy release rates for the thermoplastic material in combination with a deficiency in the modeling method are believed to be the cause of the reduced delamination in the simulations. Potential routes for improving the delamination prediction in the simulations include adjusting the mode-mixity behavior, using a different cohesive approach for delamination, developing new best practices for cohesive behavior, and incorporating further non-linearity into the material model.

Building Ultrastrong, Tough and Biodegradable Thermoplastic Elastomers from Multiblock Copolyesters Via a “Reserve‐Release” Crystallization Strategy

AbstractSimultaneously attaining high strength and toughness has been a significant challenge in designing thermoplastic elastomers, especially biodegradable ones. In this context, we present a class of biodegradable elastomers based on multiblock copolyesters that afford extraordinary strength, toughness, and low‐strain resilience despite expedient chemical synthesis and sample processing. With the incorporation of the semi‐crystalline soft block and the judicious selection of block periodicity, the thermoplastic materials feature low quiescent crystallinity (“reserve”) albeit with vast potential for strain‐induced crystallization (“release”), resulting in their significantly enhanced ultimate strength and energy‐dissipating capabilities. Moreover, a breadth of mechanical responses of the materials – from reinforced elastomers to shape‐memory materials to toughened thermoplastics – can be achieved by orthogonal variation of segment lengths and ratios. This work and the “reserve‐release” crystallization strategy herein highlight the double crystalline multiblock chain architecture as a potential avenue towards reconciling the strength‐toughness trade‐off in thermoplastic elastomers and can possibly be extended to other biodegradable building blocks to deliver functional materials with diverse mechanical performances.

Building Ultrastrong, Tough and Biodegradable Thermoplastic Elastomers from Multiblock Copolyesters Via a "Reserve-Release" Crystallization Strategy.

Simultaneously attaining high strength and toughness has been a significant challenge in designing thermoplastic elastomers, especially biodegradable ones. In this context, we present a class of biodegradable elastomers based on multiblock copolyesters that afford extraordinary strength, toughness, and low-strain resilience despite expedient chemical synthesis and sample processing. With the incorporation of the semi-crystalline soft block and the judicious selection of block periodicity, the thermoplastic materials feature low quiescent crystallinity ("reserve") albeit with vast potential for strain-induced crystallization ("release"), resulting in their significantly enhanced ultimate strength and energy-dissipating capabilities. Moreover, a breadth of mechanical responses of the materials - from reinforced elastomers to shape-memory materials to toughened thermoplastics - can be achieved by orthogonal variation of segment lengths and ratios. This work and the "reserve-release" crystallization strategy herein highlight the double crystalline multiblock chain architecture as a potential avenue towards reconciling the strength-toughness trade-off in thermoplastic elastomers and can possibly be extended to other biodegradable building blocks to deliver functional materials with diverse mechanical performances.

A novel thermoplastic material: Pre‐polymerized PMMA liquid resin and continuous glass fiber‐reinforced composite initiated by benzoyl peroxide/N,N‐dimethylaniline

AbstractThermoplastic PMMA was rarely exploited in continuous fiber‐reinforced composites due to its viscous high‐temperature molten fluid as well as pessimistic wettability into fiber fabric. Redox‐active polymerization is a green route to develop a new liquid PMMA resin at room temperature to provide an in situ curing with the advantages of energy saving and consumption reduction. In this paper, BPO/DMA was adopted as a redox initiator pair, and the effect of MMA:BPO:DMA ratio on curing time, Mn, Tg, and mechanical properties of PMMA were systematically studied. When the ratio of MMA:BPO:DMA is 200:1.2:1, PMMA‐200 achieved optimistic mechanical properties at 20°C (tensile strength, 64.7 MPa; tensile modulus, 3352 MPa; bending strength, 125.3 MPa; bending modulus, 3023 MPa). Moreover, the mechanical properties were further improved at low temperatures. The maximum tensile strength and tensile modulus were up to 97.43 and 4297 MPa (−40°C) respectively. The tensile strength (0°, 1103 MPa; 90°, 52.3 MPa) and tensile modulus (0°, 47.5 GPa; 90°, 14.2 GPa) of glass‐fiber‐reinforced PMMA composite at 20°C were found to be comparable with epoxy resin‐based composites and even higher at lower temperature. In summary, redox‐initiated PMMA and its fiber‐reinforced composites are promising thermoplastic materials as new lightweight alternatives.Highlights Preparation method of PMMA resin and glass fiber composite. Research on the mechanical properties, molecular weight, glass transition temperature, curing time, etc. of PMMA resin. Testing of mechanical properties of PMMA glass fiber composites at room temperature and low temperature. Current applications and prospects of PMMA glass fiber composites.

Masticatory function between chewing with and without wearing clear thermoplastic appliances

BackgroundClear thermoplastic materials are used in a variety of oral appliances. In some situations, patients may wear clear thermoplastic appliances while eating. However, the effect of wearing clear thermoplastic appliances on chewing efficiency is unknown. This study aimed to evaluate the differences in masticatory function between chewing with and without wearing clear thermoplastic retainers over a 6-month period, and its associated factors.MethodsThirty patients who received upper and lower clear retainers after debonding fixed appliances were examined for objective and subjective masticatory function at retainer delivery (T0), 3-month (T1), and 6-month follow-ups (T2) in two conditions: with and without wearing their retainers while chewing. The objective method used multiple sieves reported as the median particle size (MPS). The food intake ability (FIA) test served as the subjective method. Paired t-test was used to compare the outcomes between chewing with and without retainers at each evaluation time point. Repeated measures ANOVA followed by the Bonferroni post-hoc test was used to compare the outcomes between the three evaluating time points. Multivariable linear regression analysis was performed to assess whether age, sex, and extraction/non-extraction was associated with these effects.ResultsThe MPS was significantly greater when chewing with retainers compared with chewing without them at T0 (P < 0.05), however, it was not significantly greater at T1 and T2 (P > 0.05). The MPS with and without the retainers tend to decrease between T0, T1 and T2. In particular, the MPS while chewing with retainers significantly decreased between T0 and T1. The total FIA score and FIA subscores for hard and soft food were significantly lower when eating with retainers at T0 (P < 0.05), however, all FIA scores when eating without retainers did not significantly change between T0, T1, and T2. No significantly associated factors were identified.ConclusionsWearing clear retainers while chewing decreases objective and subjective masticatory function immediately after completing orthodontic treatment. However, this significantly improved to levels comparable to chewing without retainers after a 3-month follow-up. Age, sex, and extraction/non-extraction treatment were not associated with the difference in masticatory function while chewing with and without wearing the retainers.

Poly(arylene ether)s via Cu(II)-Catalysis.

Poly(arylene ether)s (PAEs) are a versatile class of thermoplastic materials with commercial importance. Currently their synthesis relies predominantly on either nucleophilic or electrophilic aromatic substitution reactions, severely limiting the scope of available PAEs. Herein, we report the copper(II)-catalyzed polycondensation of electronically unactivated aryl bromides with bisphenols to afford a wide range of new PAEs. These PAEs are characterized by their thermal and mechanical properties. Functional PAEs were produced that have reversible acid- and redox-triggered chromophores incorporated into the backbone, which illustrates the utility of these methods.

Investigation of Dynamic-Cyclic, Dynamic-Impact, and Timber-Construction-Relevant Characteristics of Wood–Textile Composites

Wood–Textile Composites (WTCs) are a new type of composite material based on willow wood strips and polypropylene that combines the properties of classic natural-fiber-reinforced polymers with an innovative textile wood design. While the basic quasi-static properties have already been investigated and described, there is a lack of knowledge about the behavior of the material under dynamic-cyclic and dynamic-impact loading as well as in relation to basic wood construction parameters. The present study is intended to contribute to the later use of the developed material, e.g., in architecture. For this purpose, fatigue tests, dart drop tests (impact and penetration), impact bending tests, and embedment tests were carried out. It was shown that embedding wood fabrics in a thermoplastic matrix leads to a significant increase in resistance to impact loads compared to the neat basic materials. It was also shown that the ratio of the failure stress in the fatigue test to the tensile strength of the WTC corresponds to that of other fiber-reinforced thermoplastics at around 70%. The embedment tests showed that WTC has good values compared to neat wood.

Rheology and Processing of High-Strength Liquid Crystal Polymer Reinforced Thermoplastic Composite Materials

Liquid crystal polymer (LCP) composites are presented as lightweight, high-strength, thermoplastic composites. Fumed silica (FS), carbon black (CB), carbon nanostructures (CNS), and boron nitride (BN) added to the polyphenylene sulfide (PPS) increased the viscosity ratio of the PPS to the LCP. PPS filled with 5 wt.% FS was used to optimize injection molding conditions and had a viscosity ratio ranging from 2 to 13. Increasing fill time to 5 s brought about the highest tensile strength of 99 MPa and modulus of 12.5 GPa, while the tool and melt temperatures imparted no significant effect. Mechanical and thermal properties of select LCP materials processed using molding conditions optimized for the experimental materials are presented. Mechanical properties in the crossflow direction were lower than in the flow direction, which could be overcome with tool design and placement of valve gates to tailor the flow patterns. BN filled composites increased the thermal conductivity to a value of 0.26 W/mK at 16 wt.% loading.

Ultra-high-rate Manufacturing of Thermoplastic Window Plug using Hybrid Overmolding

Highly loaded complex parts are machined from a solid block of metal by removing material through cutting, boring, drilling, and grinding to obtain the three-dimensional shape. Most cases, this involves removing as much as 80 percent of the material from a billet, which is time-consuming and inefficient considering the cost of the materials. Alternatively, these complex parts can be manufactured using hybrid overmolding process which involves injecting plastics over a reinforced substrate with continuous fiber-reinforcement eliminating subtractive machining or joining of multiple parts. The substrate is typically heated using an infrared (IR) oven and preformed over a solid mold to a three-dimensional shape using thermoforming. Injection overmolding material can also be reinforced with discontinuous fibers based on the design requirements. Both thermoforming and injection molding are matured automotive ultra-high-rate manufacturing processes. Adopting these technologies to aerospace requires advanced aerospace-grade thermoplastic material systems and developing the hybrid overmolding process that combines both thermoforming and injection molding processes. Material compatibility is one of the key enablers for the fusion across the overmolded interfaces. To demonstrate the overmolding technology for an aerospace application, Victrex AE250 low-melt polyaryletherketone (LM-PAEK) system reinforced with AS4 fibers and a 30% carbon fiber-reinforced polyetheretherketone (PEEK) were used to overmold aircraft window plugs to be used for cargo conversion of passenger aircraft. The fully automated overmolding process was demonstrated using KraussMaffei multi-robotic thermoforming and injection molding system. Thermal and mechanical test evaluations were employed to assess the material compatibility and overall part quality. Photomicrographs and flexure tests conducted on test samples extracted from the window plugs indicated satisfactory fusion across the overmolded interface and optimized holding of PEEK materials.

Advancements in Biofiller-Reinforced PLA Composites for 3D Printing: A Review

Additive manufacturing is key in realizing highly complex and high-performance composite materials. Among all the various kinds of functionality that could be added to a composite component, continuous fiber-reinforced composites have been drawing much attention because of their attractive combination of properties. The comprehensive spectrum of knowledge that ranges from the basics concerned with structure, morphology, synthesis, physical, and chemical properties finally reaches to this analytical study of advanced composites. Most generally, such a composite is structured on a thermoplastic or thermoset polymer matrix that embeds the load-carrying reinforcing fibers; probably best known are carbon, glass, and aramid fibers. These composites, which involve fibers continuously reinforcing, have high strength relative to their weight. They are also anisotropic, meaning they have qualities that vary from one direction to another – something which might be customisable for specific load cases. They warp and shrink less during their life in an outside environment than conventionally made bioplastics due to a fact that short fibers can provide reinforcement to them. This 3-D printing object is manufactured by special additive manufacture technology during the manufacturing process after compounding and extruding the fiber-reinforced composite filament. The final properties of 3D printed parts could be tailorable through changing variables such a fiber type, fiber length, volume fraction, polymer matrix material, orientation of fibers, and printing process parameters. These continuous fiber-reinforced 3D printed composites could achieve tensile strengths up to one GPa, have stiffness values reaching even a rating of countless Gpa, and have ad thicknesses in the range from about 1.4–1.8 g/cm³. This finding could be applied in basically all major industries, from aerospace and the automotive industry to sports gear. Such conclusions from the analysis may be useful in the selection of appropriate materials and techniques while even guiding the development of new applications with respect to such advanced composite materials.

Studying and analysis of deformation and stresses in horizontal-axis wind turbine using fluid-structure interaction method

Fluid-structure interaction (FSI) studies have become an important tool in the development of wind turbine blades as well as for analyzing and optimizing Horizontal Axis Wind Turbine (HAWT). The most essential elements for estimating the turbine blade strength to withstand extreme wind loads and aerodynamic performance are the blade deformation and the associated stresses. This study aims to compare the strength and analyze the deformation behavior of two models of HAWT blades. A three-dimensional model was created and loaded into a Finite Element (FE) model for analysis. The Computational Fluid Dynamics (CFD) investigation was coupled with the structural model using one-way FSI. In this article, the effect of the aerodynamics on the blade surface of a small HAWT has been studied numerically and experimentally. The airfoil used for the blade profile is S826 airfoil. To provide an appropriate displacement for static measurements, the blade in the experimental investigation is made of thermoplastic polyurethane material (TPU). It is noted that the current experimental findings verify the simulation results, and a comparison between the simulations and the experimental findings reveals a reasonable agreement. The numerical simulations are also implemented on a HAWT epoxy E-glass unidirectional (EEGUD) material. It can be concluded from this study that the blade deformation and stress on the blades are related to the wind speed. The deformation along the span length exhibits nonlinear variation that gradually increases from the blade root and reaches its maximum at the blade tip position. The tip deflection and equivalent stress were found to increase with an increase in wind speed. The dynamic analysis at different tip speed ratios shows the highest deformation at λ = 4, for wind speed of 20 m/s.

Evaluation of the use and performance of natural filler based polypropylene/leonardite composites

The use of polypropylene (PP), which has reached a considerably high level in the last century and is one of the polymers whose properties have been investigated and studied in much more detail with the use of various additives, can be obtained as composite structures with the use of both inorganic and organic additives, and the desired properties can be modified according to the desired purpose. In this study, it was aimed to evaluate the behavior of leonardite, a rich source of humic acid, with PP composite structures, whose performance with thermoplastic materials has never been investigated before, although there are studies on its use in different sectors. To evaluate the effects of different ratios of leonardite additives on PP polymer, the composites were prepared with a twin screw extruder, and the test specimens were produced using an injection molding device. Spectroscopic, density, microscopic, mechanical (tensile, impact, flexural), thermal and color analyses of composites containing leonardite at 0, 0.5, 1, 3, 5, and 10 wt% were carried out. As the amount of leonardite in the composite increased, a slight increase was observed in the density values of the composites, with a maximum of 4.7%. In microstructure analysis, a homogeneous distribution of the filler was observed in composites reinforced up to 1 wt%, while agglomeration occurred at higher rates. While the highest tensile strength and flexural strength values were found for the 5 wt% leonardite filled composite, it was observed that these values increased from 31.8 MPa to 32.7 MPa and from 32.84 MPa to 37.84 MPa compared to the pure PP, respectively. The highest Izod impact strength value was determined for the 10 wt% leonardite filled composite and an increase in this value was obtained from 2.47 kJ/m2 to 2.85 kJ/m2. The nucleation effect explains the decrease in supercooling temperature observed in the thermal analysis results. Furthermore, an increase of the thermal stability of PP/leonardite composite structures was demonstrated. When the color analysis results were examined, it was seen that the leonardite additive caused the color of the composite to darken, as expected.

A Sustainability Study upon Manufacturing Thermoplastic Building Materials by Integrating Chicken Feather Fibers with Plastic Waste

The article explains how to make thermoplastic construction materials by combining waste from chicken feathers with plastic waste. The initial phase focused on a new and environmentally friendly method of sterilizing raw feathers using microwave radiation inside sealed ovens with circulating air. Additionally, composites containing varying feather amounts using two different polymer matrices were fabricated through an injection process, followed by mechanical and physical tests on the samples. Because of their excellent characteristics, products made from a combination of chicken feather waste and plastic waste could effectively replace traditional wood–plastic composites that are polyvinyl chloride-based. The recycling technology was assessed for its environmental impact, and sustainability was proven economically and environmentally.

Comparison of mechanical and flammability properties of thermoplastic and thermoset matrix glass fibre woven fabric composites

This study aims to examine the mechanical and burning properties of composites made from twill (0°/0° and 0°/90° orientations) and plain fabrics using hybrid yarns produced by combining glass and polypropylene yarns with interwoven and intermingled methods. The properties of interwoven and intermingled hybrid fabric composites were compared with thermoset composites. Each composite (56% glass fibre content) plate is produced by combining eight fabrics with the same parameters using the press moulding technique. The effects of yarn and fabric weaving types on the results were examined in detail. When the results are examined, the breakage of glass fibres in intermingled hybrid yarns negatively affects the strength results. Therefore, composites made with intermingled hybrid yarn types and plain weave types of fabric had the lowest tensile strength value (132 MPa). The composite of twill woven fabrics produced with interwoven yarns arranged in 0°/0° orientation had the highest tensile strength of 315 MPa, and these results were very close to those of thermoset composites. Although the 0°/90° oriented twill composite showed a 2.3 times lower tensile strength value than the 0°/0° oriented twill composite, it had a 7.7 times higher value when bending strength values were taken into account. The main reason for this is that glass fibres contribute to the warp and weft directions. It has been observed that the composite consisting of plain fabrics woven with commingled hybrid yarns had the highest impact resistance. Additionally, when the combustion results were examined, it was concluded that the type of yarn and fabric weaving affected the burning rate. The slower combustion of hybrid commingled yarn composites resulted from fibreglass breakage during yarn production. These findings provide valuable insights into optimizing composite materials for specific applications, considering factors such as weaving pattern, fibre orientation, and mechanical performance.

Performance of photovoltaic panels with different inclinations under uniform thermal loading

Integrating photovoltaic (PV) panels with different tilt angles in building envelopes or roofs is widely employed for environmental sustainability. However, little is known about the influence of different tilt angles on the thermal failure of the photovoltaic façades or roofs in fire conditions. A total of 15 four-edge shielded PV panels (300 × 300 × 4.7 mm3), with five different inclinations of 0°, 15°, 30°, 45° and 60°, were heated to fail using a uniform radiant panel. Measurements were taken to track glass thermal breakage, surface temperatures, incident heat flux and failure characteristics. The glass fracture and pyrolysis of the internal thermoplastic materials were observed under thermal radiation. The average breakage time of glass in PV panels showed an increasing trend with increasing inclination of the PV panels. Moreover, when the PV panels were tilted beyond 30°, the time to failure increased more significantly. The maximum temperature difference and heat flux that the PV panels can withstand were primarily measured within the range of 61–84 °C and 8–15 kW/m2, respectively. Finally, the test results were simulated by a finite element method (FEM) model, calculating the heat transfer and thermal stress of PV panels: the average errors concerning temperature distributions and failure times were smaller than 15 % compared with the experimental results.

Effect of carbon nanotube on the mechanical properties of short carbon fiber reinforced polyether-ether-ketone

Additive manufacturing provides a quick and cost-effective way for the fabrication of complex composite structures. Additively manufactured short carbon fiber reinforced polyether-ether-ketone (SCF/PEEK) is a promising thermoplastic composite material due to its excellent designability, ease of manufacture, and good recyclability. However, the mechanical properties of 3D printed SCF/PEEK are unsatisfactory due to the layer-by-layer forming process. In this study, CNTs were introduced to 3D printed SCF/PEEK, and the influence mechanism of CNTs on the mechanical properties was analyzed and discussed in depth. The results showed that the introduction of CNTs could effectively enhance the tensile modulus of 3D printed SCF/PEEK, whilst it led to a decrease in the tensile strength and interlaminar shear strength of the composites. This was mainly related to the poor dispersion and agglomeration of CNTs. The modulus of 3D printed SCF/PEEK reached about 5.17 GPa, representing a 95.1% increase.

Investigation of Effect of Part-Build Directions and Build Orientations on Tension-Tension Mode Fatigue Behavior of Acrylonitrile Butadiene Styrene Material Printed Using Fused Filament Fabrication Technology.

This article explores the fatigue characteristics of acrylonitrile butadiene styrene (ABS) components fabricated using fused filament fabrication (FFF) additive manufacturing technology. ABS is frequently used as a polymeric thermoplastic material in open-source FFF machines for a variety of engineering applications. However, a comprehensive understanding of the mechanical properties and execution of FFF-processed ABS components is necessary. Currently, there is limited knowledge regarding the fatigue behavior of ABS components manufactured using FFF AM technology. The primary target of this study is to evaluate the results of part-build directions and build orientation angles on the tensile fatigue behavior exhibited by ABS material. To obtain this target, an empirical investigation was carried out to assess the influence of building angles and orientation on the fatigue characteristics of ABS components produced using FFF. The test samples were printed in three distinct directions, including Upright, On Edge, and Flat, and with varying orientation angles ([0°, 90°], [15°, 75°], [30°, 60°], [45°]), using a 50% filling density. The empirical data suggest that, at each printing angle, the On-Edge building orientation sample exhibited the most prolonged vibrational duration before fracturing. In this investigation, we found that the On-Edge printing direction significantly outperformed the other orientations in fatigue life under cyclic loading with 1592 loading cycles when printed with an orientation angle of 15°-75°. The number of loading cycles was 290 and 39 when printed with the same orientation angle for the Flat and Upright printing directions, respectively. This result underscores the importance of orientation in the mechanical performance of FFF-manufactured ABS materials. These findings enhance our comprehension of the influence exerted by building orientation and building angles on the fatigue properties of FFF-produced test samples. Moreover, the research outcomes supply informative perspectives on the selection of building direction and building orientation angles for the design of 3D-printed thermoplastic components intended for fatigue cyclic-loading applications.

Semi-Alicyclic Thermoplastic Polyimide Matrixes Based on Hydrogenated Pyromellitic Dianhydride and Asymmetrical 3,4′-Oxydianiline with Good Thermal Stability and Improved Optical Transparency

Thermoplastic polyimide (PI) matrixes, including PI-a (cc-34ODA) and PI-b (ct-34ODA) were prepared via the hot-pressing procedures of the resins derived from the 3,4′-oxydianiline (34ODA) and two alicyclic dianhydrides of 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride (ccHPMDA) and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride (ctHPMDA), respectively. The resins exhibited thermoplastic features with good formability at higher temperatures. The afforded semi-alicyclic PI sheets exhibited enhanced properties in comparison to commercially available, wholly aromatic thermoplastic PIs, such as PI-ref1, which are derived from 3,3′,4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-oxydianiline (44ODA), as well as PI-ref2, which is based on pyromellitic dianhydride (PMDA) and 4,4′-bis(3-aminophenoxy)biphenyl (mBAPB). In addition, the developed PI sheets exhibited high heat deflection temperatures (HDT) of 267.4 °C for PI-a and 268.6 °C for PI-b. There values were significantly higher when compared with those of PI-ref1 (Ratem® YS20, HDT: 239.0 °C), PI-ref2 (Aurum® PL450C, HDT: 238.0 °C), PI-ref3 (Ultem® 1000, HDT: 206.0 °C), PI-ref4 (Therplim® TO65, HDT: 180.0 °C), and PI-ref5 based on phthalic anhydride-terminated fluorinated PIs (HDT: 215.0 °C). In terms of mechanical properties, the current PI sheets showed superior flexural properties among the polymers with the flexural strength of 189.0 ± 11.7 MPa (PI-a) and 200.5 ± 4.2 MPa (PI-b), respectively. In addition, the PI sheets exhibited comparable compression properties, inferior impact strength, and tensile properties compared with the referenced PI counterparts. Basically, the PI-b sheet showed better comprehensive properties than those of the stereoisomeric PI-a analog.