Search Results (126)

The effects of ultraviolet (UV) light and moisture environments on the properties of continuous fiber-reinforced thermoplastic composites were investigated in this study. Materials included carbon fiber-reinforced polyphenylene sulfide (CF/PPS), glass fiber-reinforced polyphenylene sulfide (GF/PPS), glass fiber-reinforced polypropylene (GF/PP), and glass fiber-reinforced polyethylene terephthalate (GF/PET). Fiber orientation was noted to affect the response of the materials to UV and moisture environments. For CF/PPS, UV exposure led to enhanced unidirectional tensile and flexure properties, and quasi-isotropic compression strength, but reduced in-plane shear properties of cross-ply laminates and the short-beam shear strength of unidirectional laminates. Exposure to moisture had minimal effect on CF/PPS laminates. UV light caused a slight decrease in tensile strength and strain of unidirectional samples of GF/PPS and a slight increase in these properties with various degrees in quasi-isotropic samples. Exposure to moisture was noted to cause a reduction in most of the mechanical properties with various degrees in unidirectional and quasi-isotropic GF/PPS laminates. For GF/PP, exposure to UV and moisture decreased the tensile and compressive strengths of unidirectional and quasi-isotropic laminates. However, a notable increase in flexure strength was observed in both laminates after UV exposure. The GF/PET quasi-isotropic laminates showed reduced tension, compression, and flexure strengths but increased impact resistance and short-beam strength under UV exposure, while moisture decreased in-plane shear properties of cross-ply laminates and increased the glass transition temperature of unidirectional laminates. Vertical burn and surface flammability and smoke generation tests showed high flame resistance of CF/PPS and GF/PPS composites, and less so for GF/PP and GF/PET composites. The findings highlight the various responses of the materials to extreme environments. Full article

Material extrusion additive manufacturing, commonly implemented as fused deposition modeling (FDM) or fused filament fabrication (FFF), has evolved into a manufacturing route for reinforced thermoplastic composites, including particle-filled, short-fiber-reinforced, and continuous-fiber-reinforced systems. The process is governed by a layer-by-layer thermal cycle. Deposited roads cool rapidly, are repeatedly reheated by subsequent material deposition, and finally cool non-uniformly as part of the growing structure. This thermal history generates residual-stress that may cause warpage, build–platform detachment, delamination, dimensional error, and reduced mechanical performance. This review synthesizes residual-stress formation, measurement, modeling, parameter effects, and mitigation in material-extruded reinforced thermoplastic composites, with emphasis on short and continuous-fiber systems. Stress formation is discussed in terms of constrained thermal contraction, crystallization shrinkage, anisotropic stiffness, fiber-constrained deformation, porosity, and fiber–matrix thermal expansion mismatch. Experimental methods, including hole drilling, layer removal, curvature methods, embedded fiber Bragg gratings, digital image correlation, photoelasticity, and warpage metrology, are critically compared for anisotropic and porous printed composites. Analytical and numerical models are reviewed from layerwise shrinkage formulations to crystallization-coupled thermo-viscoelastic finite element simulations. Finally, mitigation strategies are evaluated. A central conclusion is that reinforcement can suppress visible distortion while increasing stress retained in a stiffer structure. Therefore, warpage alone is not a sufficient residual stress metric. Full article

Carbon fiber-reinforced thermoplastic composites (CFRTPs) have attracted increasing attention in aerospace, transportation, marine engineering, and other advanced manufacturing fields owing to their high specific mechanical properties, impact resistance, weldability, reprocessibility, and potential recyclability. However, the high melt viscosity of thermoplastic matrices, the permeability limitations associated with different reinforcement architectures, and the chemical inertness of carbon fiber surfaces continue to restrict resin impregnation, interfacial bonding, defect control, and forming stability. This review systematically summarizes recent advances in CFRTP manufacturing from the perspective of material-derived processing challenges and interface engineering. First, representative thermoplastic matrix systems and reinforcement architectures are discussed, with emphasis on their effects on processability, crystallization behavior, resin flow, and load transfer. Subsequently, six major forming processes, including hot stamping, injection molding, pultrusion, filament winding, automated fiber placement, and additive manufacturing, are critically compared in terms of processing principles, typical defects, technical limitations, and application boundaries. Particular attention is given to process-induced quality issues such as voids, wrinkling, springback, fiber breakage, warpage, insufficient consolidation, and weak interlayer bonding. Finally, interface engineering strategies, including chemical surface modification, interfacial structural design, and functional interlayer design, are reviewed as practical routes to improve wetting, shorten impregnation pathways, and enhance fiber–matrix load transfer in high-viscosity thermoplastic systems. This review highlights that CFRTP manufacturing should be understood as a coupled materials–processing–interface problem rather than a single forming operation. Future development is discussed with emphasis on reproducible manufacturing, processability-oriented materials, scalable interface engineering, predictive modeling, and standardized structural validation. Full article

Recycled thermoplastics offer a promising route for valorizing industrial residues and developing thermoplastic-bonded wood-based panels without added formaldehyde-based resins. In this study, experimental wood–polymer composite boards were produced from recycled acrylonitrile–butadiene–styrene (ABS) edge-banding waste used as the polymer matrix and industrial wood fibers used as the lignocellulosic reinforcement. The boards were manufactured at target densities of 800–1200 kg·m⁻³ and wood fiber contents of 10–30%, followed by the evaluation of selected physical and mechanical properties, including water absorption, thickness swelling, modulus of elasticity and bending strength. Thermogravimetric analysis of the recycled ABS edge-banding material and qualitative optical microscopy of the board surfaces were used to support, but not independently prove, the interpretation of the composite structure. The recycled ABS waste enabled the formation of compact boards, with density exerting the strongest influence on water resistance and bending performance. The regression models indicated a balanced region at 21.84 wt.% wood fibers and 1134 kg·m⁻³, corresponding to predicted water absorption of 1.62%, thickness swelling of 3.22%, modulus of elasticity of 2931 N·mm⁻² and bending strength of 22.20 N·mm⁻². Optical microscopy suggested a more continuous ABS-rich surface in the most homogeneous specimens, whereas local accumulations of fine particles and areas of limited polymer coverage were observed on the opposite surface. These findings demonstrate the potential of recycled ABS edge-banding waste for wood–polymer board production, while indicating that additional feedstock cleaning and sieving should be investigated in subsequent work to improve furnish uniformity and structural homogeneity. Full article

Fused deposition modeling (FDM) provides a flexible manufacturing route for continuous fiber-reinforced thermoplastic composites, but weak interlaminar bonding and the trade-off between load-bearing capacity and deformation capability still limit their structural applications. In this study, multi-scale carbon/Kevlar fiber hybridization was introduced into acrylonitrile butadiene styrene (ABS)-based composites by combining continuous carbon fiber (CCF) or continuous Kevlar fiber (CKF) with short carbon fiber-filled ABS (ABS/SCF) or short Kevlar fiber-filled ABS (ABS/SKF). Four hybrid configurations and two continuous-fiber baseline composites were fabricated by FDM and evaluated through three-point bending tests, floating roller peel tests, peeled-surface SEM observations, and Rule-of-Mixtures-based hybrid effect analysis. The flexural results showed that short-fiber-filled matrices improved the flexural properties of both CCF- and CKF-based composites, but the degree of improvement depended on the fiber combination. Among the investigated configurations, CCF + ABS/SCF exhibited the highest flexural modulus and strength, which were 34.31% and 27.26% higher than those of CCF + ABS, respectively. For the CKF-based composites, CKF + ABS/SCF increased the flexural modulus and strength by 31.51% and 26.78%, compared with CKF + ABS, while maintaining the progressive deformation behavior associated with Kevlar reinforcement. The peel results showed that all hybrid composites had higher interlaminar peel resistance than their corresponding baselines, with increases ranging from 18.66% to 54.42%. The peeled-surface SEM observations indicated that the short-fiber-filled matrices changed the crack-propagation features, with more matrix tearing, fiber pull-out, and irregular peeling areas. The RoM-based comparison showed that the measured flexural properties of all hybrid configurations were higher than the corresponding RoM reference values. Overall, CCF + ABS/SCF was more suitable for improving stiffness and load-bearing capacity, whereas CKF + ABS/SCF showed a more balanced response in terms of flexural performance, interlaminar peel resistance, and progressive deformation behavior. Full article

There is a lack of knowledge concerning the interlaminar fracture toughness of 3D-printed composite materials using both commercial filament composites and fused deposition modeling (FDM) technology from Markforged^®. In this investigation, additive manufacturing (AM) continuous fiber-reinforced thermoplastic (cFRT) specimens have been tested to characterize the initiation and propagation of interlaminar fracture toughness in mode I (G_I). Unidirectional glass fiber (GF)-reinforced polyamide 6 (PA) laminates were characterized by means of the double cantilever beam (DCB) test. These specimens were manufactured using a MarkTwo^® printer and tested without doublers, following a laminate configuration selected according to appropriate experimental findings reported in the state of the art, ensuring reliable fracture characterization. The experimental results exhibited repeatability and strong agreement between the modified compliance calibration (MCC) and modified beam theory (MBT) reduction methods. The resistance curve (R-curve) indicated a progressive increase in fracture resistance during crack propagation. To analyze the experienced failure mechanism during testing, the fracture surfaces of representative post-mortem DCB specimens were observed using a scanning electron microscope (SEM), revealing characteristic morphological features at two magnification levels. Moreover, representative cross-sections of the tested DCB specimens were electronically observed to analyze the interlaminar morphologies, showing an irregular and random distribution of the matrix, fiber, and voids between consecutive plies and adjacent deposited rasters. Compared with previously reported Markforged^® continuous fiber-reinforced systems, the GF/PA composite material exhibited intermediate initiation fracture toughness but lower propagation toughness. This study contributes to filling the existing gap in fracture toughness data for glass fiber-reinforced additively manufactured composites. Full article

This study evaluates the industrial-scale feasibility of injection moulding of a recycled polypropylene composite reinforced with recycled fibers derived from an industrial waste stream. Although previous laboratory-scale research has demonstrated the potential of natural fiber-reinforced thermoplastics, their large-scale industrial implementation remains limited due to uncertainties related to processability, reproducibility, and manufacturing robustness. In this work, the composite material is validated through injection moulding trials carried out in four independent industrial companies located in Andalusia (Spain) and three industrial case studies across different industrial sectors in Slovenia, operating under real production conditions. The extrusion process was characterized in terms of process stability, confirming continuous operation with automated dosing and stable material flow without interruptions under industrial conditions. Injection processing parameters, cycle stability, part quality, and defect formations are also considered important when assessing the manufacturing feasibility. The multi-site validation approach enables the evaluation of reproducibility across different injection moulding systems and mould geometries, providing critical insights into the scalability and technological readiness level of recycled natural fiber-reinforced polypropylene composites. Although direct energy consumption measurements were not systematically recorded, the observed processing stability and cycle repeatability indicate a consistent and energy-efficient operation under industrial processing conditions. The results contribute to bridging the gap between laboratory-scale material development and real industrial implementation. Full article

Thermoplastic composite resistance welding boasts stable process, low cost and reliable quality, making it a dependable joining technique for such materials. This process employs a heating element (HE) as the sole heat source and therefore, it is critical in controlling the welding process. This study proposed a perforated stainless-steel mesh (SSM) as the HE and investigated the effect of welding parameters and insulation film thickness on the joint performance of resistance welded carbon-fiber-reinforced polyamide 6 (CF/PA6). The results showed that the joint lap shear strength (LSS) increased first then decreased as the welding pressure, welding time and welding current increased. The maximum LSS reached 24.4 MPa when 0.2-mm-thick films were used. The joint failure mode was identified as blocky fiber peeling with compromised fiber continuity for the joints welded with 0.1-mm-thick and 0.3 mm-thick PA6 films. For the joints made with 0.2-mm-thick PA6 films, the joint failure mode was characterized by resin peeling from the fiber surface. Full article

Continuous unidirectional (UD) thermoplastic composite tapes are increasingly used in aerospace, automotive, and energy applications because of their high specific strength, low weight, recyclability, and compatibility with automated manufacturing. Since final component performance strongly depends on tape quality, reliable defect characterization and detection are essential. In this study, manufacturing-induced defects in polypropylene-based UD tapes reinforced with carbon and glass fibers were investigated using real images acquired directly from laboratory-scale production without synthetic data. Defects related to interfacial integrity, matrix distribution, fiber architecture, and surface irregularities were systematically analyzed, and a practical four-class defect taxonomy was established. To enable automated inspection under limited-data conditions, lightweight YOLOv8, YOLOv11, and the new YOLO26 models were comparatively evaluated using a UD tape-specific augmentation strategy combining physically constrained Albumentations and on-the-fly augmentation. Among the tested models, YOLO26-s achieved the best overall performance, reaching a mean mAP@0.5 of 0.87 ± 0.03, outperforming YOLOv11 (0.83) and YOLOv8 (0.78), with 0.90 precision and 0.85 recall. Interfacial (0.92 mAP) and matrix-related (0.90 mAP) defects were detected most reliably, whereas fiber-related (0.89 mAP) and surface defects (0.79 mAP) remained more challenging, particularly in glass-fiber-reinforced tapes due to transparency-masking effects. The results demonstrate the potential of compact deep learning models for computationally efficient and manufacturing-relevant in-line quality monitoring of UD tape production. Full article

This study investigates the machinability of Continuous Fiber-Reinforced Thermoplastic Composite (CFRTP) produced via Material Extrusion (MEX) additive manufacturing, focusing on drilling as a critical post-processing step in hybrid manufacturing. CFRTP components, fabricated from 3K carbon fibers and a PLA matrix, were subjected to systematic drilling tests under varying cutting speeds (50–110 m/min) and feed rates (0.06–0.24 mm/rev). Thrust force (Fz) and torque (Mz) were recorded using a high-precision dynamometer to evaluate the influence of cutting parameters on mechanical loads and damage mechanisms. Results indicate that increasing the feed rate significantly increases Fz and Mz, promoting fiber pull-out, delamination, and edge deformation, particularly at hole entry and exit regions. Conversely, higher cutting speeds reduce Fz and Mz due to thermal softening of the PLA matrix, enabling more controlled fiber–matrix interaction. Microscopic analyses revealed that damage severity correlates strongly with mechanical load levels. While high feed rates caused pronounced surface irregularities and matrix smearing, low feed rates combined with high cutting speeds yielded smoother hole morphology and preserved fiber–matrix integrity. The study concludes that optimal drilling conditions for CFRTP materials involve low feed rates and high cutting speeds, minimizing mechanical loads and suppressing damage formation. These findings provide a scientific basis for precision finishing strategies in hybrid manufacturing, enhancing dimensional accuracy and structural reliability of CFRTP components for advanced engineering applications. Full article

Thermoplastic carbon fiber-reinforced polymer (CFRP) composites possess the intrinsic capability to heal delamination and matrix cracks via thermal re-melting. However, under impact loading, they are prone to severe fiber fracture, which significantly compromises their repairability. To address this, this study introduced polytetrafluoroethylene (PTFE) films as pre-set interlaminar defects within continuous carbon fiber-reinforced polyamide 6 (CF/PA6) thermoplastic cross-ply laminates. Low-velocity impact tests were conducted at varying energy levels to comparatively investigate the impact response and damage mechanisms of the CFRPs with and without embedded defects. Experimental results indicate that the embedded interlaminar defects triggered a transition in the failure mode of the CFRP from brittle fracture to progressive damage behavior. Compared to the baseline laminates, the specimens with embedded defects maintained higher flexural stiffness under low-energy impact. Furthermore, they effectively reduced the extent of fiber breakage by dissipating impact kinetic energy through extensive delamination, interlaminar frictional sliding, and plastic micro-deformation. These findings verify the feasibility of achieving macroscopic pseudo-ductility through interlaminar microstructural tailoring. This research provides an experimental basis and methodological support for the pseudo-ductile design of thermoplastic composites. Full article

Compared to reinforcing concrete with steel bars, rebars—made of fiber-reinforced plastic—have a high potential for resource savings in the construction industry due to their corrosion resistance. For the large-volume market of reinforcement elements, efficient manufacturing processes must be developed to ensure the best possible bond behavior between concrete and rebar. In contrast to established FRP-rebars made with thermosetting materials, the use of a thermoplastic matrix enables surface profiling without severing the edge fibers as well as subsequent bending of the bar. The rebars to be produced in this study are based on the process of reactive thermoplastic pultrusion of continuously glass fiber reinforced aPA6. Their surface must enable a mechanical interlocking between the reinforcement bar and concrete. Concepts for a profiling device have been methodically developed and evaluated. The resulting concept of a double wheel embossing unit with a variable infeed and an infrared preheating section is built as a prototype, implemented in a pultrusion line, and further optimized. For a comprehensive understanding of the embossing process, reinforcement bars are manufactured, characterized, and evaluated under parameter variation according to a statistical experimental plan. The present study demonstrates the relationship between the infeed, preheating temperature, and haul-off speed with respect to the embossing depth, which is equivalent to the rib height. No degradation of the Young’s modulus was observed as a result of the profiling process. Full article

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 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

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