Search Results (864)

This narrative review examines contemporary applications of polymeric materials in dentistry from 2020 to 2025, spanning prosthodontics, restorative dentistry, orthodontics, endodontics, implantology, diagnostics, and emerging technologies. We searched PubMed, Scopus, Web of Science, and Embase for peer reviewed English language articles and synthesized evidence on polymer classes, processing routes, mechanical and chemical behavior, and clinical performance. Approximately 116 articles were included. Polymers remain central to clinical practice: poly methyl methacrylate (PMMA) is still widely used for dentures, high performance systems such as polyether ether ketone (PEEK) are expanding framework and implant-related indications, and resin composites and adhesives continue to evolve through nanofillers and bioactive formulations aimed at improved durability and reduced secondary caries. Thermoplastic polyurethane and copolyester systems drive clear aligner therapy, while polymer-based obturation materials and fiber-reinforced posts support endodontic rehabilitation. Additive manufacturing and computer aided design computer aided manufacturing (CAD CAM) enable customized prostheses and surgical guides, and sustainability trends are accelerating interest in biodegradable or recyclable dental polymers. Across domains, evidence remains heterogeneous and clinical translation depends on balancing strength, esthetics, biocompatibility, aging behavior, and workflow constraints. Full article

This study first heat-treats the surface of plain-woven carbon fibers to remove the surface sizing. The treated carbon fibers were then hot-pressed with polypropylene films to produce a carbon fiber/polypropylene prepreg. The resulting prepreg was subjected to uniaxial and off-axis tensile tests, providing fundamental data for constructing a constitute model for the carbon fiber/polypropylene prepreg. The relative error between the model predictions and experimental data is maintained within ±10%. Based on the experimental results, a temperature-dependent viscoelastic–hyperelastic constitutive model for carbon fiber/polypropylene is proposed. This model decomposes the unit volume strain energy function into four components: matrix isochoric deformation energy, fiber tensile strain energy, fiber–fiber shear strain energy, and fiber-matrix shear strain energy. The matrix energy is strain rate-dependent, exhibiting viscoelastic mechanical behavior. The material parameters of the constitutive model were identified by fitting the experimental data. The model was implemented in MATLABR2024a, and off-axis tensile tests were performed at temperatures ranging from 423 K to 453 K. Numerical simulations were compared with experimental results to validate the model. This work provides guidance for the development and validation of constitutive models for thermoplastic polypropylene prepregs. Full article

The presented study is focused on the evaluation of the mechanical and heat resistance performance of the polyester-based injection-molded components. For comparative purposes, we used a poly(ethylene terephthalate)/polycarbonate blend (PET/PC) and a poly(butylene terephthalate)/polycarbonate (PBT/PC) mixture, where both types of polymer blends were used as a matrix for different types of basalt fiber (BF)-reinforced composites. The investigated molding procedure consists of injection overmolding of the composite prepreg (insert). During the technological procedure, various material configurations were used, including overmolding with both unmodified blends and a composition with additional short basalt fibers. The results confirmed that the best balance of properties was obtained for complex parts reinforced with short BF and overmolded insert, where the tensile modulus can reach 8 GPa, while the impact strength was more than 30 kJ/m². The results of comparative tests indicate a significantly higher strength of overmolding joints for PET/PC-based materials. The relatively low heat deflection temp. (HDT) of around 70 °C after the injection molding procedure can be successfully improved by the annealing treatment, where the HDT can reach around 120 °C. The structural tests revealed that, besides some differences in crystallinity between the PET- and PBT-based blends, the thermomechanical performance of the manufactured composites is almost similar. It is worth pointing out the fundamental differences in the miscibility of the investigated blend systems, where for the PBT/PC mixture structural tests confirm the miscibility of polymer phases, while PET/PC particles are immiscible. Full article

The one-step hybrid forming process is a novel process to fabricate a metal fiber-reinforced plastic (FRP) structure with reduced cycle time and cost compared to classical multi-step methods. It is realized by a combined forming tool for both sheet metal and FRP forming to create a hybrid part in only one step. During the forming process, sheet metal pre-coated with an adhesion promoter is joined with the FRP simultaneously. In this work, the crashworthiness and lightweight potential of a hybrid crash management system manufactured with a hybrid forming process were investigated. It includes the experimental behaviors and finite element analysis of glass mat thermoplastics (GMT), as well as aluminum–GMT hybrid structures, under dynamic axial crushing loadings. Beginning with the original geometry of a series aluminum crash management system, the design was optimized for a hybrid forming process, where an aluminum sheet metal part is reinforced by a GMT structure with a ground layer and additional ribs. The forming behavior and fiber filling of the GMT crash box were determined and analyzed as well. Finite element method optimization was used to obtain the optimal geometry of the hybrid crash box with the highest possible specific energy absorption and the utmost homogeneous force level over displacement. A hybrid bumper beam was also developed, along with other necessary connection parts, to join the beam with the crash box and the entire crash management system (CMS) to the vehicle body. The joining technique was determined to be a key factor restricting the lightweight potential of the hybrid CMS. Full article

In this study, Fe₃O₄-chopped carbon fiber (CF) fillers with varying CF:Fe₃O₄ weight ratios (1:0.5, 1:0.75, and 1:1) were fabricated using the wet chemical reduction method. Different weight percentages (1, 3, 7 wt.%) of the CF/Fe₃O₄ fillers were used to fabricate lightweight, flexible, and porous thermoplastic polyurethane (p-TPU) composites for electromagnetic interference (EMI) shielding applications. Due to its poor electrical and magnetic properties, the TPU matrix alone exhibited negligible shielding effectiveness. The electromagnetic interference (EMI) performance of TPU composites is greatly affected by the amount of filler materials, the CF/Fe₃O₄ ratio, and the porous structure, which in turn influence the interfacial interactions between filler and p-TPU matrix. Effective electromagnetic attenuation is achieved by conductive CF network, interfacial polarization at CF/Fe₃O₄/TPU interfaces, and multiple internal reflections promoted by microstructural heterogeneity and porosity. A maximum EMI shielding effectiveness (SE_T) of 22.28 dB was achieved for a CF/Fe₃O₄/p-TPU composite with a filler load of 7 wt.%, a CF:Fe₃O₄ ratio of 1:1, and a porosity of 15%. Full article

This study addresses the issue of adapting the thermal drilling process for joining dissimilar thin-walled materials—sheets made of non-ferrous metal alloys and polymer composites with a thermoplastic matrix reinforced with glass and carbon fibers—without the use of connecting elements and without disrupting the continuity of the reinforcing fibers. An extensive metallographic study was conducted on bushings formed in thin metal sheets made of EN AW 6082 T6 aluminum alloy and AZ91 magnesium alloy obtained during separate drilling procedures. Experiments were also performed where the metal sheet and composite material overlapped, using both direct and sequential drilling above the melting point of the polymer matrix, applying various process parameters. The dimensions of the resulting bushings and the suitability of their profile for joining with composites were evaluated. The results suggest the possibility of joining metals and fiber composites through thermal drilling, and suitable joining process parameters and conditions are specified. To limit composite delamination, it is advisable to make a hem flange on the reverse side of the joints. CT scans confirmed the deflection of fibers around the hole in the composite without compromising their integrity. The load-bearing capacity of the joints and the possibility of creating hybrid mechanical–adhesive joints between these materials are the subject of Part Two of this study. Full article

Developing sustainable, high-performance biomass composites is crucial for replacing non-renewable structural materials. In this study, a “bamboo steel” composite was fabricated using a multilevel modification strategy involving alkali pretreatment, toughened resin impregnation, and surface functionalization. Bamboo fibers were treated to remove hemicellulose and lignin, enhancing porosity and interfacial bonding. The bamboo scaffold was subsequently impregnated with a thermo-plastic polyurethane-modified epoxy resin to create a robust, interpenetrating network. The optimized composite (treated at 80 °C) exhibited a flexural strength of 443.97 MPa and a tensile strength of 324.14 MPa, demonstrating exceptional stiffness and toughness. Furthermore, a superhydrophobic coating incorporating silica nanoparticles was applied, achieving a water contact angle exceeding 150° and excellent self-cleaning properties. This work presents a scalable strategy for producing bio-based structural materials that balance mechanical strength with environmental durability. Full article

This study investigates the Mode II fracture behavior of bamboo–coir–rubber (BCR) hybrid composite panels developed as sustainable alternatives for wood-based panels used in structural applications. The composites were fabricated using alternating bamboo and coir layers within a polypropylene (PP) thermoplastic matrix, with styrene–butadiene rubber (SBR) incorporated as an additive at 0–30 wt.% to enhance interlaminar toughness. Commercial structural plywood was tested as the benchmark. Mode II interlaminar fracture toughness (G_IIc) was evaluated using the ASTM D7905 End-Notched Flexure (ENF) test, supported by optical monitoring to study crack monitoring and Scanning Electron Microscopy (SEM) for microstructural interpretation. Results demonstrated a steady increase in G_IIc from 1.26 kJ/m² for unmodified laminates to a maximum of 1.98 kJ/m² at 30% SBR, representing a 60% improvement over the baseline and nearly double the toughness of plywood (0.7–0.9 kJ/m²). The optimum performance was obtained at 20–25 wt.% SBR, where the laminated retained approximately 85–90% of their initial flexural modulus while exhibiting enhanced energy absorption. Increasing the initial notch ratio (a₀/L) from 0.2 to 0.4 caused a reduction of 20% in G_IIc and a twofold rise in compliance, highlighting the geometric sensitivity of shear fracture to the remaining ligament. Analysis of Variance (ANOVA) confirmed that the increase in G_IIc for the 20–25% SBR laminates relative to plywood and the unmodified composite is significant at p < 0.05. SEM observations revealed rubber-particle cavitation, matrix shear yielding, and coir–fiber bridging as the dominant toughening mechanisms responsible for the transition from abrupt to stable delamination. The measured toughness levels (1.5–2.0 kJ/m²) position the BCR panels within the functional range required for reusable formwork, interior partitions, and transport flooring. The combination of renewable bamboo and coir with a thermoplastic PP matrix and rubber modification hence offers a formaldehyde-free alternative to conventional plywood for shear-dominated applications. Full article

In the context of increasing resource scarcity and environmental concerns, the development of green composite materials is essential for promoting sustainability in the automotive industry. However, poor interfacial compatibility between plant fibers and polypropylene (PP), as well as the performance deterioration under complex environmental aging conditions, severely limits their engineering applications. In this study, a synergistic interfacial modification strategy combining alkali treatment of hemp fibers (HFs) with polypropylene grafted maleic anhydride (PP-g-MAH) was employed to enhance fiber–matrix interaction. Hemp fiber-reinforced polypropylene composites (HFRPs) with varying fiber contents (7.5–30 wt%) were fabricated via injection molding. Accelerated aging tests were conducted on the compatibilized HFRPs for up to 2400 h under ultraviolet–thermal–moisture coupled conditions, in accordance with the SAE J2527 standard. The evolution of surface color, mechanical properties, chemical structure, and microstructure was systematically characterized. After aging, surface whitening of the composites was observed. Tensile strength and impact strength decreased by 9.57–22.12% and 38.68–46.03%, respectively, while flexural strength remained relatively stable due to the supporting effect of the fiber skeleton. The aging of compatibilized HFRPs follows an outside-in progressive degradation mechanism, characterized by a stepwise cascade of surface oxidation, crack propagation, moisture ingress, interfacial degradation, and mechanical performance deterioration. These findings offer valuable insights into the long-term durability of natural fiber-reinforced thermoplastic composites and provide theoretical and practical guidance for their structural design and application in demanding service environments. Full article

This study explores the potential of integrating thermoplastic surfaces into fiber-reinforced plastics (FRPs) to eliminate the need for extensive surface preparation prior to bonding. Traditional bonding techniques for FRPs, especially in aerospace applications, demand meticulous surface preparation to ensure adequate adhesion. As a potential alternative to conventional methods for generating adhesion, the formation of an interpenetrating polymer network (IPN) by diffusion of the epoxy monomers into a thermoplastic surface layer is investigated. The research involved manufacturing CFRP panels with thermoplastic surfaces, polyether sulfone (PES), and polyetherimide (PEI), followed by a bonding process with and without conventional surface preparation. The performance of the joints was tested by tensile shear and Mode-I fracture toughness tests and compared to reference samples without thermoplastic surfaces. The formation and characteristics of the IPNs were analyzed using optical microscopy, laser scanning microscopy, and energy-dispersive X-ray spectroscopy. The results demonstrate that PES surfaces, even without surface treatment, can provide high mechanical performance with shear strengths ranging from 18 MPa to 23 MPa. PEI surfaces led to a shear strength from 10 MPa up to 14 MPa, correlating to a less extensive IPN formation compared to PES. However, both thermoplastics significantly improved the bonding process performance without surface preparation. Full article

Lignin obtained in acidic conditions is a waste product in various technological processes like sulfite pulping, organosolv pulping, or bioethanol production. Knowing the structure of the lignin enables its use in high-value-added applications. In this paper, the lignin structure isolated from Pinus sylvestris L. and Populus deltoides × maximowiczii wood in acidic conditions was investigated. Two methods of lignin isolation (Klason method and a method using a sulfuric and phosphoric acid mixture) were compared. Additionally, lignin acetylation was performed. The lignin samples were analyzed using different instrumental techniques, such as size exclusion chromatography (SEC), attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), and scanning electron microscopy (SEM). Based on the studies carried out, it was found out that the lignin isolated from pine and poplar wood in acidic conditions had a highly condensed structure. This was evidenced by the high-weight average molar mass of lignin (up to 118,700 g/mol) and the precipitates, aggregates, and agglomerates on its surface. Moreover, the characteristic signals of condensed lignin in ATR-FTIR analysis (band with wavenumber of 767 cm⁻¹) and their decrease/disappearance (band that usually occurs with a wavenumber of about 814 cm⁻¹) were observed. Lignin acetylation and analysis in the 0.5% LiCl/DMAc system have proven particularly effective in the case of the condensed poplar lignin. The beneficial effect of lignin acetylation was confirmed by SEM analysis. The high-molecular-weight condensed lignin, despite some of its problematic properties connected mainly with solubility, is a valuable substance that can be used for different applications (carbon fibers or as an additive for thermoplastic blends), which was confirmed by the studies in this paper and the findings of other scientists. Full article

In this work, microfibrillated cellulose (MFC) from ash branch wood was used as reinforcement in a thermoplastic starch matrix to develop environmentally friendly materials. Pulp fibers and MFCs were characterized by SEM, TEM, and FTIR. Corn starch biofilms were prepared via casting, formulating eight biofilms with 5 and 10 wt% of MFC. Also, extracts of Muicle and Hibiscus were added to incorporate antibacterial properties. The biofilms were evaluated for mechanical, thermal, and antibacterial properties. Also, properties such as color, opacity, morphology, electrical conductivity, contact angle, and solubility, among others, were evaluated. The reinforced biofilms were homogeneous, dimensionally stable, and transparent with slight color changes. MFC incorporation enhanced hydrogen bonding, which increased the ultimate tensile strength from 11.2 MPa to approximately 19–21 MPa and the Young’s modulus from 809 MPa to 1034–1192 MPa. The presence of MFC also reduced solubility from 48.7% to 38.7–39.8% and decreased water vapor permeability by about 20–23% in biofilms with 10 wt% MFC. Gas barrier properties and the glass transition temperature depended on extract type and fiber content, indicating greater rigidity. The use of ash-based MFC encourages the implementation of circular economy strategies and the development of sustainable biocomposites. Full article

Thin-walled cellular structures of continuous fiber-reinforced thermoplastic composites (CFRTPCs) have received much attention from both academics and industry due to their superior properties. Additive manufacturing provides an efficient solution for fabricating these thin-walled cellular structures of CFRTPCs. However, the process often requires cutting fiber filaments at jumping points during printing. Furthermore, the filament may twist, fold, and break due to sharp turns in the printing path. These issues adversely affect the mechanical properties of the additive manufactured part. In this paper, a Euler graph-based path planning method for additive manufacturing of CFRTPCs is proposed to avoid jumping and sharp turns. Euler graphs are constructed from non-Eulerian graphs using the method of doubled edges. An optimized Hierholzer’s algorithm with pseudo-intersections is proposed to generate printing paths that satisfy the continuity, non-crossing, and avoid most of the sharp turns. The average turning angle was reduced by up to $20.88\%$ and the number of turning angles less than or equal to $120°$ increased by up to $26.67\%$ using optimized Hierholzer’s algorithm. In addition, the generated paths were verified by house-made robot-assisted additive manufacturing equipment. Full article

In an interlayered carbon fiber reinforced polycarbonate (CFRPC) composite constructed of nine CF plies alternating between ten PC sheets, designated [PC]₁₀[CF]₉, applying homogeneous low voltage electron beam irradiation (HLEBI) at 200 kV cathode potential, with V_c setting at a 43.2 kGy dose, to both finished sample surfaces resulted in a 47% increase in Charpy impact strength and a_uc at median fracture probability (P_f) of 0.50 over that of untreated, from 118 kJm⁻² to 173 kJm⁻². Increasingly higher V_c settings of 150, 175, and 200 kV successively increased a_uc at median-P_f of 0.50 to 128, 155, and 173 kJm⁻², respectively. Strengthening is attributed to increasing the HLEBI penetration depth, D_th, into the sample thickness. Since the [PC]₁₀[CF]₉ has an inhomogeneous structure, D_th is calculated for each ply successively into the thickness. Scanning electron microscopy (SEM) photos showed a hierarchy of fracture mechanisms from poor PC/CF adhesion in untreated; to sporadic PC adhesion with aggregated CF at 150 kV; to high consolidation of CFs by PC at 200 kV. X-ray photoelectron spectroscopy (XPS) examination of the CF surface in the fracture area showed C1s carbonate O–(C=O)–O and ester O–(C=O)–R peak generation at 289 to 292 eV to be non-existent in untreated; well-defined at 150 kV; and increased in intensity at 200 kV, after which a reduction was observed at 225 kV. Moreover, the 200 kV yielded the largest area sp³ peak at 49.5%, signifying an increase in graphitic edge planes in the CF, apparently as dangling bonds, for increased adhesion sites to PC. For O1s scan, 200 kV yielded the largest area O–(C=O)–O peak at 34%, indicating maximum PC adhesion to CF. At the higher 225 kV, increase in a_uc at P_f of 0.50 was less, to 149 kJm⁻², and XPS indicated a lower amount of O–(C=O)–O groups, apparently by excess bond severing by the higher V_c setting. Full article

During the manufacturing and development of a proof-of-concept prototype of a continuous fiber polyphenylene sulfide (PPS) composite vehicle component, unexpected results were observed in thick laminates of an E-glass-fiber-reinforced PPS matrix, which utilized carbon black as a colorant (GF/PPS+CB). Extensive interlaminar macrocracking, transverse intralaminar microcracking, and micro-/macrovoids were observed in GF/PPS+CB laminates after compression forming. When processed under identical conditions, no micro-/macrocracking or voids were present in GF/PPS laminates and carbon fiber/PPS laminates without carbon black colorant. These observations prompted further investigation into the influence of processing conditions, presence of colorant, mold design (open and closed molds), and geometry (flat and curved) on the development of matrix defects in thick continuous fiber-reinforced PPS laminates. Full article