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In the current study, a novel radical‐induced cationic frontal polymerization (RICFP) concept capable of rapid curing at room temperature via visible light irradiation is represented. Initially, the optimal formulation, which can be most effectively cured with visible light irradiation, is determined based on thickness, hardness, curing speed, and mechanical properties using FT‐IR, DSC, TGA, and flexural test methods. Subsequently, the viability of the method is illustrated by fabricating glass fiber‐reinforced composites through the hand lay‐up technique, employing the optimized formulation and glass fibers in various forms (chopped strand mat and biaxial). Mechanical properties of the obtained composites, including bending, tensile, and shear tests, are carried out according to relevant international standards and compared with reference composites thermally cured with amine‐based hardener by conventional method. [ABSTRACT FROM AUTHOR]

The present investigation targets the physical, mechanical, and thermal characteristics of glass fabric‐reinforced vinyl ester/polyester hybrid laminates filled with ferrous, nickel, and tungsten micro‐particles. The metal‐fillers‐glass fabric reinforced vinyl ester/polyester hybrid composites was produced by distributing 1 wt% ferrous, nickel, and tungsten with an ultrasonication probe‐assisted wet layup method. Polyester resin reinforced with glass fabrics and tungsten fillers (PRGT) presents improved mechanical characteristics compared with other hybrid laminates, with tensile, compression, and flexural strength values of 157.89 MPa, 163.74 MPa, and 167.29 MPa, respectively. The fractographic microstructure of tensile fracture PRGT laminates exhibits that glass fibers pull out, microcracks, and lower gaps, because of stronger filler‐fabric‐matrix adhesion when compared with other hybrid laminates. The artificial neural network modeling was conducted to choose the best composite among the various manufactured composites. Statistical analysis was observed from the one‐way ANOVA technique, substantiating that the physical, mechanical, and thermal characteristics of metal fillers‐reinforced hybrid composites were statistically significant. Highlights: Metal‐fillers‐glass fabric reinforced vinyl ester/polyester hybrid composites.Selection of the best composite from developed composites by ANN.Tungsten fillers are a useful material for reinforcement. [ABSTRACT FROM AUTHOR]

Short glass fibers are generally used in posterior dental restorations to enhance the mechanical properties and improve the material microstructure. Two resin-based composites (S0 and SF) were formulated and characterized to investigate the influence of zirconium in their characteristics and properties. The organic part of the investigated materials was the same (BisGMA, TEGDMA, and a photochemical polymerization system), and in the inorganic part, besides quart, glassA, and hydroxylapatite with Zn, sample S0 contained strontium glass with zirconium and sample SF contained fiber powder of chopped zirconium. The samples were characterized by the degree of conversion (DC), mechanical properties, water sorption (WS), scanning electron microscopy (SEM), atomic force microscopy (AFM) before and after the WS test, and antimicrobial properties. The results obtained were subjected to one-way ANOVA and Tukey's statistical tests. Both samples had a high DC. Regarding the mechanical properties, both samples were very similar, except DTS, which was higher for the composite without fibers. After 14 days, the WS value of the SF sample was lower than that of the S0 sample. Water caused significant changes in the topography of the SF sample, but thanks to its antimicrobial properties and the diffusion phenomenon, SF had a more pronounced antimicrobial effect. This study shows that the addition of appropriate amounts of Sr-Zr-glass powder gives the material in which it is added similar properties to material containing chopped zirconium glass fiber powder. According to the antimicrobial test results, resin composites containing experimental zirconia fillings can be considered in future in vitro clinical studies for posterior reconstructions with significantly improved mechanical properties. [ABSTRACT FROM AUTHOR]

The use of adhesively bonded joints between composite panels, metal panels, or between composites and metals are used in the aerospace and automotive industries to avoid stress concentrations due to fasteners while reducing weight. Quantifying the bond thickness allows for confidence that loading is being properly transferred. This study presents a methodology to measure bondline thickness using the data obtained from an immersion quality ultrasound scan using an out‐of‐tank, field‐portable, utlrasonic testing (UT) scanner. Eighteen bonded coupons were fabricated using a paste‐type adhesive filling a range of gaps between substrates of 0.254 and 1.27 mm. Three adhesively bonded coupon types were investigated: carbon fiber laminates, fiber glass laminates, and aluminum plates. A semiautomated algorithm is presented to quantify bondline thickness from the ultrasound data for each coupon type, generating a spatially varying 3D point cloud of adhesive thickness. Bondline measurements obtained using ultrasound are then validated over two orthogonal planes against measurements taken from x‐ray computed tomography reconstructions. Results indicate a typical accuracy of 0.081 mm for bondline thickness quantification for all samples studied, with the results from the inspection of the composite coupons yielding an error of 0.078 mm, whereas the accuracy when scanning the aluminum coupons yielded an error of 0.086 mm. Highlights: Field‐portable, inspection station is presented for full waveform ultrasonics.Mathematical procedure to characterize adhesive bondline thickness.Results are presented for a variety of material systems and adhesive thicknesses.Results are validated against x‐ray computed tomography with a typical accuracy of 0.081 mm. [ABSTRACT FROM AUTHOR]

Glass fibers (GFs) are frequently employed as reinforcement fibers for polymer resins such as epoxy and polyester. The mechanical behaviors of GFs polymer composites are nevertheless constrained by weak interfacial adhesion between polymer matrix and GFs. Herein, we invented a cross‐linking modified sizing agent using polyethyleneimine and bisphenol A epoxy emulsion, and studied the effect of cross‐linking extent on GF surface characteristics and GF/epoxy interfacial adhesion. The treatment of GFs with cross‐linking modified sizing agent facilitated the formation of interpenetrating polymer networks in composites for strengthening interface interaction. The results show that the modified GFs have a rough surface and improved interfacial adhesion with epoxy matrix. When sizing agents with cross‐linking extent of the 23.0%, the GF/epoxy composites show advanced interfacial shear strength (IFSS) and transverse fiber bundle tension (TFBT) strength. This work demonstrates that the cross‐linking extent of sizing agent could regulate interfacial adhesion, which is a facile and promising strategy in reinforcing glass fiber polymer composites. Highlights: Crosslink the sizing agent to enhance GF mechanical properties was reported.GF surface energy was enhanced and thickness of GF/epoxy interphase increased.IFSS and TFBT strength of the GF/resin composites increased by 23.65% and 30.54%, respectively. [ABSTRACT FROM AUTHOR]

To investigate the real anchorage performance of basalt and glass hybrid fiber reinforced plastic (FRP) anchors in external corrosive environments. In this paper, a combination of experimental studies and finite element analysis was used. By carrying out pull‐out tests of basalt and glass hybrid FRP anchors under the synergistic effect of freeze–thaw cycles and alkaline environment, the effects of factors such as hole diameter, anchorage length, and mortar strength on their anchorage performance and durability were investigated. Critical corrosion time was introduced to determine the degree of corrosion of the anchor rods. After that, it combined with numerical simulation to reveal the degradation mechanism of the anchorage performance of hybrid anchors. The results showed that the best anchorage performance of basalt/glass hybrid FRP anchors was achieved when the hole diameter was 24 mm, the anchorage length was 175 mm, and the mortar strength was 45.5 MPa. The ultimate pull‐out load was up to 122.16 kN. When the time did not exceed the critical corrosion time, the ultimate load‐carrying capacity of basalt and glass hybrid FRP anchors increased by 9.3% compared to the uncorroded environment. Beyond the critical corrosion time, the ultimate load‐carrying capacity was reduced by 23.3% and the anchorage performance was degraded. In addition, the contact interface between the anchor and the mortar is the weak area of the anchoring structure, which should be focused on in the later design of the actual project. Highlights: Basalt/glass hybrid FRP anchors have good corrosion resistance.The anchoring performance of hybrid FRP anchors under the coupled environment is studied.Hole diameter and anchoring length have more influence on the anchor performance.The concept of critical corrosion time is put forward.The failure mechanism and coupling environment influence are revealed by FES. [ABSTRACT FROM AUTHOR]

Nowadays, additive manufacturing techniques such as the Fused Filament Fabrication appear to be among the most promising methods for enabling modern industry to produce components of high geometrical complexity. The main characteristic of this method is the deposition of thermoplastic polymers that can be further reinforced with chopped and/or continuous fibers that attribute to the product some unique structural characteristics. Nevertheless, the process is susceptible to a variety of defects that are derived from the fabrication process parameters, such as porosity, insufficient fiber impregnation with the polymer and fiber disorientation. On the other hand, since the applicability of the process depends on the development of numerical tools for assessing the effects of these defects, the accurate detection and quantification of them is a crucial part of it. In the present work, these defects are studied experimentally by implementing an X-ray computed tomography testing campaign. The manufacturing defects are identified using well-established techniques while a complete analysis of the distribution of porosity is presented for various zones of Onyx, Onyx/Carbon and Onyx/Glass fiber reinforced structures. Finally, the tendency of the overall pore content to increase with increasing number of continuous fiber reinforcement was identified as well as porosity variations in printing direction are presented. [ABSTRACT FROM AUTHOR]

This study presents a comparison of the self-healing ability of two types of thermosetting polymer composites based on unsaturated polyester resin as a matrix. The first type contains hollow glass-fiber fabric as a healing agent carrier. In the second type, microcapsules made of urea-formaldehyde condensation, containing a healing agent were introduced. In both cases butanediol diglycidyl ether was used as a healing agent. The kinetics of the healing process of studied polymer composites was estimated via alteration of Young and shear moduli (G') during a time, using ultrasonic defectoscopy. It was found that the healing process of the micro-cracks made in the volume of composites was complete in 5 hours. [ABSTRACT FROM AUTHOR]

Frontal polymerization (FP) has attracted increasing interest in recent years in various applications. This polymerization method can be very promising for the polymerization of thick materials with high fillers content in the range of 50–80% (weight) by local application of a reasonable amount of energy. In this work, recent advances in controllable and predictive behavior for photoinduced frontal photopolymerization are reported. Here, tert‐butyl peroxybenzoate (Luperox‐P) is selected to initiate thermal polymerization at depth because its high polymerization ability and its decomposition temperature is in a promising range, i.e., neither extremely high (monomer decomposition) nor very low (storage stability issues). Thermal imaging experiments are used to follow the temperatures in the samples in real time. The number of cured layers and the depth of cure are also determined. This paper investigates various factors such as the contents of both photo and thermal initiators, the light intensity, the fiber contents, the irradiation time, etc., resulting in a statistical design of experiments with the factors: 1) content of Luperox P and 2) the irradiation time used to investigate the influence on photoinduced frontal polymerization. Markedly, FP appears to be fully controllable for a storage‐stable, tunable 1K system. [ABSTRACT FROM AUTHOR]

This study aims to analyze strength properties and low-cycle dynamic tests of composite materials modified with glass and basalt fibers. Biopolyamide 4.10 was used as the matrix, and the fiber contents were 15, 30, and 50% by weight. Static tensile tests, impact tests, and determination of mechanical hysteresis loops were carried out as strength tests. The length of the fibers in the produced composites and their processing properties were determined. The composite materials were compared with commercially available glass fiber-reinforced composites with 30 and 50% fiber contents. The results showed that such composites can successfully replace composite materials based on petroleum-based polymeric materials, providing high strength properties and reducing the negative environmental impact by using renewable sources. Composites with 30% basalt fiber composition were characterized by higher tensile strength by about 60% compared to commercially available composites with 30% glass fiber composition and an almost doubly increased Young's modulus. Increasing the content of basalt fibers to 50% results in a further increase in strength properties. Despite the lower tensile strength compared to polyamide 6 with 50% glass fiber content, basalt fibers provided an approximately 10% higher modulus of elasticity. [ABSTRACT FROM AUTHOR]

Lightweighting of automotives is crucial for the decrease of fuel and energy consumption, as well as CO2 emission and environmental pollution. Polymer composites, especially the high strength glass fiber/polyamide (GF/PA) composites, have great potential in lightweight; however, they have not been universally accepted due to their insufficient performance. Here, a stearate‐ended hyperbranched polyester (HBP‐12‐n) is designed and high‐performance GF/PA6 composites with high GF content are prepared. The flowability of the composites can be further increased by combining carboxyl‐ended hyperbranched polymer (HyPer C181) with HBP‐12‐n. Compared with unmodified GF/PA6 composites, the melt flow index (MFI) can be increased remarkably to 587% by adding a 0.7 wt% mixture of HBP‐12‐75 and HyPer C181, and the strength and toughness remain competitive. The simultaneous improvement in MFI and impact strength of GF/PA6 composites is the first discovery of this kind, and a synergistic mechanism of amphiphilic bridging‐deformation slipping‐interfacial strengthening of hyperbranched polymers is proposed to account for this phenomenon. This work provides a simple strategy to fabricate GF/PA6 composites with the extensive application for automotive parts and has great prospects in making automotives lightweight and reduction of CO2 emissions. [ABSTRACT FROM AUTHOR]

Poly (phenylene sulfide) (PPS) is a super engineering plastic that has not only excellent rigidity and high chemical resistance but also excellent electrical insulation properties; therefore, it can be applied as an electronic cover or an overheating prevention component. This plastic has been extensively applied in the manufacture of capacitor housing as, in addition to being a functional and lightweight material, it has a safety feature that can block the electrical connection between the electrolyte inside and outside the capacitor. Moreover, the fabrication of PPS composites with high glass fiber (GF) content facilitates the development of lightweight and excellent future materials, which widens the scope of the application of this polymer. However, the crystallinity and mechanical properties of PPS/GF composites have been found to vary depending on the cooling temperature. Although extensive studies have been conducted on the influence of cooling temperature on the crystalline behavior of PPS-based composites, there has been limited research focused particularly on PPS/GF composites for capacitor housing applications. In this study, to apply PPS/GF composites as film capacitor housings, specimens were prepared via injection molding at different cooling temperatures to investigate the composites' tensile, flexural, and impact energy absorption properties resulting in increases in mechanical properties at high cooling mold temperature. Fracture surface analysis was also performed on the fractured specimens after the impact test to confirm the orientation of the GF and the shape of the micropores. Finally, the crystallinity of the composites increased with higher cooling temperatures due to the extended crystallization time. [ABSTRACT FROM AUTHOR]

Polymer composites have remarkable popularity in the aerospace and automotive industries due to their high strength-to-weight ratio and ease of production. In this study, the effects of the glass fiber (GF) and maleic anhydride grafted polypropylene (PP-g-MA) as coupling agent on mechanical properties, shrinkage and warpage of polypropylene (PP) were investigated. Tensile, flexural, shrinkage and warpage tests were performed according to relevant standards. Results indicate that the strengths and moduli of composite specimens have been significantly improved compared to pure PP. Also, the shrinkage and warpage of composite specimens were reduced. Analysis of variance showed that both GF and PP-g-MA had a significant effect. In composite with a 40% weight fraction of GF, the tensile and flexural strengths were increased by 91% and 62%, respectively. A micromechanics model was proposed to predict the tensile modulus of composites. A good agreement between experiments and the model was achieved. [ABSTRACT FROM AUTHOR]

Fiber reinforced plastics (FRP) offer huge potentials for energy efficient applications. Special care must be taken during both FRP fabrication and usage to ensure intended material properties and behavior. This paper presents a novel approach for the monitoring of the strain and temperature of glass fibre reinforced polymer (GFRP) materials in the context of both production process monitoring and structural health monitoring (SHM) applications. The sensor is designed to be integrated into GFRPs during the production process, and the sensor concept includes possibilities of automated placement during textile layup. To minimize sensor impact on GFRP integrity and to simplify vacuum setup and part handling, the sensor operates without the need for either wires or a battery. In the first sections of this work, sensor concept, design and prototype fabrication are presented. Subsequently, it is shown how the sensors can be used for flow front monitoring and cure estimation during GFRP production by measuring local resin temperature. The resulting specimens are then characterized regarding strain measurement capabilities, mechanical influence on the host component and overall system limitations. Average strain sensor accuracy is found to be ≤0.06 mm/m, while a maximum operation temperature of 126.9 °C and a maximum reading distance of 38 mm are measured. Based on a limited number of bending tests, no negative influence of sensor presence on breaking strength could be found. Possible applications include structural components, e.g., wind turbine blades or boat hulls. [ABSTRACT FROM AUTHOR]

For commercial civil applications of laminated composite material, characterizations to forecast the interlaminar shear behavior and viscoelastic response across a wide temperature range are essential. In this study, the interlaminar shear strength (ILSS) of glass/epoxy (GE) composites dispersed with binary nanofillers nanosilica‐multilayer graphene (NS‐MLG) and nanosilica‐nanoclay (NS‐NC) was analyzed at an in‐situ testing temperature of 20, 70, and 110°C. Further, the viscoelastic property of the composites was studied using a dynamic mechanical thermal analyzer (DMTA) in the temperature range of 35–165°C. An increase in the ILSS value of around 9% and 10% was observed at room temperature for GE/MLG‐NS and GE/NC‐NS, respectively, compared to control GE composites. In contrast, the trend was seen to change at higher temperatures. There was a slight decrement in the storage modulus (E′) of GE/MLG‐NS and GE/NC‐NS composites in the glassy region compared to control GE composites. The mean Tg of the GE composite (control) was nearly 107.3°C when the E′ decline onset temperature was taken into account, but after the addition of MLG‐NS, it was 10.1°C below. The mean Tg of GE/NC‐NS was determined to be 106.3°C, and in the glass transition as well as rubbery regions, it was observed to compete with the E′ value of the control GE composites. Fractography was done using micrographs obtained from environmental scanning electron microscope (ESEM). Traces of polymeric material found at the fiber surface certified the improved interfacial adhesion between glass fiber and polymer in the matrix‐modified composite samples. [ABSTRACT FROM AUTHOR]

With industrialization and population growth, solid waste management has become a universal challenge. The destination and incorrect storage of the waste from quarries have become a recurring problem caused by the extraction of mineral resources. The possibility of use for this waste, to minimize its impacts, is the creation of new products that can be useful to engineering using stone powder. Therefore, this study aims to create a new composite using limestone powder with different granulometry to analyze the influence that its insertion and the grain size can cause in these materials. The produced laminates were submitted to uniaxial tensile tests under the norm ASTM D 3039 and volumetric density ASTM D 792, The modifications that occurred in the properties of the specimens were studied in detail, obtaining results that show that the insertion of limestone powder provides the material with new mechanical characteristics, such as the rigidity increase. Among the produced composites, the one that had received limestone as obtained presented the best performance, increasing 9.33% of its elasticity modulus in comparison to the original. [ABSTRACT FROM AUTHOR]

In this study, carbon nanotubes (CNTs) were grown under the same conditions as those of carbon fibers and glass fibers, and a comparative analysis was performed to confirm the potential of glass fibers with grown CNTs as electromagnetic interference (EMI) shielding materials. The CNTs were grown directly on the two fiber surfaces by a chemical vapor deposition process, with the aid of Ni particles loaded on them via a Ni-P plating process followed by heat treatment. The morphology and structural characteristics of the carbon and glass fibers with grown CNTs were analyzed using scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDS), X-ray diffraction (XRD), and X-ray photoelectron spectrometry (XPS), and the EMI shielding efficiency (EMI SE) of the directly grown CNT/carbon and glass fiber-reinforced epoxy matrix composites was determined using a vector-network analyzer. As the plating time increased, a plating layer serving as a catalyst formed on the fiber surface, confirming the growth of numerous nanowire-shaped CNTs. The average EMI SET values of the carbon fiber-reinforced plastic (CFRP) and glass fiber-reinforced plastic (GFRP) with grown CNTs maximized at approximately 81 and 40 dB, respectively. Carbon fibers with grown CNTs exhibited a significantly higher EMI SET value than the glass fiber-based sample, but the latter showed a higher EMI SET increase rate. This indicates that low-cost, high-quality EMI-shielding materials can be developed through the growth of CNTs on the surface of glass fibers. [ABSTRACT FROM AUTHOR]

Purpose: Direct ink writing (DIW) is a robust additive manufacturing technology for the fabrication of fiber-reinforced thermoset composites. However, this technique is currently limited to low design complexity and minimal heights. This study aims to investigate the feasibility of UV-assisted DIW of composites to enhance the green-part strength of the printed inks and resolve the complexity and the height limitations of DIW technology. Design/methodology/approach: The experimental approach involved the preparation of the thermoset inks that are composed of nanoclay, epoxy, photopolymer and glass fiber reinforcement. Composite specimens were fabricated in complex geometries from these ink feedstocks using UV-assisted, hybrid 3D-printing technology. Fabricated specimens were characterized using optical microscopy, three-point bending mechanical tests and numerical simulations. Findings: The introduced hybrid, UV-assisted 3D-printing technology allowed the fabrication of tall and overhanging thermoset composite structures up to 30% glass fiber reinforcement without sagging during or after printing. Glass fiber reinforcement tremendously enhanced the mechanical performance of the composites. UV-curable resin addition led to a reduction in strength (approximately 15%) compared to composites fabricated without UV resin. However, this reduction can be eliminated by increasing the glass fiber content within the hybrid thermoset composite. Numerical simulations indicate that the fiber orientation significantly affects the mechanical performance of the printed composites. Originality/value: This study showed that the fabrication of high-performing thermoset composites in complex geometries was possible via hybrid DIW technology. This new technology will tremendously expand the application envelope of the additively manufactured thermoset composites and the fabrication of large composite structures with high mechanical performance and dimensional freedom will benefit various engineering fields including the fields of aerospace, automotive and marine engineering. [ABSTRACT FROM AUTHOR]

The melt strength of Elium® acrylic resin is an important factor to ensure limited fluid flow during welding. To provide Elium® with a suitable melt strength via a slight crosslink, this study examines the effect of two dimethacrylates, namely butanediol-di-methacrylate (BDDMA) and tricyclo-decane-dimethanol-di-methacrylate (TCDDMDA), on the weldability of acrylic-based glass fibre composites. The resin system impregnating a five-layer woven glass preform is a mixture of Elium® acrylic resin, an initiator, and each of the multifunctional methacrylate monomers in the range of 0 to 2 parts per hundred resin (phr). Composite plates are manufactured by vacuum infusion (VI) at an ambient temperature and welded by using the infrared (IR) welding technique. The mechanical thermal analysis of the composites containing multifunctional methacrylate monomers higher than 0.25 phr shows a very little strain for the temperature range of 50 °C to 220 °C. The quantity of 0.25 phr of both of the multifunctional methacrylate monomers in the Elium® matrix improves the maximum bound shear strength of the weld by 50% compared to those compositions without the multifunctional methacrylate monomers. [ABSTRACT FROM AUTHOR]

Moisture absorption in composites significantly influence the fiber/matrix interface regions and mechanical properties. Hence, it is very important to quantify the moisture storage in interfaces and correlate it to the mechanical behavior. The novelty of this article is that, for the first time, it explores the correlation of moisture absorption parameters with the mechanical behavior of composites. The paper studies four different types of moisture‐soaked composites—glass fiber/epoxy, carbon fiber/epoxy, ZnO nanowire incorporated glass fiber/epoxy, and ZnO nanowire incorporated carbon fiber/epoxy. One‐dimensional hindered diffusion model (1D HDM) was used for the extraction of moisture absorption parameters. The hindrance coefficient (ratio of bound to unbound moisture) of composites was found to increase proportionately with the increase in the volume of interfacial regions. Only in carbon fiber/epoxy composite, it did not increase proportionately due to the relatively larger degradation of interface. This was correlated well with mechanical test responses wherein carbon fiber/epoxy exhibited anomalous failure modes due to relatively larger degradation of interface. Numerical simulations were also carried out to describe the moisture absorption in composites. Numerical simulations of moisture absorption in composites using time‐varying boundary conditions matched very well with experimental as well as 1D HDM results. [ABSTRACT FROM AUTHOR]

Fiber-reinforced composites, such as carbon and glass fibers, are widely used across various industries. This is mainly a result of their outperforming properties in contrast with traditional materials. As a response to the environmental legal enforcement of the recycling of composite materials, several recycling methods such as mechanical, thermal, and chemical recycling, have been developed. Despite various merits, these recycling methods still face challenges, such as the heterogeneity of material, the quality of the recycled product, the high cost of recycling, and a lack of an established market. Since, in many cases, the financial aspect tends to be the major barrier to recycling composites, the appropriate cost modelling of the recycling process requires urgent consideration. To the knowledge of the authors, there is no prior research efforts on the reviewing of cost modelling techniques on composites recycling. Cost modelling research projects for different recycling technologies, with their findings and limitations, are sought from the literature and reported in this paper. It is found that recycling techniques still cannot compete with traditional landfilling in terms of cost, and are dependent on fiber recovery rates and plant capacities. Following a comprehensive literature review, research gaps are identified to formulate the research directions in this field. [ABSTRACT FROM AUTHOR]

In recent years, various new and practical products have emerged thanks to rapidly developing science and technology to meet human needs and expectations. A variety of these products are new materials known as composites. The use of composites is also increasing, from the aircraft industry to the automobile industry, to other areas such as sports equipment, infrastructures. The goal of this research is to present a hybrid composite material that can be retainable and does not harm the environment that can be used in the automobile industry. This goal has been tried to be achieved by using natural fiber (flax fabric) reinforced glass fibers in different weights (86 gr/m² and 100 gr/m²). The vacuum assisted resin transfer molding (VARTM) system was used to fabricate the composite samples. Composite products produced during the study were tested with regard to mechanical (tensile strength, bending strength), hardness, and morphological (scanning electron microscopy). The results indicate that the tensile strength value of hybrid composites is 2.5 times and 1.7 times higher than that of homogeneous composites and flexural test results also 78% and 23% enhancement compared to single fiber composites. According to the hardness test measurement of hybrid composites, it was found that the hardness value changed with an increase of 14% and 33% compared to the homogeneous composite. Scanning Electron microscopy (SEM) analysis images also coincide with mechanical analysis results. The hybrid composites produced in the study have become a favorable option in diverse areas of use in the automotive industry, considering human health and environmental factors. [ABSTRACT FROM AUTHOR]

The article presents the results of dynamic crushing of sandwich tubes that had skins made of carbon or glass fibers – with epoxy resin – and an I214 poplar ply core. By increasing the number of poplar plies from two to six, the absorbed energy is doubled, showing the significant contribution of the wood. The Specific Energy Absorption of sandwiches with carbon fiber skins oscillated between 49.4 J/g and 60 J/g while that with glass fiber skins varied from 35.4 to 43.3 J/g. [ABSTRACT FROM AUTHOR]

We herein report the influences of glass fibers (GFs) on the thermal stability and long-term mechanical performance at elevated temperatures of thermotropic liquid crystal polyester (TLCP) composites for advanced applications in the industrial sectors of automotive, electric/electronics, aerospace, and construction. For this purpose, TLCP-based composites with 10–40 wt% GF loadings are fabricated by facile melt-mixing and injection-molding. The scanning electron microscopy (SEM) images and X-ray diffraction patterns demonstrate that the GFs are dispersed in the TLCP matrix with a microfibrillar structure. The specific interactions between TLCP and GFs in the composites are identified by ATR FT-IR spectroscopic analyses. The thermal degradation temperatures of the composites increase slightly with the increment of GFs with high thermal stability and heat capacity. The long-term mechanical durability of TLCP/GF composites at 150 °C is analyzed by obtaining time-dependent storage modulus master curves based on the stepped isothermal method and time–temperature superposition principle. The dynamic mechanical moduli, activation energy, and long-term mechanical durability are found to be highly enhanced for TLCP composites with higher GF loadings, which is owing to the efficient stress transfer from the TLCP matrix to reinforcing GF fillers via specific interactions at the composite interface. [ABSTRACT FROM AUTHOR]

Flame retardancy properties of neat PLA can be improved with different phosphorus-based flame retardants (FRs), however, developing flame retardant PLA-based engineering composites with maintained mechanical performance is still a challenge. This study proposes symbiosis approaches to enhance the flame retardancy behavior of polylactide (PLA) composites with 20 wt% short glass fibers (GF). This was first implemented by exploring the effects of various phosphorus-based FRs up to 5 wt% in neat PLA samples. Among the used phosphorus-based FRs, the use of only 3 wt% of diphosphoric acid-based FR (P/N), melamine coated ammonium polyphosphate (APPcoated), and APP with melamine synergist (APP/Mel) resulted in achieving the V0 value in a vertical burning test in the neat PLA samples. In addition to their superior efficiency in improving the flame retardancy of neat PLA, P/N had the least negative effect on the final mechanical performance of PLA samples. When incorporated in PLA composites with 20 wt% GF, however, even with the use of 30 wt% P/N, the V0 value could not be obtained due to the candlewick effect. To resolve this issue, the synergistic effect of P/N and aromatic polycarbodiimide (PCDI) cross-linker or Joncryl epoxy-based chain-extender (CE) on the flame retardancy characteristics of composites was examined. Due to the further chain modification, which also enhances the melt strength of PLA, the dripping of composites in the vertical burning test terminated and the V0 value could be reached when using only 1 wt% PCDI or CE. According to the scanning electron microscopic analysis, the use of noted chain modifiers further homogenized the distribution and refined the particle size of P/N within the PLA matrix. Hence this could synergistically contribute to the enhancements of the fire resistance performance of the PLA composites. Such incorporation of P/N and chain modifiers further leads to the enhancement of the mechanical performance of PLA composites and hence the resultant product can be proposed as a promising durable bioplastic engineering product where fire risk exists. [ABSTRACT FROM AUTHOR]

Slender footbridges are prone to excessive vibrations due to pedestrian effects, and comfort criteria often govern their design. In this sense, composite materials that combine high damping capacity with relatively high stiffness and low mass can provide functional benefits. This paper presents a study of the dynamic behaviour of an 11 m long hybrid footbridge made of two I‐shaped pultruded glass fibre reinforced polymer (GFRP) main girders and a thin steel fibre reinforced self‐compacting concrete (SFRSCC) deck, in operation since 2015. The main goals were (i) to improve the knowledge of the dynamic properties of composite footbridges and (ii) to assess the benefits of using a structure made of pultruded GFRP instead of a conventional material (steel), namely, considering its greater ability to dissipate energy. The resonant frequencies, damping ratios, and mode shapes of the footbridge were identified based on experimental testing. A finite element (FE) model of the footbridge was developed and calibrated with test data and used to simulate the effects of pedestrian loads. Simulations of the same type were conducted on an equivalent structural system made of steel profiles. The simulation results of the two short‐span footbridges with similar natural frequencies enhance the impact of high‐order harmonics of the pedestrian load in the dynamic response. It is also shown that polymer‐based components can contribute to limiting vibrations in footbridges or even act as self‐dampers. [ABSTRACT FROM AUTHOR]

Design and process‐induced defects in fiber‐reinforced polymers (FRPs) lead to fracture nucleation due to the stress concentrations. In addition to the degradation in mechanical properties, defects can accelerate aging of FRPs and limit their service life. Efforts to understand the impact of defects have largely focused on the mechanical performance of FRPs. However, their impact on aging performance has not yet been extensively investigated. Here, we report the effect of the meso‐scale (missing yarn) and micro‐scale (micro‐crack) defects on the hygrothermal aging behavior of FRPs. Missing yarn defects were generated by pulling‐out yarns in warp and weft directions of glass fabric. Then, micro‐cracks were induced in composite laminates by acoustic emission controlled tensile loading/unloading. After exposing samples to the hygrothermal aging, we found that meso‐scale defects deteriorate mechanical/thermomechanical performance, reaching 30% decrease in the flexural strength. Notably, even though increasing micro‐crack density reduces the moisture saturation time, the aging time is reported as a more predominant design parameter, deteriorating the mechanical performance for micro‐crack‐induced FRPs. [ABSTRACT FROM AUTHOR]

For enhancing impact characteristics, woven glass fiber epoxy laminates are reinforced with short fibers. The 6‐mm‐long slender fillers, when added up to 4% in the matrix, exhibit no influence on the flexural modulus, but at 2% they maximize the laminate's flexural strength. While the dissipation energy continues to increase up to 30 J of impact, the laminates' post‐impact load bearing capacity gets significantly affected beyond 20 J. The reinforced laminates exhibit better elastic response and enhanced damage resistance with as high as 50% reduction in the visible damage area as well as up to 35% increase in the damage initiation force. The degree of damage shows excellent correlation with the visible damage area. The distinct through thickness conical region, diverging from the impact site, is attributed to the presence of microcracks oriented along the fiber directions. The cone boundary, from where the interlaminar failure initiates, is largely the manifestation of transverse matrix cracks. While the damage cone with greater divergence indicates reduced impact resistance of the laminate, the orientation of transverse matrix cracks remains unaffected by the impact energy or the filler content. At low impact energies, the failure initiated from the fiber/matrix interfaces, coalesce to form the matrix cracks, which act as a precursor to the interlaminar failure. However, at high energy levels, several failure mechanisms simultaneously develop with no clear indication of the order of damage evolution. The short fibers enhance the laminate's impact resistance either by arresting the cracks or by developing tortuous crack path with high energy dissipation. [ABSTRACT FROM AUTHOR]

Drilling process of fiber metal laminates (FML) requires a proper design of the processing parameters to prevent the occurrence of several issues and minimize defects, which can be detrimental for the integrity of the parts. These aspects become more critical in dry machining used in aeronautic field. In this scenario, the monitoring of process temperature is crucial to obtain useful information for machining optimization since many critical factors, such as matrix burnout, fiber pull‐out and delamination, depend on the heat generated during the machining. The aim of this work is to monitor the temperature measured on the tool and workpiece during dry drilling of Al/GFRP (GLARE) and Al/CFRP (CARALL) hybrid laminates. The influence of the cutting speed on the temperature trends was analyzed. Two different set‐ups were designed to measure the temperature on the tool, near the cutting edge and on the flank, and inside the laminate, in both the metallic and the composite parts. In addition, a numerical model to analyze the process temperature trend during drilling has been developed. The increasing the spindle speed from 1500 to 8000 rpm resulted in a decreasing of maximum temperatures of approximately 10°C on the tool tip and on the flank for the GLARE, and of almost 20°C in the CARALL laminates. The numerical simulation also pointed that the temperature fields is dictated by the thermal properties of carbon and glass fibers: temperature profiles within the CARALL were found smoother than those observed in GLARE. [ABSTRACT FROM AUTHOR]

The synthesis of 4,4′‐bismaleimido diphenylmethane (BMIM) and modified BMIM by its chain extension using commercially available aromatic diamines like 4,4′‐diamino diphenyl methane (DDM), 4,4′‐diaminodiphenyl sulphone (DDS), and 4,4′‐diamine diphenyl ether (DDE) was done. The synthesized materials have been characterized for structural aspects using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). The structure of BMIM was confirmed due to the presence of specific bands at ~1400 and 1705 cm−1 responsible for CC and OCNCO groups, respectively. The reduction in the heat of fusion and enthalpy of curing for chain extended bismaleimides/modified BMIM shows the influence of the swivel group in diamine during curing. The curing window has broadened for BMIM_M and BMIM_E by ~40°C and narrowed for BMIM_S by ~100°C. The mechanical properties and the chemical resistance were studied for the composites made from the BMIM and modified BMIM based composites. Fiber‐enhanced modified bismaleimide resin has improved mechanical properties. [ABSTRACT FROM AUTHOR]

An ever-growing amount of composite waste will be generated in the upcoming years. New circular strategies based on 3D printing technologies are emerging as potential solutions although 3D-printed products made of recycled composites may require post-processing. Metallization represents a viable way to foster their exploitation for new applications. This paper shows the use of physical vapor deposition sputtering for the metallization of recycled glass fiber-reinforced polymers processed by UV-assisted 3D printing. Different batches of 3D-printed samples were produced, post-processed, and coated with a chromium metallization layer to compare the results before and after the metallization process and to evaluate the quality of the finishing from a qualitative and quantitative point of view. The analysis was conducted by measuring the surface gloss and roughness, analyzing the coating morphology and thickness through the Scanning Electron Microscopy (SEM) micrographs of the cross-sections, and assessing its adhesion with cross-cut tests. The metallization was successfully performed on the different 3D-printed samples, achieving a good homogeneity of the coating surface. Despite the influence of the staircase effect, these results may foster the investigation of new fields of application, as well as the use of different polymer-based composites from end-of-life products, i.e., carbon fiber-reinforced polymers. [ABSTRACT FROM AUTHOR]

In this study, an effective microscale method based on the parametric modeling scheme of the finite volume method is improved to evaluate the effective thermal conductivity and localized thermal fields of the fiber‐reinforced composites. By comparing with the finite element method and experimental data, it is indicated that the proposed microscale method exhibits a high accuracy in solving their effective properties. On this basis, the mesh sensitivity and fiber volume fraction influence on the thermal conductivity are both investigated. The number of 36 × 36 sub‐cells is employed as the RVE model to balance the computational efficiency and simulating accuracy. In addition, affected by the thermal conductivity and microstructure of constituent materials, the heat flux distribution near the interface between phenolic resin matrix and glass fiber is relatively uniform. The study on the influencing factors of the volume fraction shows that the equivalent thermal conductivity increases slowly at the low volume fraction, while the growth rate of the equivalent thermal conductivity increases significantly at the high‐volume fraction. [ABSTRACT FROM AUTHOR]

In this article, continuous glass fiber reinforced thermoplastic prepreg is proposed using maleic anhydride grafted polypropylene (MAPP) as the matrix resin. The compression molding parameters and plying sequences are optimized. Under the process parameters of 155°C and 15 MPa, both the tensile and flexural properties achieve the maximum values, and the plying sequence of (0°/90°) possess a balanced mechanical performance. Then, MAPP/GF/Al fiber‐metal laminates are further fabricated in two stacking configurations of 2/1 and 3/2. The mechanical results showed that the tensile and bending strength were basically maintained, while the modulus are significantly enhanced by 114.9% and 135.4% in 2/1 and 3/2 fiber metal laminates (FMLs) in contrast with MAPP/GF controls. In addition, the large deflection behavior in bending test for FMLs suggest that MAPP/GF and aluminum alloy show a synergy deformation due to the good bonding between metal layer and thermoplastic resin. The optical microstructure also revealed that the interlaminar adhesion are well joined between FML constituents. The findings in this study are important from a design viewpoint of FMLs because of the lower material cost, less processing time, and good lightweight effect, which potentially be tailored to use as structural parts in automobile applications. [ABSTRACT FROM AUTHOR]

There is a growing drive in replacing conventional non-renewable fibres such as glass and carbon reinforced composites with more sustainable and renewable reinforcements such as flax, hemp, jute in biobased composites in key industry sectors such as automotive, marine, building and construction motivated by lower carbon footprint and sustainability. Despite this drive, flammability characteristics of these sustainable biobased composites are not fully understood. Through an up-to-date review, this article meticulously discusses the theme of bio-based and eco-friendly flame retardants (FRs), delving into their intricate mechanisms, flammability testing methodologies, and emerging research trends. It underscores the pivotal necessity of developing tailor-made eco-friendly FRs customised for a diverse range of materials to bolster fire safety in sustainable material applications. Furthermore, it illuminates the limitations associated with prevalent methods for assessing flammability and advocates for advancements in dynamic testing and multi-scale analyses to more accurately simulate real-world fire scenarios. This review also highlights the key characteristics of natural plant fibres and their composites critical for the development of sustainable and fire safe materials for key applications areas. Additionally, it highlights the diverse spectrum of strategies employed in the realm of flame-retardant materials research, emphasizing a pronounced shift towards eco-friendly alternatives, innovative coatings, and the ongoing exploration of synthetic biopolymers, nanocomposites, and fibres in the pursuit of heightened fire safety. Amidst the inherent challenges, this comprehensive review unequivocally underscores the pivotal role of interdisciplinary research collaboration in driving forward fire safety within the domain of sustainable materials. [ABSTRACT FROM AUTHOR]

In this paper, to enhance the toughness and heat resistance properties of polylactic acid (PLA)/polybutylene succinate (PBS) composites, the PLA/PBS matrix was modified by different glass fiber (GF), GF/SiO2, and GF/(Polyaluminium chloride) PAC fillers. Additionally, the effect of filler type, filler content, components interaction and composite structure on the mechanical and thermal properties of the PLA/PBS composites was researched. The results showed that the addition of GF, GF/SiO2 and GF/PAC make the PLA/PBS composites appear significantly higher mechanical properties compared with the pristine PLA/PBS composite. Among the different inorganic fillers, the 10%GF/1%SiO2 fillers showed excellent strengthening, toughening and heat resistant effects. Compared with the pristine PLA/PBS matrix, the tensile strength, elastic modulus, flexural strength, flexural modulus and Izod impact strength improved by 36.28%, 70.74%, 67.95%, 66.61% and 135.68%, respectively. Considering the above, when the weight loss rate was 50%, the thermal decomposition temperature of the 10%GF/1%SiO2 modified PLA/PBS composites was the highest 412.83 °C and its Vicat softening point was up to 116.8 °C. In a word, the 10%GF/1%SiO2 reinforced PLA/PBS composites exhibit excellent mechanical and thermal properties, which broadens the application of biodegradable materials in specific scenarios. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA) hydrogels are promising implants due to the similarity of their low-friction behavior to that of cartilage tissue, and also due to their non-cytotoxicity. However, their poor mechanical resistance and insufficient durability restricts their application in this area. With the development of biodegradable glass fibers (BGF), which show desirable mechanical performance and bioactivity for orthopedic engineering, we designed a novel PVA hydrogel composite reinforced with biodegradable glass fibers, intended for use in artificial cartilage repair with its excellent cytocompatibility and long-term mechanical stability. Using structure characterization and thermal properties analysis, we found hydrogen bonding occurred among PVA molecular networks as well as in the PVA–BGF interface, which explained the increase in crystallinity and glass transition temperature, and was the reason for the improved mechanical performance and better anti-fatigue behavior of the composites in comparison with PVA. The compressive strength and modulus for the PBGF-15 composite reached 3.05 and 3.97 MPa, respectively, equaling the mechanical properties of human articular cartilage. Moreover, the increase in BGF content was found to support the proliferation of chondrocytes in vitro, whilst the PVA hydrogel matrix was able to control the ion concentration by adjusting the ions released from the BGF. Therefore, this novel biodegradable-glass-fiber-reinforced hydrogel composite possesses excellent properties for cartilage repair with potential in medical application. [ABSTRACT FROM AUTHOR]

In this article, the effect of plasma treatment of polyethylene powder and glass fibers on the adhesion between polyethylene and glass fibers in composites prepared by rotational molding was studied. In contrast to other processing techniques, such as injection molding, the rotational molding process operates at atmospheric pressure, and no pressure is added to ensure mechanical interlocking. This makes reinforcing the rotomolded product very difficult. Therefore, the formation of chemical bonds is necessary for strong adhesion. Different combinations of untreated polyethylene (UT.PE), plasma-treated polyethylene (PT.PE), untreated and plasma-treated glass fibers were manually mixed and processed by rotational molding. The resulting composites were cut and tested to demonstrate the effect of the treatment on the adhesion between the composite components and on the mechanical properties of the final composites. The results showed that the treatment of both powder and fiber improved the adhesion between the matrix and fibers, thus improving the mechanical properties of the resulting composites compared to those of pure polyethylene samples and composites prepared using untreated components. The tensile strength, tensile modulus, and flexural modulus of the composites prepared using 10-min treated powder with 20 wt% of 40-min treated fibers improved by 20%, 82%, and 98%, respectively, compared to the pure polyethylene samples. [ABSTRACT FROM AUTHOR]

Jute/glass fibers epoxy composites are significantly used in construction, automotive, aerospace, and wind turbine industries. In this work, jute/glass fibers epoxy composites reinforced with two different types of filler such as the Al2O3 and SiO2 particles at different weight rations (5, 10, and 15 gm) were investigated in relation to the viscosity. The composite samples required for various tests were fabricated in conventional hand lay‐up method. Physical, thermal stability, and mechanical properties such as tensile, bending and modulus of elasticity, and viscosity tests were conducted for the fabricated composites and the effect of reinforced materials and their dispersion competency was investigated through the assessment of their microstructure with SEM, XRD, FTIR, UV, and TGA/DSC. From the results, fabricated composites exhibit linear behavior and the maximum tensile strength were found 113.438 MPa for S2 without inclusion of particles and S4 with inclusion of Al2O3 and SiO2 exhibited higher elongation 12.06%. The viscosity of the epoxy matrix showed that viscosity is increased significantly as the inclusion of the Al2O3 and SiO2 particles volume are increased. The principal weight loss takes place at 336 to 338°C, which associated weight losses were 76% for S3, 68% for S4, and 67% for S6. Jute agglomerated orientation, some void, fracture behavior, and crack have been identified, caused by lack of fiber/matrix adhesion. FTIR results show that N‐H, asymmetric stretching Si‐O‐Si, Si‐O‐C and Si‐OH bonds, C‐C stretches, C‐O bond and Al‐O‐H symmetric bonding were identified. UV analysis identified different peaks which are 254.42, 329.06, 413.5, and 473.73 nm. [ABSTRACT FROM AUTHOR]

It is necessary to investigate the flexural damage and evolution behavior of 3D printed continuous fiber‐reinforced composites. In this paper, acoustic emission technology (AE) is used to monitor the bending damage of 3D printed Kevlar fiber (KF) and glass fiber (GF)‐reinforced composites in real time, and gray relational analysis (GRA) and k‐means are utilized for clustering analysis of AE signals. Subsequently, micro‐computed tomography (micro‐CT) is employed to identify the internal damage degree. For 3D printed specimens, matrix buckling and interface failure are the main failure modes, and the number of matrix and interface damage is more than that of fiber damage, and the surface of compression side (specimen's top side) is more serious than that of the back side. KF‐reinforced composites have poor delamination resistance and more serious damage than that of GF. The average maximum stress of GF and KF‐reinforced specimens is 56.37 and 42.15 MPa, and the average bending modulus is 1576.42 and 1395.36 MPa, respectively. The combination of complementary detection methods is beneficial to the nondestructive evaluation and health monitoring of 3D printed composite materials. [ABSTRACT FROM AUTHOR]

The commercial vinyl ester (VE) resin and Furan resin (FR) were blended in various proportions. The appropriate catalyst was added. Such a blend in form of viscous syrup was applied on glass fibre and the glass-reinforced composites (GRC) were fabricated by the 'hand layup' method. The so-called GRC was formed due to interacting crosslinking between VER and FR as well as 'in situ' Diels-Alder reaction between VER and FR. All the GRC samples were tested for their physical properties and mechanical strength. ASTM methods were employed for such tests. The resultant parameters show that produced GRC samples have good mechanical properties. [ABSTRACT FROM AUTHOR]

Fused filament fabrication (FFF) is one of the most commonly used additive manufacturing technologies. However, the applied material for commercial FFF is limited. Presently, though being one of the most used polymer materials, polypropylene (PP) is rarely used in FFF because of its serious warpage and shrinkage problems. This study investigated the impact of addition of short glass fibers (GF) and ethylene propylene diene monomer (EPDM) on the printability of polypropylene random copolymer (PPR) based FFF and mechanical properties of the printed samples, as well as other properties including rheology, thermal behaviors, and morphology. The results show that the modified PPR has excellent printability, as the printed samples are of good geometrical accuracy. The addition of GF can significantly improve the strength and modulus of the composite, but it also leads to serious decrease in toughness. EPDM addition can effectively improve the toughness of the composite, showing a complementary effect with GF. This work has important meaning in expanding the FFF applicable material and in broadening the application of PP. [ABSTRACT FROM AUTHOR]

Due to their low density, natural fibers have increasingly found application in the development of systems such as wind turbine blades, airplane wing spar where flexural strength is a strong criterion for material selection. Although different researchers have studied the mechanical properties of such natural fiber composites, none has focused on the optimization of the flexural strength of pineapple leaf fiber (PALF)/glass fiber (GF) reinforced epoxy hybrid composite. This study applied the Taguchi and general regression analysis method in the optimization and modeling of the flexural strength of the PxGyEz composite. Flexural strength of 144.5 MPa at an optimum development parameter of PALF at 20% volume content, GF at 20% volume content, and fiber length of 25 mm. Analysis of variance and regression analysis was also employed to describe and model the flexural behavior of the developed composite. The PALF fiber showed to have a higher contribution to the flexural strength of the material. The equation developed to model the flexural behavior of the material showed a good correlation between the simulated value and the experimental values of the flexural strength at different combinations of manufacturing parameters. [ABSTRACT FROM AUTHOR]

Inspired by natural healing processes, a variety of synthetic self-healing materials have been developed, including fiber reinforced polymer (FRP) composites. Therefore, self-healing FRP composites have recently become a focus in the fields. This paper considers the development of autonomic self-healing on glass fiber reinforced polymer (GFRP). Vascularised GFRP was prepared from glass fiber SW280A reinforced epoxy 3218 by removing Nylon fibers after curing. A homemade ambient-curable healing resin formation (diglycidyl ether of bisphenol-A/aliphatic amine) epoxy system has been used as a self-healing agent. It was demonstrated that the post-impact compression strength recovery of the self-healing GFRP by ultrasonic C scan, micro-X-ray computer tomography (μ-CT). In this study, a autonomous, stimulus triggered, self-healing system in GFRP composites was established. Vascules were used as sensing pathway, which detected the introduction of ply delaminations and matrix microcracks following from 6.7 J/mm to 10.0 J/mm low-velocity impact events. Once connectivity between the sensing vascules and microcracks open to the ambient environment is established, the delivery of a healing agent to the damage zone is triggered. Two kinds of samples were prepared with vascules orientation which is parallel and transverse to the 0° orientation, respectively. In both samples, the damages were connected with the vascules following low-velocity impact events. The healing agents flowed into damage position and then the samples would be healed. Using this autonomous healing approach, near full recovery of post-impact compression strength (211 MPa) was achieved compared with compression after impact (202 MPa). The successful implementation of this bioinspired technology could substantially enhance the integrity and reliability of aerospace structures, whilst it would offer benefits through improving performance/weight ratio and extending lifetime. [ABSTRACT FROM AUTHOR]

Using star‐branched polyamide 6 (SPA6) with hexafunctional cyclotriphosphazene core as a matrix resin and glass fiber (GF) as a reinforcing material, star‐branched polyamide 6/glass fiber (SPA6/GF) composites with different GF content were prepared by melt‐compounding method. The star‐branched structure of SPA6 and GF content have great effects on the properties of SPA6/GF composites. Compared with linear polyamide 6 (LPA6), SPA6 with star‐branched structure has low viscosity, high melt flowability and good impregnation and adhesion to GF, which endow SPA6/GF composites outstanding processability, good surface qualities and excellent mechanical properties even when the content of GF reaches 60 wt%. The use of SPA6 resin with star‐branched structure fundamentally solves the industry problem of traditional LPA6 resin in high‐filled modification. Such high‐performance SPA6/GF composites will provide great promise for large‐scale applications. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene (PTFE) composites are commonly used engineering materials owing to their good tribological and mechanical properties. In this study, a friction pair was formed by a glass‐fiber‐reinforced PTFE composite and a chromium‐plated nickel‐based stainless steel plate (18Cr2Ni4WA). Under dry‐friction and oil‐lubrication conditions, friction and wear tests were carried out on the metal plate surface in two roughness ranges and three surface‐texture directions. The friction coefficient, wear rate, width and depth of the wear trace, wear morphology, and surface composition were analyzed. The results showed that the 90° texture direction of the steel plate with respect to the moving direction under oil lubrication and the 0° texture direction under dry friction were the texture directions with the best tribological performance. The friction and wear properties of the PTFE composite under dry friction were better than those under oil lubrication. The 0.3–0.5 μm roughness range of the steel plate was the best roughness range for the tribological properties of the matching pairs. [ABSTRACT FROM AUTHOR]

This research developed epoxy‐based glass fiber reinforced composite (GFRPs) containing multi‐scale fiber reinforcement comprising of silanized nanoclay (nano‐reinforcement) and compatibilized para‐aramid (PA) fibers (micro‐reinforcement) for enhanced impact strength and tensile‐flexural properties. VARIM technique was used for fabrication of GFRPs. Surface modification (silanization) of nanoclay was confirmed by FTIR and that of PA fibers was confirmed by SEM‐EDS and FTIR. Dispersion/morphology of nanoclay in the processed nanocomposites was determined by XRD and TEM analysis. Three different methods were used for the compatibilization of PA fibers. All methods exhibited a substantial increase in impact strength without a decrease in flexural/tensile strength. Nanocomposite containing 1.0 phr MAH treated PA fibers and 2 phr silanized nanoclay showed the highest improvement in impact strength (34% higher than the reference composite) along with minor improvements in tensile strength (6%), and flexural modulus (13%). SEM micrographs of the fractured surface of impact test samples were used to identify the mechanisms/reasons for the improved mechanical performance of the newly developed GFRPs. [ABSTRACT FROM AUTHOR]

• Automatic defect detection in glass composites using terahertz radiation. • Time-domain spectroscopy reflective scanner with an electronically controlled optical sampling scheme. • Pre-selection of C-scans with defect-related features. • Thresholding method based on Gaussian histogram fitting. • Size and depth of inclusions and delaminations determined with high accuracy. We developed a method for automatic detection of defects in glass fibre reinforced polymer (GFRP) based on a terahertz time-domain spectroscopy (TDS) system. Two GFRP specimens with round defects of different sizes (inclusions and delaminations) were measured by means of a high-speed TDS reflective scanner with an electronically controlled optical sampling scheme. The algorithm provided a series of C-scans, which were then pre-selected to identify only those with features potentially associated with defects. A thresholding method based on Gaussian fitting of the histogram was developed. The results showed that 87 % of defects were detected for the specimen with inclusions and 100 % for the specimen with delaminations. The algorithm also provided information about the depth of defects, as each C-scan was assigned to a time slice. The results demonstrate that the TDS-based system, along with the proposed histogram-based method, can automatically detect defects in GFRP. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

The use of structural polymeric composites constitutes an interesting option in the area of wind turbine blade manufacturing. Nevertheless, thick composite components may present out-of-plane waviness in their fibers, compromising the service life of the wind blades. In this context, the present study aims to study the influence of out-of-plane waviness in the fibers with different degrees of severity as well as to verify the effect of fiber glass/epoxy resin composites immersion in distilled water and saline solution in their tensile strength (σmax), modulus of elasticity (E), and deformation at break (єrup), analyzing the reinforcement/matrix interface changes. The results showed that the increase in severity promoted, in general, a statistically significant deterioration in σmax of the samples exposed to the same environmental conditioning. The conditioning led to a decrease in E and an increase in єrup, attributed to the deterioration of the interface and the plasticization of the polymeric matrix, respectively, as evidenced by fractographic analysis. The effect of severity on the єrup and σmax properties was only noticed in laminates exposed to environmental conditioning, due to water sorption favoring the deterioration of the matrix/reinforcement interface, intensifying the deleterious effect of out-of-plane waviness of fibers. [ABSTRACT FROM AUTHOR]

Due to rising environmental concerns, there has been the need to replace synthetic fibers which are non-environmentally friendly and of limited availability, with natural fibers which are eco-friendly, having considerable mechanical properties, and of a renewable source. Pineapple leaf fibers, known with high strength to weight ratio, have shown promising features. This study seeks to harness the features of these synthetic and natural fibers in a polymer composite material. In this study, a composite material PxGyEz (with x, y, and z representing the volume fraction of pineapple leaf fiber (P), the volume fraction of glass fiber (G), and fiber length respectively in Epoxy (E) matrix) was developed and its manufacturing parameters and constituents optimized for high tensile strength. The Taguchi robust experimental design technique was employed for the combination of the variable parameters of volume content of pineapple leaf (10%, 15%, and 20%), glass fiber volume content (20%, 15%, and 10%), and the fiber length (15mm, 20mm, and 25mm). The optimal combination of the variable parameters for the best tensile strength was pineapple leaf fiber at 10% volume content, glass fiber at 20% volume content, and fiber length at 15mm. The optimized composite P10G20E15 possessed a tensile strength of 95.3144MPa which was only a 5.9% deviation from the predicted optimum tensile strength. Analysis of variance showed that the glass fiber had the highest contribution of 50.64% to the tensile strength of PxGyEz, PALF 15.53%, and fiber length 28.84%. SEM images of the PALF, glass fiber, and fractured surface of the optimized material P10G20E15 revealed the surface structure which explained their different contributions to the tensile strength of the materials. A regression equation was developed to predict the behavioral trend of the tensile strength of PxGyEz. [ABSTRACT FROM AUTHOR]

Interlaminar delamination and brittle fracture of matrix have been a dilemma that fiber-reinforced composites have been faced with. Herein, the polyimide (PI) nanofiber-toughened glass fiber fiber-reinforced epoxy composites were prepared by electrospinning method and subsequent vacuum assistant resin transfer molding. The effect of spinning parameters including PI concentration, applied voltage, collector distance, jet speed and ambient humidity on the resultant fiber diameter and its distribution was systematically evaluated. The surface properties of obtained PI nanofibers were characterized by FT-IR, TG-DSC and water contact angle. The effect of PI concentration on tensile strength of PI membranes was also studied. The mode I (G Ic ) and mode II (G IIc ) interlaminar fracture toughness were measured. The results indicated that GIc and GIIc increased by 127.69% and 85.33%. The improvement of interlaminar fracture toughness may be attributed to the bridging effect of PI nanofibers. Preparation and parameter optimization of polyimide nanofiber membranes was made by electrospinning method. Then the polyimide nanofiber membranes were utilized as the toughening layer to improve the interfacial properties of fiber reinforced composites. The fracture surface was observed, and the toughened mechanism was discussed. [ABSTRACT FROM AUTHOR]