Search Results (94)

Natural-fiber-reinforced polypropylene (PP) composites are gaining increasing interest as lightweight, sustainable alternatives for various packaging and applications. This study investigates the effect of filler addition sequence on the mechanical, morphological, thermal, and dynamic mechanical properties of PP-based composites reinforced with graphite nanoplatelets (GnP) and kenaf fiber (KF). Two filler incorporation sequences were evaluated: GnP/KF/PP (GnP initially mixed with KF before PP addition) and GnP/PP/KF (KF added after mixing GnP with PP). The GnP/KF/PP composite exhibited superior mechanical properties, with tensile strength and flexural strength increasing by up to 25% compared to the control, while GnP/PP/KF showed a 13% improvement. SEM analyses revealed that initial mixing of GnP with KF significantly improved filler dispersion and interfacial bonding, enhancing stress transfer within the composite. XRD and DSC analyses showed reduced crystallinity and lower crystallization temperatures in the addition of KF due to restricted polymer chain mobility. Thermal stability assessed by TGA indicated minimal differences between the composites regardless of filler sequence. DMA results demonstrated a significantly higher storage modulus and enhanced elastic response in the addition of KF, alongside a slight decrease in glass transition temperature (T_g). The results emphasize the importance of optimizing filler addition sequences to enhance mechanical performance, confirming the potential of these composites in sustainable packaging and structural automotive applications. Full article

Natural composites find application in various fields because of their low specific weight and low investment cost. But due to their inherent nature, natural composites have lower strength and tend to absorb moisture, which makes them weak. In this work, woven glass, mono-bi-filament polypropylene, and polyester fibers in an epoxy matrix were developed with four and five different stacking layers of texture utilizing the hand-layup procedure. However, understanding the directional dependence of material properties is necessary for the application of these new materials. Three distinctive plates were fabricated for the purpose of the investigation. The laminated plates were tested on a universal testing machine (UTM) and a flexible test setup to examine the mechanical properties of the polymer fiber. By adding short fibers such as polypropylene, polyester fibers in a random manner improved the mechanical strength of the polymer composite compared to the other fiber types such as woven glass fiber sheets and woven polypropylene sheets placed in the middle of the composite. This is because short polymer fibers bond well with epoxy resin and have very good bonding strength. Full article

Glass fiber reinforced polypropylene composite plates have gradually attracted more attention because of their repeated molding, higher toughness, higher durability, and fatigue resistance compared to glass fiber reinforced thermosetting composites. In practical engineering applications, composite plates have to undergo bending effect at different angles in corrosive environment of concrete, including bending bars from 0~90°, and stirrups of 90°, which may lead to long-term performance degradation. Therefore, it is important to evaluate the long-term performance of glass fiber reinforced polypropylene composite bending plates in an alkali environment. In the current paper, a new bending device is developed to prepare glass fiber reinforced polypropylene bending plates with the bending angles of 60° and 90°. It should be pointed out that the above two bending angles are simulated typical bending bars and stirrups, respectively. The plate is immersed in the alkali solution environment for up to 90 days for long-term exposure. Mechanical properties (tensile properties and shear properties), thermal properties (dynamic mechanical properties and thermogravimetric analysis) and micro-morphology analysis (surface morphology analysis) were systematically designed to evaluate the influence mechanism of bending angle and alkali solution immersion on the long-term mechanical properties. The results show the bending effect leads to the continuous failure of fibers, and the outer fibers break under tension, and the inner fibers buckle under compression, resulting in debonding of the fiber–matrix interface. Alkali solution (OH⁻ ions) corrode the surface of glass fiber to form soluble silicate, which is proved by the mass fraction of glass fiber decreased obviously from 79.9% to 73.65% from thermogravimetric analysis. This contributes to the highest degradation ratio of tensile strength was 71.6% (60° bending) and 65.6% (90° bending), respectively, compared to the plate with bending angles of 0°. A high curvature bending angle (such as 90°) leads to local buckling of fibers and plastic deformation of the matrix, forming microcracks and fiber–resin interface bonding at the bending area, which accelerates the chemical erosion and debonding process in the interface area, bringing about an additional maximum 10.56% degradation rate of the shear strength. In addition, the alkali immersion leads to the obvious degradation of storage modulus and thermal decomposition temperature of composite plate. Compared with the other works on the long-term mechanical properties of glass fiber reinforced polypropylene, it can be found that the long-term performance of glass fiber reinforced polypropylene composites is controlled by the corrosive media type, bending angle and immersion time. The research results will provide durability data for glass fiber reinforced polypropylene composites used in concrete as stirrups. Full article

The global construction industry faces pressing challenges in enhancing building energy efficiency standards. To address this critical issue, facilitate worldwide green and low-carbon transformation in construction practices and improve the thermal performance of building wall panels to achieve optimal levels, a novel polypropylene fiber-reinforced concrete wall panel has been developed and investigated. A three-dimensional steady-state heat transfer finite element model of the wall panel was established to simulate its thermal performance. Key parameters, including the thickness of the inner and outer concrete layers, insulation layer thickness, connector spacing, and connector arrangement patterns, were analyzed to evaluate the thermal performance of the fiber-reinforced concrete composite sandwich wall panel. The results indicate that the heat transfer coefficients of the G-FCSP and FCSP wall panels were 0.768 W/m² · K and 0.767 W/m² · K, respectively, suggesting that the glass fiber grid had a negligible impact on the thermal performance of the panels. The embedded insulation layer was crucial for enhancing the thermal insulation performance of the wall panel, effectively preventing heat exchange between the two sides. Increasing the thickness of the concrete layers had a very limited effect on reducing the heat transfer coefficient. Reducing the spacing of the connectors improved the load-bearing capacity of the composite wall panel to some extent but had minimal influence on the heat transfer coefficient; to achieve optimal performance by balancing structural load distribution and thermal damage resistance, a connector spacing ranging from 200 mm to 500 mm is recommended. The variation in heat transfer coefficients among the four different connector arrangement patterns demonstrated that reducing the thermal conduction media within the wall panel should be prioritized while ensuring mechanical performance. It is also recommended that the connectors are arranged in a continuous layout. Full article

This study investigates the long-term mechanical performance of highly reinforced long glass fiber thermoplastic polypropylene composites, focusing on the effects of processing parameters, fiber length, and skin–core structures. Dynamic mechanical and creep analyses were conducted to evaluate the impact of injection molding on the final microstructure and long-term mechanical properties. The findings confirm that a significant microstructural change occurs at a fiber length of 1000 µm, which strongly influences the material’s mechanical behavior. Samples with fiber lengths above this threshold reveal greater creep resistance due to the reduced flowability that leads to more entangled, three-dimensional fiber networks in the core. This structure limits chain mobility and consequently improves the resistance to long-term deformation under load. Conversely, fiber lengths below 1000 µm promote a planar arrangement of fibers, which enhances chain relaxation, fiber orientation, and creep strain. Specifically, samples with fiber lengths exceeding 1000 µm exhibited up to a 15% lower creep strain compared to shorter fiber samples. Additionally, a direct relationship is observed between the findings in the viscoelastic response and quasi-static tensile properties from previous studies. Finally, the impact of the microstructure is more pronounced at low temperatures and becomes nearly negligible at high temperatures, indicating that beyond the glass transition temperature, the microstructural effect diminishes gradually until it becomes almost non-existent. Full article

Enhancing the damping capacity of concrete structures is crucial for improving their resilience under dynamic loading conditions such as earthquakes, vehicular impacts, and industrial vibrations. This study presents a comprehensive review of how material properties—specifically fiber reinforcement, ductility, and toughness—affect the damping behavior of concrete. Various types of fiber reinforcements, including steel, polypropylene, and glass fibers, are analyzed in terms of their contribution to energy dissipation mechanisms such as crack bridging, fiber pullout, and frictional sliding. The role of the ductility index and toughness in augmenting the damping ratio is also discussed, demonstrating that higher ductility and toughness directly correlate with enhanced energy dissipation. Furthermore, the interrelationships between material properties and structural performance under cyclic loading are critically evaluated. The findings highlight that optimizing fiber content and improving the mechanical properties of concrete can significantly increase its damping capacity, thereby offering strategic pathways for designing safer and more durable infrastructure, especially in seismic-prone regions. This review aims to consolidate the current understanding and provide recommendations for future research focused on developing high-damping concrete composites. Full article

This study investigates the influence of various reinforcing fibers, including coconut, basalt, glass, merino wool, and polypropylene, on the properties and processability of cementitious mixtures, with a particular emphasis on their application in 3D printing. The incorporation of fibers at a concentration of 1 wt.% was found to significantly hinder the printing process. Specifically, certain fibers, such as polypropylene, rendered extrusion impractical due to nozzle clogging. However, reducing the fiber content to 0.5 wt.% improved material flowability and minimized structural defects during printing. Fiber selection, in addition to its impact on mechanical properties, plays a crucial role in determining overall process efficiency. Mixtures incorporating coal slag as a dense filler, combined with stiff fibers such as basalt or glass, exhibited the highest flexural strength. Moreover, the inclusion of merino wool fibers enhanced the flexural performance of fly ash-based mixtures, achieving strength levels comparable to or exceeding those of stiffer fibers. These findings contribute to the advancement of sustainable construction practices. Notably, samples produced via 3D printing consistently demonstrated higher flexural strength than those fabricated using traditional molding techniques. This enhancement is attributed to microstructural modifications induced by the layer-by-layer deposition process. Depending on the sample composition and the type of reinforcing fiber, water absorption behavior varied significantly. Merino wool and coconut fibers exhibited the highest water absorption due to their hydrophilic nature and capillary action, particularly in 3D-printed samples with open-pore structures. In contrast, glass and basalt fibers, characterized by their higher density and hydrophobicity, exhibited lower water absorption levels. These results underscore the importance of optimizing fiber type, concentration, and processing methodologies to achieve tailored performance in fiber-reinforced cementitious mixtures. Such optimizations align with the principles of sustainable development and hold significant potential for advancing 3D-printed construction applications Full article

Short fiber-reinforced thermoplastic composites (SFRTPs) have excellent recyclability and processability, but their mechanical properties are weak compared to continuous fiber products. Various studies have reported that the addition of GNPs improves the mechanical properties of SFRTPs, but it is unclear what effect different types of reinforcing fibers have on a hybrid composite system. In this study, the effect of adding a small amount (1 wt%) of graphene nanoplatelets (GNPs) to fiber-reinforced polypropylene composites on their mechanical properties was investigated from a crystallinity perspective. GNPs were mixed with polypropylene (PP)/carbon fiber (CF) or PP/glass fiber (GF) using a melt blending process, and composites were molded by injection molding. The results of mechanical property characterization showed no significant effect when GNPs were added to PP/CF, but when GNPs were added to PP/GF, this increased the composite’s tensile strength and Young’s modulus by approximately 20% and 10%, respectively. The interfacial shear strength (IFSS) predicted using the modified Kelly–Tyson equation did not change much before and after the addition of GNPs to PP/CF. On the other hand, the IFSS increased from 10.8 MPa to 19.2 MPa with the addition of GNPs to PP/GF. The increase in IFSS led to an increase in the tensile strength of PP/GF with the incorporation of GNPs. Differential scanning calorimetry (DSC) indicated that GNPs accelerated the crystallization rate, and the X-ray diffraction (XRD) results confirmed that GNPs acted as a crystal nucleating agent. However, CF was also shown to be a nucleating agent, limiting the effect of GNP addition. In other words, it can be said that the addition of GNPs to PP/GF is more effective than their addition to PP/CF due to the differential crystallization effects of each fiber. Full article

Composite pipe fittings with an outer layer of 20% long glass fiber-reinforced polypropylene (LGFR-PP) and an inner layer of polypropylene (PP) were prepared via water-powered projectile-assisted co-injection molding short-shot (W-PACIM-S), water-powered projectile-assisted co-injection molding overflow (W-PACIM-O), gas-powered projectile-assisted co-injection molding short-shot (G-PACIM-S), and gas-powered projectile-assisted co-injection molding overflow (G-PACIM-O)techniques. The effects of different injection molding processes on the wall thickness, inner surface roughness, glass fiber orientation, and pressure resistance of pipe fittings were studied to evaluate the quality of the pipe fittings formed by each process. Compared with the short-shot method, the overflow method results in pipes with thinner walls in each layer, a more uniform distribution, smoother inner wall surfaces, and better orientation of glass fibers along the axial direction in the near boundary layer, resulting in better pressure resistance. Under the same injection method, the difference in fluid medium did not significantly change the trend of wall thickness variation in each layer. However, compared with gas, high-pressure water improves the uniformity of the pipe wall thickness and inner wall quality. In addition, the introduction of the warhead is more conducive to improving the degree of glass fiber orientation of the pipe fittings, and the thickness of the residual wall thickness of the pipe fittings has a great influence on the pressure resistance of the pipe fittings. Full article

Reflective thermal insulation layers can offer an energy-efficient strategy for preventing temperature rises by reflecting sunlight on surfaces. Our previous study presented a novel solvent-based method to prepare porous polypropylene (PP) with high solar reflectivity. However, the stiffness and strength of the neat porous PP were insufficient for thermal insulation applications, as mechanical loads from installation and environmental factors limit the applicability of such products. This paper addresses this gap by applying our solvent-based surface modification technology to glass fiber (GF)-reinforced PP composite sheets, creating a previously unexplored system. While the enhanced modulus and strength aligned with expectations, the micro- and nano-structured porous outer layers situated below the skin layer of the sheets, the refractive index mismatch between the PP matrix and the GF, and the size of the GF delivered a notable advancement in reflective thermal insulation performance. The combined effect of 30 wt% GF, nucleating agents, and surface modification resulted in a highly porous surface layer featuring spherulite sizes of 0.5–2.0 μm. With these combined effects, we achieved a modulus value of ~4 GPa, a tensile strength of 60 MPa, and an average solar reflectance of up to 94%. Thermal insulation performance measurements demonstrated that the registered inner temperature was lower by 24.1 °C compared to neat PP sheets. These combined effects demonstrate the potential of our solvent-based surface modification technology to develop cost-effective, porous PP composite sheets for efficient reflective thermal insulation. Full article

In recent years, wind energy has emerged as one of the fastest-growing green technologies globally, with projections indicating that decommissioned wind turbine blades (WTBs) will accumulate to millions of tons by the 2030s. Due to their thermosetting nature and high glass/carbon fiber content, the efficient recycling of WTBs remains a challenge. In this study, we utilized solid-state shear milling (S3M) to produce a fine WTB powder, which then underwent surface modification with a silane coupling agent (KH550), and we subsequently fabricated WTB-reinforced polypropylene (PP) composites with enhanced mechanical performance through solid-state stretching. The stretching-process-induced orientation of the PP molecular chains and glass fibers led to orientation-induced crystallization of PP and significant improvements in the mechanical properties of the PP/WTB@550 composites. With 30 wt. % WTB content, the PP/WTB@550 composite achieved a tensile strength of 142.61 MPa and a Young’s modulus of 3991.19 MPa at a solid-state stretching temperature of 110 °C and a stretching ratio of 3, representing increases of 268% and 471%, respectively, compared to the unstretched sample. This work offers both theoretical insights and experimental evidence supporting the high-value recycling and reuse of WTBs through a cost-effective, environmentally friendly, and scalable approach. Due to the enhanced mechanical properties of the PP/WTB composite and the intrinsic waterproofing and corrosion resistance of PP, it is hoped that such a composite would be used in road engineering and building materials, such as geogrids, wall panels, floor boards, and floor tiles. Full article

Filament winding is a widely used out-of-autoclave manufacturing technique for producing continuous fiber-reinforced thermoplastic composites. This study focuses on optimizing key filament winding process parameters, including heater temperature, roller pressure, and winding speed, to produce thermoplastic composites. Using Box–Behnken response surface methodology (RSM), the study investigates the effects of these parameters on the compressive load of glass fiber-reinforced polypropylene (GF/PP) and polyphenylene sulfide (GF/PPS) composite cylinders. Mathematical models were developed to quantify the impact of each parameter and optimal processing conditions were identified across a wide temperature range, enhancing both manufacturing efficiency and the overall quality of the composites. This study demonstrates the potential of thermoplastic filament winding as a cost-effective and time-efficient alternative to conventional methods, addressing the growing demand for lightweight, high-performance, out-of-autoclave composites in industries such as aerospace, automotive, and energy. The optimized process significantly improved the performance and reliability of filament winding for various thermoplastic applications, offering potential benefits for industrial, aerospace, and other advanced sectors. The results indicate that GF/PPS composites achieved a compressive load of 3356.99 N, whereas GF/PP composites reached 2946.04 N under optimized conditions. It was also revealed that operating at elevated temperatures and reduced pressure levels enhances the quality of GF/PPS composites, while for GF/PP composites, maintaining lower temperature and pressure values is crucial for maximizing strength. Full article

In order to efficiently utilize industrial solid waste while minimizing the preparation cost of engineering materials and the technical difficulty of construction, this paper prepared a high fly ash content alkali-activated fly ash slag composite system at normal temperatures and conducted an in-depth investigation on it. A systematic study was conducted on the workability, mechanical properties, and microstructures of the alkali-activated fly ash slag pastes, including setting times, strength, phase, and molecular structures. We then designed and prepared fiber-reinforced alkali-activated fly ash slag mortar and studied the effects of the alkali activator modulus, glass fiber (GF), and polypropylene fiber (PPF) on the workability, mechanical properties, and frost resistance of the mortar. The following main conclusions were drawn: By adjusting the modulus of alkali activator for alkali-activated fly ash slag pastes, characteristics that meet engineering requirements could be obtained. The compressive strength of the pastes decreased with increasing proportions of fly ash, and it first increased and then decreased with increases in the activator modulus. The flexural strength decreased to varying degrees as the modulus of the activator increased. Through SEM, fly ash particles with different reaction degrees could be observed, indicating that the reaction was still ongoing. The addition of GF and PPF reduced the fluidity of mortar and significantly improved its strength and frost resistance. Fiber had the most significant effect on improving the strength of the mortar, as an activator modulus of 1.0. 0.45% PPF increased the flexural and compressive strength of the mortar by 14.33% and 29.1%, respectively, while 0.90% GF increased the flexural and compressive strength of the mortar by 3.12% and 19.21%, respectively. The frost resistance of the mortar with an activator modulus of 1.0 was significantly better than that of the mortar with an activator modulus of 1.4. 0.45% PPF and reduced the quality loss rate of the mortar by 49.30%, effectively delaying the deterioration of its freeze-thaw performance. Full article

In this study, the thermoforming formability of continuous glass fiber-reinforced polypropylene (CGFRPP) laminates below the melting temperature were investigated. The forming limits of CGFRPP laminates were explored using flexural tests, Erichsen tests and deep drawing tests. The failure mechanism of CGFRPP in thermoforming was investigated by observing typical failure specimens using a microscope. The results show that the flexural performance and Erichsen performance are optimal at 130 °C and 2 mm/min. At 160 °C and 100 mm/min, the deep drawing performance is optimal. The restriction of fibers by the matrix is affected by the deformation temperature, and the creation of defects is affected by the deformation rate. During forming, the CGFRPP laminates undergo shear and extrusion deformations, resulting in wrinkles, delamination, and fiber aggregation. Full article

Thermoplastic composites are gaining widespread application in aerospace and other industries due to their superior durability, excellent damage resistance, and recyclability compared to thermosetting materials. This study aims to enhance the lap shear strength (LSS) of resistance-welded GF/PP (glass fiber-reinforced polypropylene) thermoplastic composites by modifying stainless steel mesh (SSM) heating elements using a silane coupling agent. The influence of oxidation temperature, solvent properties, and solution pH on the LSS of the welded joints was systematically evaluated. Furthermore, scanning electron microscopy (SEM) was utilized to investigate the SSM surface and assess improvements in interfacial adhesion. The findings indicate that surface treatment promotes increased resin infiltration into the SSM, thereby enhancing the LSS of the resistance-welded joints. Treatment under optimal conditions (500 °C, ethanol solvent, and pH 11) improved LSS by 27.2% compared to untreated joints. Full article