Increase In Tensile Strength Research Articles

Development and Characterization of Milled Carbon Fiber-Reinforced Polypropylene Filaments for Fused Deposition Modeling: Mechanical Performance, Moisture Absorption, and Morphological Insights.

Abstract This study explores the production, characterization, and performance evaluation of carbon fiber-reinforced
polymer (CFRP) composite filaments designed for fused deposition modeling (FDM) applications. The primary
objective was to investigate the influence of milled carbon fiber (MCF) content on the mechanical, moisture
absorption, and morphological properties of polypropylene (PP)-based composites. Composite filaments were
produced by blending micro-sized MCFs with PP granules, followed by a two-step extrusion process to create
filaments with varying MCF contents (1–24 wt.%). Test specimens were fabricated using 3D printing to evaluate
the performance of the composite materials.
The results demonstrated a significant enhancement in mechanical properties compared to neat PP. The composite with 9.09 wt.% MCF achieved optimal performance, exhibiting increases in tensile and flexural strengths
by 74% and 99%, respectively, relative to neat PP. However, higher MCF contents (16 and 24 wt.%) led to
reduced mechanical properties due to insufficient fiber-matrix adhesion, resulting in fiber pull-out. Moisture absorption studies revealed that the inclusion of MCFs increased the water uptake of the composites, with higher
fiber concentrations correlating to greater moisture absorption.
These findings underline the potential of MCF-reinforced PP composites for applications requiring improved
mechanical performance, such as lightweight structural components. The study identifies an optimal fiber content
of 9.09 wt.% for maximizing strength while minimizing moisture-related trade-offs. Future efforts could focus
on enhancing fiber-matrix bonding to improve performance at higher fiber concentrations.

Mechanical Strength Optimization of HDPE Biocomposite with Water Hyacinth Fiber Reinforcement using a Dispersing Agent

This study investigates the impact of a polyamine amides dispersing agent (BYK W-980) on the mechanical performance of the High-Density Polyethylene/Water Hyacinth Fiber (HDPE)/(WHF) composites. The dispersing agent was employed to improve the fiber distribution, enhance the fiber-matrix interaction, and reduce the fiber agglomeration, which negatively affects the mechanical properties of the composite. The Scanning Electron Microscopy (SEM) analysis revealed that the dispersing agent, particularly DA2, effectively minimized fiber agglomeration and promoted a more uniform fiber distribution within the HDPE matrix. The density testing indicated a reduction in porosity and an increase in composite density following the dispersing agent treatment. The mechanical testing demonstrated significant improvements with DA2 yielding the optimal results: a 19.54% increase in tensile strength, a 24.33% increase in flexural modulus, and an 18.53% increase in impact strength. The X-ray Diffraction (XRD) analysis showed an increase in the crystallinity index of the WHF, suggesting enhanced structural regularity, which supported the observed improvements in mechanical performance. Overall, the utilization of the polyamine amides dispersing agent, particularly DA2, significantly enhanced the mechanical properties and fiber-matrix interaction of the HDPE/WHF composites.

Enhancing fruit preservation with sodium alginate films incorporating propolis extract and graphene oxide.

In this work, sodium alginate (SA) composite films containing propolis extract (PRO) and graphene oxide (GO) were developed. Subsequently, the effects of PRO and GO on different properties of SA composite films were studied, and the films were characterized by scanning electron microscopy, fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. The PRO release properties and fruit preservation performance of the developed composite films were also investigated. The results showed that the incorporation of PRO resulted in a 51.16% increase in tensile strength. The simultaneous incorporation of PRO and GO reduced water vapor permeability (WVP) by 22.56% compared to the SA film. The temperatures at which the SA/GO/PRO film lost 5% of its weight were 8.0°C higher than those of the SA film. The incorporation of GO into the SA/PRO composite film also modulates the release of PRO. Furthermore, the incorporation of PRO and GO improved the tensile strength of the SA film, as reflected in the microstructure of the films. The reduced WVP of the SA composite film allowed the packaged blueberries to exhibit less weight loss and shrinkage, thereby prolonging their shelf life.

The Effect of Phosphoric Acid on the Flame Retardancy and Interfacial Adhesion of Carbon Fiber with Thermoplastic Resin PA6

This study investigated the effect of phosphoric acid treatment on carbon fibers to enhance their flame retardancy, the impact of carbon fiber surface treatment conditions on the interfacial adhesion between carbon fibers and PA6, and the chemical reaction mechanisms on the carbon fiber surface. Phosphoric acid treatment resulted in a flame-retardant effect, with a limited oxygen index of over 52.8%, and V0 level flame retardancy characteristics in the UL-94 test when the concentration exceeded 0.5 vol.%. When the treatment time was fixed at 30 min, the tensile strength increased by approximately 2%, and the interfacial shear strength (IFSS) increased by approximately 11% at 0.5 vol.% phosphoric acid, accompanied by an increase in hydroxyl (C–O), carbonyl (C=O), phosphate (P–O), and phosphoryl (P=O) groups. However, at concentrations higher than 0.5 vol.%, the tensile strength decreased by approximately 90%, and the IFSS decreased by approximately 12%, compared to the untreated nonwoven fabric. When the treatment time was varied at 0.5 vol.% phosphoric acid, both the tensile strength and IFSS increased continuously up to 10 min, with a 31% increase in tensile strength and a 17% increase in IFSS, along with an increase in O=C–O, P–O, and P=O groups, as well as surface energy. After 10 min, the tensile strength decreased by approximately 20%, while the IFSS and surface energy remained relatively unchanged.

Enhancement of Sansevieria Trifasciata Laurentii Fiber Properties with Liquid Smoke Treatment

ABSTRACT This study aimed to investigate the potential of liquid smoke-treated Sansevieria Trifasciata Laurentii fiber (STLF) as a reinforcement in polymer composites. The research method consisted of soaking STLF in grade 3 liquid smoke (LS) for 1, 2, and 3 hours, then drying the fibers in an oven at 40°C for 30 minutes. The treated fibers were characterized by single-fiber tensile strength, morphology, chemical composition, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show that treating STLF fibers with liquid Smoke (LS) for 2 hours results in a 2.60% increase in tensile strength and a 64.20% improvement in crystallinity compared to untreated fibers (TP). The LS treatment also modifies the fiber surface morphology, creating a pattern of longitudinal lines and resulting in a cleaner, rougher, and more porous fiber structure. In addition, LS treatment introduces C=C and C=O functional groups into the STLF molecular chain, potentially improving the interfacial bonding between the fiber and the polymer matrix.

Evaluation of mechanical and wear properties of LM24/fly ash/titanium diboride hybrid metal matrix composites using stir casting

This study focuses on the development of novel hybrid composites based on the LM24 alloy, utilizing liquid metallurgy stir casting to incorporate dual reinforcements (titanium diboride (TiB2) and fly ash (FA)). The weight percentage of TiB2 was maintained at levels of 2.5%, 5%, and 7.5%, keeping the FA at 2.5% during the course of fabrication. The introduction of 7.5 wt% TiB2 and 2.5 wt% FA displayed a very notable 43.18% increase in hardness and a 21.53% increase in tensile strength of the hybrid composite compared to the LM24 alloy. Furthermore, hybrid composites with a total reinforcement of 10 wt% exhibited superior wear resistance across the entire range of applied loads. Tensile fractography revealed ductile fracture mode for the LM24 alloy, while hybrid composites displayed a mixed-mode fracture. High-load-induced abrasive wear with little plastic deformation was seen on worn surfaces of hybrid composites, whereas adhesive wear was the dominant type of wear in the LM24 alloy. The results show that hybrid composites have better mechanical and tribological properties because the reinforcement particles are well distributed and the load is transmitted optimally. However, it is noted that increased reinforcement levels lead to a reduction in ductility, resulting in decreased impact resistance for the hybrid composites.

Heat-Responsive PLA/PU/MXene Shape Memory Polymer Blend Nanocomposite: Mechanical, Thermal, and Shape Memory Properties

This study investigates the fabrication and characterization of heat-responsive PLA/PU/MXene shape memory polymer blend nanocomposites with varying PLA content (10, 20, 30, and 50%) and a fixed MXene content of 0.5 wt.%. The results indicate significant improvements in mechanical properties, with the 50% PLA/PU/MXene blend showing a 300% increase in ultimate tensile strength and a 90% decrease in % elongation compared to pure PU. Additionally, the 50% blend exhibited a 400% increase in flexural strength. Microstructural analysis revealed dispersed pores and sea–island morphology in pure PU and the 50% PLA/PU/MXene blend. Thermal analysis using DSC showed an increase in crystallinity from 33% (pure PU) to 45% for the 50% PLA/PU/MXene blend, indicating enhanced crystalline domains due to the semi-crystalline nature of PLA and MXene’s influence on molecular ordering. TGA demonstrated a significant improvement in thermal stability, with the onset temperature rising from 185 °C (pure PU) to 212 °C and the degradation temperature increasing from 370 °C to 425 °C for the 50% blend, attributed to the rigid structure of PLA and MXene’s stabilizing effect. Shape memory testing revealed that the 30% PLA/PU/MXene blend achieved the best shape fixity and recovery with optimal performance, whereas higher PLA content diminished shape memory behavior.

Experimental Study on the Anti-Scouring Characteristics of Bedrock in Engineering Reservoir Areas That Are Conducive to Sustainable Development

High-speed water flow conditions can cause erosion of the bedrock in engineering areas. Due to the lack of accurate evaluation of bedrock scour and erosion rates, there has been a consumption of manpower and resources without achieving satisfactory engineering outcomes. Therefore, studying the scouring and erosion effects of water flow on bedrock is of significant importance for maintaining the sustainable development and safety of engineering projects. Using the bedrock prototype from the Xiaonanhai site in the upper reaches of the Yangtze River, a model test device was developed to conduct anti-scour tests on the bedrock. The study quantitatively examined the basic physical properties, incipient erosion velocity, and erosion rates of different types of bedrock. The study found that the prototype bedrock under natural exposure, submerged immersion, and alternating wet and dry conditions showed a trend of decreased tensile strength, with the alternating wet and dry conditions being the most detrimental to maintaining the physical properties of the rock mass. The anti-scour velocity of silty claystone and clayey siltstone samples increased with the increase in tensile strength, and the erosion rate increased with the increase in shear stress. If the shear stress is kept constant, the erosion rate decreases with the increase in tensile strength. The erosion rate is inversely proportional to the ratio of the bedrock’s tensile strength to the riverbed shear stress, with the fitting relationship showing a piecewise linear distribution. The research results can provide guidance for the safe production of engineering involving bedrock erosion in engineering reservoir areas that are conducive to sustainable development.

Two‐dimensional layered MoS2/lignin as additives for epoxy composites with improved mechanical and tribological properties

AbstractThe MoS2/lignin hybrid material was successfully synthesized and incorporated into an epoxy resin to fabricate composite coatings. The results demonstrate that MoS2 is uniformly attached to the surface of lignin sheets. Compared to adding lignin alone, the MoS2/lignin hybrid‐epoxy resin (EP) composite coatings exhibited enhanced friction‐reducing and wear‐resistant properties. Specifically, the 1 wt% MoS2/lignin hybrid displayed excellent dispersion and high interfacial compatibility within the resin matrix, leading to a 66.7% increase in Vickers hardness, a 27.5% increase in tensile strength, and a 73.9% improvement in char yield. Furthermore, the friction coefficient and wear rate were reduced by 63.2% and 75.8%, respectively. As a uniformly dispersed hybrid structure, the MoS2/lignin material can endure higher loads, autonomously repair defects, and form a stable and complete transfer film on the worn surface, demonstrating synergistic friction‐reducing and wear‐resistant effects within the epoxy resin matrix. Integrating MoS2 into a two‐dimensional material can provide a practical reference for designing polymer‐based hybrid materials with outstanding comprehensive properties.Highlights The MoS2/lignin hybrid material was successfully synthesized. MoS2 is uniformly attached to the surface of lignin sheets. The hybrid significantly enhances friction‐reducing and wear‐resistant properties. Vickers hardness increased by 66.7%, and tensile strength increased by 27.5%. The friction coefficient was reduced by 63.2%, and the wear rate was reduced by 75.8%.

Welding speed effects in underwater and conventional friction stir welding of dissimilar aluminum alloy 6061-T6 and 5083-H12 joints

This study investigates the influence of welding speed on the mechanical and microstructural properties of dissimilar aluminum alloy joints (AA6061-T6 and AA5083-H12) joined using Underwater Friction Stir Welding (UFSW) and Conventional Friction Stir Welding (CFSW). The experiments were conducted at a constant tool rotation speed of 1120 rpm and varying welding speeds (20 to 80 mm/min). Results showed that UFSW achieved peak temperatures 13% lower than CFSW. Moreover, the generated peak welding temperature was inversely proportional to welding speed in UFSW and CFSW. Optimal performance was observed at 63 mm/min, where UFSW produced an 89% reduction in intermetallic compound (IMC) thickness and a 21% finer grain size compared to CFSW. Additionally, UFSW joints exhibited a 10.20% increase in tensile strength and a 7% increase in hardness over CFSW. The enhanced cooling effect in UFSW contributed to these improvements, yielding more uniform material flow, refined microstructure, and reduced IMC formation. These findings suggest UFSW as a superior technique for achieving high-quality dissimilar aluminum alloy joints, with significant enhancements in mechanical properties and microstructural refinement.

Effect of friction stir processing on wire arc additively manufactured ER70S-6/SS308L bimetallic FGM

In this research, wire arc additive manufacturing (WAAM) is employed to fabricate a bimetallic steels component using ER70S-6 and SS308L. However, this process involves high power densities and significant heat inputs, which elevate the risk of unfavorable grain structures and defects. To mitigate this issue, friction stir processing (FSP) is applied, utilizing a unique tool featuring a flat shoulder without a pin. The resulting samples undergo testing for mechanical and metallurgical properties. The microstructure of ER70S-6 reveals ferrite with small amounts of pearlite at the grain boundaries. The upper portion of the deposited sample exhibits more pronounced grain refinement compared to the lower section, largely due to the rapid cooling rate and thermal cycling effects during layer deposition. This grain refinement is attributed to dynamic recrystallization, which enhances the hardness of the FSP-treated sample relative to its initial as-deposited state. Tensile tests indicate a significant increase in tensile strength, accompanied by a reduction in percentage elongation after FSP. The fatigue crack growth rate is higher along the longitudinal direction of bi-metallic joint as compare to transverse to the joint.

Extraction of lignin from Duabanga grandiflora and its valorization for nanocomposite development with enhanced mechanical and UV shielding properties

Abstract In this study, we report on extracting lignin from Duabanga grandiflora (Khukon), an untapped wood source, and its transformation into nano-lignin (NL) to create durable and thermally stable composites. Utilizing ultrasonication, we synthesized spherical lignin nanoparticles with an average size of 8 nm, as verified by high-resolution transmission electron microscopy. These nanoparticles were integrated into a polyvinyl alcohol (PVA) and guar gum (GG) matrix, resulting in PVA-GG-NL (PGNL) composites. PVA-GG nanocomposite films containing various contents of lignin nano-particles (1, 2 and 3 wt%) were formulated by a simple solvent cast method and cross-linked by adding borax. Addition of 1 wt% lignin nanoparticles brought in the composite films with 29.8 MPa tensile strength and 139.3% elongation at break. Compared to PVA-GG-lignin composites, the PGNL composites exhibited a 59.4% increase in tensile strength and enhanced elongation at break and good thermal degradation properties. Notably, the PGNL composite films were transparent but could shield 99.9% of the UV-A (320–400 nm) and UV-B (280–320 nm) radiations, marking a significant advancement in UV protective materials. Our innovative use of D. grandiflora-derived NL in a dual-polymer network not only underscores the potential of renewable resources in high-performance applications but also aligns with the principles of a circular bioeconomy by offering a sustainable solution for effective UV protection.

Mechanical Properties and Prediction Based on ANN Model of Basalt and Polypropylene Fiber Reinforced Concrete

Objectives: Utilization of steel fiber increases concrete strength and ductility however, the cost of steel fiber is high and ultimately leads to an increase in the cost of concrete. Basalt fiber is a new type of fiber with high strength and toughness and can effectively replace the place of steel fibers. In this paper, concrete reinforced with polypropylene fibers and basalt fibers was tested for its mechanical properties and compared with the same predicted through a simulated model created by the Artificial Neural Network. Methods: The percentage of polypropylene fiber was kept at 0.25%, and different amounts of basalt fiber were added as 0%, 0.25%, 0.5%, 0.75%, and 1%. Based on traditional testing methods compressive strength, tensile strength, and flexural strength of normal concrete, Fiber reinforced concrete and Hybrid fiber reinforced concrete have been found. To forecast the concrete qualities, the model was simulated after the datasets were trained using a neural network fitting tool. Findings: In comparison to concrete that had only 0.25% polypropylene fiber, a hybrid fiber-reinforced concrete mix including 0.5% basalt fiber and 0.25% polypropylene fiber demonstrated a 9.69% improvement in compressive strength. In comparison to the concrete made only of polypropylene, the mix containing 0.25% polypropylene fiber and 0.75% basalt fiber showed a 26.12% increase in flexural strength and a 39.25% increase in split tensile strength. The error percentage between predicted and experimental values is below 10%. Novelty: Utilization of basalt fiber in concrete is very rare and this proposed work focused on the hybridization of basalt fiber in the place of steel fibers, which is prone to corrosion and reduces the cost of material effectively. The concrete's flexural and tensile strengths were significantly increased by the addition of basalt fibers. The mechanical characteristics of hybrid fiber-reinforced concrete are well predicted by the simulated ANN model. Keywords: Basalt fiber, Polypropylene fiber, Artificial Neural network, Fiber reinforced concrete, Hybridization

Comparative Study of Agricultural Wastes Utilization in Cementitious Composites

ABSTRACT The exploration of alternative solutions for natural concrete aggregates is justified in the context of sustainable development and the circular economy. This research seeks to assess the effects on physical, mechanical, and thermal characteristics by incorporating walnut shells (WS), corncobs (CC) and cellulose fibers (CF) as substitutes for fine aggregates in concrete, as opposed to using regular concrete. Various proportions (5%, 10%, and 15% by weight) of each agricultural waste were introduced, resulting in a decrease in concrete density as their ratio increased. Also, the connection between mechanical and thermal properties and the type of agricultural waste used were established for all concrete mixes. In the case of walnut shell, there was an increase in compressive, flexural, and split tensile strength. Furthermore, corncobs showed an increase in most of mechanical properties but only up to 10 wt.% ratio and after that ratio a drop in value was noted. Similar trends to the ones presented in mechanical tests were noted during thermal properties tests. This study also identified correlations between density and compressive strength in concrete incorporating three types of agricultural waste.

Improvement adhesion durability of epoxy adhesive for steel/carbon fiber-reinforced polymer adhesive joint using imidazole-treated halloysite nanotube

Surface treatment is essential for enhancing adhesion durability and minimizing substrate damage in hybrid structural materials. This study focuses on developing a hybrid adhesive lap joint by incorporating halloysite nanotube (HNT) with imidazole-functionalized surfaces (IM-HNT) into epoxy adhesives to improve adhesion performance and thermal shock resistance. The surface treatment of HNT with imidazole (IM) introduced a curing catalyst effect, reducing activation energy by 50% and accelerating curing time by 90%, as confirmed by Kissinger’s plot and permittivity measurements. The optimized IM-HNT content improved thermal stability by controlling thermal expansion and enhanced mechanical properties, achieving a 15% increase in tensile strength and a 50% enhancement in fracture toughness. The adhesion performance of steel/carbon fiber-reinforced polymer (CFRP) hybrid joints was evaluated through single-lap shear tests, demonstrating a 25% improvement in shear strength. Adhesion durability was tested under cyclic thermal shock conditions, showing a 30% increase as IM-HNT content increased. Finite element analysis (FEA) revealed reduced residual stress at the adhesive interface, supporting the enhanced thermal and mechanical robustness. This study highlights the potential of surface-treated halloysite nanotubes in hybrid adhesive lap joints to significantly improve adhesion durability and thermal shock resistance, addressing critical requirements for hybrid structural materials.

Enhancing black mulberry storage with sodium caseinate and gum tragacanth edible films

A bright future lies ahead for the application of natural biocomposites in the food industry. In this research, edible biocomposite films were created using sodium caseinate (SC)-gum tragacanth (GT) and incorporating carum carvi seed essential oil (EO) as a nanoemulsion. Different ratios of oil were used as variables. The physical properties, structural morphology, mechanical characteristics, and thermal behavior of the films were evaluated. Furthermore, the preservative effects of these edible films were studied to prolong the shelf life of black mulberries over a period of 10 days at 4 °C. The findings indicated that the increase of EO content to the edible films resulted in a significant increase in thickness, tensile strength, opacity and water vapor permeability. Conversely, the elongation at break, water solubility and moisture content decreased with the rise in oil content up to 3.9%. Also the visual appearance and sensory evaluation of the fruits revealed that black mulberries covered with edible films containing 2.6 and 3.9% oil were more preferred compared to the other groups. The integration of caraway oil into the SC-GT biocomposite has been investigated for the first time, demonstrating that the resulting films are effective in prolonging the shelf life of black mulberries.

Synthesis of multi‐element flame retardant hydrazides and its modification to epoxy resin

AbstractWhen flame retardants are added to epoxy resins (EP) to enhance their flame retardancy, it often results in a negative impact on the mechanical properties of itself. In order to solve this problem, a new reactive flame retardant multi‐element hydrazides (BSD) is synthesized by using benzenesulfonohydrazide and diphenylphosphinic chloride as raw materials, it can play a flame retardant effect through the synergistic effect of P\N\S multi‐elements, and at the same time, a large number of secondary amine groups in the structure of BSD can produce strong hydrogen bonding interactions with the hydroxyl groups of the molecular chain of EP. The experimental results proved that the incorporation of only 3 wt% of BSD enabled EP to achieve a UL‐94 V‐0 rating. Furthermore, when the amount of BSD is increased to 5 wt%, the values for peak heat release rate (PHRR) and total heat release showed a reduction of 26% and 20.8%, ultimately maximizing the limiting oxygen index to 34.9%, showing exceptional efficiency. In the meantime, it showed a 37.3% increase in flexural strength and a 21.4% increase in tensile strength, and the transparency of the modified epoxy resin was still maintained at this time. In summary, introducing BSD into EP obtains a highly efficient reinforced flame retardant epoxy resin (FREP).Highlights A P/N/S‐containing hydrazide to improve the flame retardant of EP. When the P content is 0.25 wt%, the FREP reaches UL‐94 V‐0 grade. Tensile and flexural strength increased by up to 21.4% and 37.3%. With the addition of BSD, the FREP still show high transparency.

Zero Waste Concept in Production of PLA Biocomposites Reinforced with Fibers Derived from Wild Plant (Spartium junceum L.) and Energy Crop (Sida hermaphrodita (L.) Rusby).

This research follows the principles of circular economy through the zero waste concept and cascade approach performed in two steps. Our paper focuses on the first step and explores the characteristics of developed biocomposite materials made from a biodegradable poly(lactic acid) polymer (PLA) reinforced with natural fibers isolated from the second generation of biomass (agricultural biomass and weeds). Two plants, Spartium junceum L. (SJL) and Sida hermaphrodita (SH), were applied. To enhance their mechanical, thermal, and antimicrobial properties, their modification was performed with environmentally friendly additives-linseed oil (LO), organo-modified montmorillonite nanoclay (MMT), milled cork (MC), and zinc oxide (ZnO). The results revealed that SH fibers exhibited 38.92% higher tensile strength than SJL fibers. Composites reinforced with SH fibers modified only with LO displayed a 27.33% increase in tensile strength compared to neat PLA. The addition of LO improved the thermal stability of both biocomposites by approximately 5-7 °C. Furthermore, the inclusion of MMT filler significantly reduced the flammability, lowering the heat release rate to 30.25%, and enabling the categorization of developed biocomposite in a group of flame retardants. In the second step, all waste streams generated during the fibers extraction process are repurposed into the production of solid biofuels (pellets, briquettes) or biogas (bio)methane.

3D printable piezoelectric composites manufactured via scalable and sustainable solvent-free multi-extrusion process

Abstract The study presents the development of 3D printable lead-free particulate piezocomposites by implementing a solvent-free multi-extrusion process (MEP) to address the scalability limitations and safety concerns of solvent-based processing commonly used with highly resilient fluoropolymer polyvinylidene fluoride (PVDF) and its copolymers (e.g. with hexafluoropropylene (HFP)). Composite filaments of PVDF-HFP with ferroelectric barium titanate (BTO) particles at 20, 40 and 60 wt% were manufactured for fused filament fabrication (FFF) by applying the melt-based process consisting of effectively composed multiple extrusion and granulation cycles. The results from TGA, DSC, FTIR, XRD, EDS-SEM and tensile tests indicate that physical and mechanical properties of the re-extruded and printed PVDF-HFP are largely preserved. The process ensures homogeneous BTO dispersion within the consistently printable piezocomposites, which demonstrate satisfactory levels of piezoresponse and flexibility together with filler-reinforcing and high-field poling capabilities. The FFF-printed piezocomposites tested at higher strain rates (up to 0.17 s-1) exhibit 30–40% increase in tensile strength at the expense of reduced ductility. Brief thermal poling at 80 ○C and 20 kV/mm is observed to improve coefficient d33 through more effective BTO polarization compared to room-temperature poling (up to 7.3 pC/N is measured for the 40/60 wt% PVDF-HFP/BTO). Thermal poling also enhances piezoresponse stability by minimizing depolarization (d33 decay) regardless of poling duration. Increase in BTO content results in stronger dependence of piezoresponse on poling field, temperature and duration, as well as weaker dependence of ductility characteristics on the strain rate. The MEP approach is environmentally and economically sustainable manufacturing method that is accessible to a wide FFF user community. It is also scalable to high-throughput production of functional composites based on thermally resistant materials to enable 3D printing of customizable piezoelectric sensing devices.

Preparation of high-performance red fluorescent epoxy resin films guided by rare earth europium

Epoxy resins offer broad applications but are limited by their mechanical strength. This study enhances the properties of an indole-based epoxy resin (EPI) through the incorporation of europium ions (Eu3+), leveraging their cation-π interactions. A red fluorescent indole-based epoxy resin (Eu@HEr) was synthesized, emitting at 616 nm under Ultraviolet (UV) light. Eu@HEr exhibited a 42% increase in tensile strength (86 MPa) and a 114% improvement in elongation at break (10.9%) compared to EPI. The thermal decomposition temperature of Eu@HEr rose by 64 °C, indicating superior thermal stability. These findings highlight the potential for high-performance epoxy resins with dual mechanical and luminescent properties.