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Laminated composites with complex structures, such as L, C, or T-shaped geometries, are used at junction parts in the automotive and aerospace industries. Due to delamination failure in the curved or angled region, these structures are relatively weak in the through-thickness direction when subjected to complex loading. To overcome the issue of weak delamination resistance, this study is aimed at investigating the effect of various reinforcements on the strength properties and delamination resistance of glass/epoxy curved laminates under a four-point bending test. Experimental research was carried out on glass/epoxy curved laminates strengthened by combining three different types and geometries of reinforcement. These included chopped short fibers and glass fiber patches between each ply at the corner region of curvature, and stitching of aramid filament at the corner region of 90-degree bending. A 4 mm pitch interval was observed to enhance curved beam strength, interlaminar tensile strength and delamination resistance. The obtained findings show that glass/epoxy curved laminates reinforced with chopped kenaf short fiber, 45° glass fiber and a single stitch at the corner show greater enhancement in curved beam strength by 52.7, 34.3, and 5.6%, respectively, compared to the baseline sample. Similarly, interlaminar tensile strength improved by 69.3, 40, and 78.5% compared to the baseline sample. On the other hand, curved laminates needled with a single stitch at the corner show higher delamination resistance than other reinforcements. The experimental results correlate well with the damage morphology indicated in SEM fractographic images. [ABSTRACT FROM AUTHOR]

In this study, sol–gel-based erbium (Er3+), terbium (Tb3+) and Er3+: Tb3 co-doped 1393 bioactive glass powders and electrospun nanofibers were prepared. Structural and morphological properties of the bioactive glasses as well as the photoluminescence characteristics were investigated in detail. The median particle size and average diameter of the prepared glass powders and fibers were in the range of ~ 1.5–3.5 μm and 280–660 nm, respectively. The steady-state photoluminescence and decay kinetics of the samples were investigated under excitation (374 nm) where only Er3+ and Tb3+ ions close to Si nanoclusters can be excited. All the samples prepared in the study exhibited bright green emission upon excitation at 374 nm. Results showed that the dopant concentration and the sample morphology have significant influence on the photoluminescence and decay properties of the glasses. Sol–gel-derived bioactive glass particles exhibited stronger emission intensity, whereas electrospun nanofibers showed extended decay times. In vitro bioactivity experiments revealed that Er3+ and Tb3+ doping did not inhibit the conversion of the glass samples to hydroxyapatite treated in simulated body fluid for 30 days. It was concluded that Er3+ and Tb3+-containing 1393 bioactive glasses have a potential to be used in tissue engineering applications as well as bioimaging studies. [ABSTRACT FROM AUTHOR]

Delamination damages limit the application potential of Fiber metal laminates, hence improving the interlaminar mechanical properties has always been a research focus and challenge in this field. The toughening effect of two fillers, i.e., nano-aramid fibers (ANFs) and short-aramid fibers (ASFs), which are used at the interface of glass fiber-aluminum laminates, have been investigated. Chemical pretreatments of aluminum alloy surface were conducted to ensure the better adherence between the fiber composites and metal sheets. Results revealed that Mode-I and Mode-II fracture toughness of the laminates could be simultaneously improved when using the two fillers at the interface of glass fiber-aluminum laminates. Attributed to the better dispersion of ANFs in epoxy matrix, the toughening performance of ANFs is better than that of ASFs in this case. The mechanism of interlaminar toughening was revealed with electron microscopic observation of fracture morphology. Meanwhile, the finite element analysis based on bilinear cohesive zone model was adopted to predict the increased interlaminar tensile and shear strength. [ABSTRACT FROM AUTHOR]

Increasing environmental concern has put forward the use of flax fibers instead of glass fibers in composite materials. However, durability performances of these bio-fibers remain one of their main issues. This study focuses on the hydrothermal aging of flax fibers. Flax tows were immersed in distilled water at a temperature of 80 °C for different durations. The effect of the hydrothermal aging on mechanical properties of flax tows was evaluated. Results showed a strong decrease in the maximal strength and the stiffness by 31% and 49%, respectively, until one week of aging. Multi-scale analyses were realized to explain these evolutions. Morphological characterization highlighted a washing of fiber surfaces during the hydrothermal aging, extracting amorphous components as pectins, lignins and amorphous hemicelluloses from cortical tissues. We showed that this morphological evolution impacted the fiber crystallinity. Based on a mechanical analysis, we showed that amorphous components extraction may be at the origin of the material softening. Moreover, the amorphous phase in particular the natural binder pectin would play a major role in the fiber stiffness but does not modify the flaws at the origin of failure. [ABSTRACT FROM AUTHOR]

Polybenzoxazine (PBO) aerogels were prepared from 4,4′-diamino-diphenylmethane (MDA) benzoxazine monomer by HCl-catalyzed ring-opening polymerization at room temperature after CO2 supercritical drying. This study systematically analyzes the microstructures, thermal insulation properties, compressive properties, and thermal stabilities of the PBO aerogels. The aerogel structure was a cross-linked three-dimensional network with a pore size of 10–140 nm. The conductivity of the aerogels was 0.035–0.057 W/m K under ambient conditions, reducing to 0.009 W/m K at 3 Pa. The compressive strength reached 14.42 MPa under 10% strains, much greater than in SiO2 aerogels of similar density (0.40 g/cm3) reinforced by high-silica glass fiber, which is only 1.30 MPa. Hydrogen bonding interaction was found to be critical for constructing the three-dimensional network structure of the aerogels. This work provides a valuable reference for exploring new structures and expanding the thermal insulation applications of PBO aerogels. [ABSTRACT FROM AUTHOR]

The influence of the fiber/matrix interface of pultruded glass fiber-reinforced polymer (GFRP) composites exposed to hygrothermal environments, including deionized water immersion and saltwater immersion at 20 ± 5 °C, 30 ± 1 °C, and 60 ± 1 °C for 180 days, was investigated. The effect of moisture absorption on tensile properties was discussed. After 180 days of immersion in deionized water, tensile strength and modulus of specimens decreased 25.7% and 26%, whereas the equivalent respective losses were 2.1% and 18.2% for specimens immersed in saltwater. The short-beam-shear test and the single-fiber fragmentation test were selected to reflect the degradation of macro- and micro-interfacial properties, respectively. After 180-day immersion in deionized water and saltwater at 60 ± 1 °C, the inter-laminar shear strength of specimens decreased 28.8% and 18.5%, respectively, and the corresponding interfacial shear strength decreased 53.2% and 23.5%, indicating that the diffusion rate of micro-interface was higher than that of macro-interface in the fiber direction. Immersion in all media leads to pronounced degradation in tensile strength, modulus, and inter-laminar shear strength. Furthermore, based on the change of interfacial strength and Weibull distribution, a prediction model was proposed to describe the degradation trends and temperature effects on ultimate bearing capacity of pultruded GFRP composites in hygrothermal environments. [ABSTRACT FROM AUTHOR]

The recent developments in the aeronautical structure industry have seen a sharp rise in the use of polymer composite materials. The performances of all aerodynamic surfaces are heavily dependent on the shape and the surface form. The modification of these surfaces due to condensation and melting of ice can cause catastrophic decreases in the aerodynamic performance. In this study polymer composite materials as heater were made and studied. The feasibility of using advanced polymer composites for de-icing application was validated and studied through experiments. It consists of thin carbon nanotubes (CNTs) Bucky paper placed between two glass fibers veils and then infiltrated with an epoxy polymer resin and cured. The composite can be heated up very quickly using an electrical power source. The idea of using this new material as a heater and de-icing material was explored experimentally. For that purpose, the temperature distribution was monitored at different positions of the panel using thermal imaging. Experimental results show that the surface temperature of the panel increases gradually as the heating time increases. This temperature increased in a short time period of heating time, implying that the composite panels with CNTs Bucky paper display an excellent heating performance. [ABSTRACT FROM AUTHOR]

Polymeric foams are extensively used as the core materials in sandwich structures and the core material is typically bonded between relatively thin fibre-composite skins. Such sandwich structures are widely used in the aerospace, marine and wind-energy industries. In the present work, various sandwich structures have been manufactured using glass-fibre-reinforced polymer (GFRP) skins with three layers of poly(vinyl chloride) foam to form the core, with the densities of the foam layers ranging from 60 to 100 kg/m3. This study has investigated the effects on the quasi-static flexural and high-velocity impact properties of the sandwich structures of: (a) the density of the polymeric-foam core used and (b) grading the density of the foam core through its thickness. The digital image correlation technique has been employed to quantitatively measure the values of the deformation, strain and onset of damage. Under quasi-static three-point and four-point bend flexural loading, the use of a low-density layer in a graded-density configuration reduced the likelihood of failure of the sandwich structure by a sudden force drop, when compared with the core configuration using a uniform (i.e. homogenous) density layer. The high-velocity impact tests were performed on the sandwich structures using a gas-gun facility with a compliant, high-density polyethylene projectile. From these impact experiments, the graded-density foam core with the relatively low-density layer located immediately behind the front (i.e. impacted) GFRP skin was found to absorb more impact energy and possess an increased penetration resistance than a homogeneous core structure. [ABSTRACT FROM AUTHOR]

A glass fiber/polyimide (PI)/SiO2 composite aerogel (FPS aerogel) was prepared by dispersing glass fibers in PI/SiO2 hybrid sol derived from 4,4′-oxydianiline (ODA), pyromellitic dianhydride (PMDA) and tetraethoxysilane (TEOS) with supercritical CO2 fluid drying technology. The SiO2 primary particles were combined with PI chains which improved the strength of the composite aerogel, and the glass fibers inhibited the shrinkage deformation during the drying process by acting as the supporting skeletons. Effects of PI contents on the density, shrinkage, thermal conductivity and mechanical properties of the FPS aerogels were investigated. The as-prepared FPS aerogels had low densities (0.116-0.145 g/cm3), high specific surface area (844-963 m2/g), low thermal conductivity (0.0268-0.0280 W m−1 K−1 at room temperature) and relatively high compression strength (0.12-0.29 MPa) with integrated nanostructures, fewer powders and stronger fiber/aerogel matrix interfaces. The density, the shrinkage, the thermal conductivity and the compression strength of the FPS aerogels increased with the increasing PI content. This research provided a new method employing PIs and glass fibers as strengthening phases to improve the mechanical properties of SiO2-based aerogels. [ABSTRACT FROM AUTHOR]

Kinetics of the dissolution of E-glass fibres in alkaline solutions was investigated. To allow an accurate determination of conversion, glass fibres were immersed individually in the corrosive medium and the diameter change was measured with the use of a scanning electron microscope. Few studies have been reported in the literature on the kinetics of E-glass fibre dissolution or the dissolution of individual fibres. Our experimental results fit well in the zero-order and shrinking cylinder models, suggesting either the diffusion of hydroxide ions through the solution or the glass fibre etching itself was rate-limiting step. The rate constant for the reaction of glass fibre with alkaline solution at 95 °C was found to be between 1.3 × 10 and 4.3 × 10 g/(m s). The reaction order ( n) was determined as 0.31-0.49 with respect to the alkaline solution, and the activation energy was 58-79 kJ/mol. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polymer composites (GFRP) were prepared and reinforced with two types of multiwalled carbon nanotubes, i.e., amino-functionalized (ACNT) and pristine nanotubes (PCNT). Incorporation of ACNT leads to a significant decrease in equilibrium water content and diffusion coefficient vis-à-vis GFRP composites when immersed in seawater (SW) and distilled water (DW). The experimental results illustrate that the material degradation of the composites is significantly more on immersion in SW as compared to DW. Interestingly, a decrease in mechanical properties was observed initially; however, at a later stage the trend reversed and a recovery in the mechanical properties was seen. This recovery in mechanical properties is ascribed to the possible secondary crosslinking network between excess sodium ions in seawater with the hydroxyl groups of cured epoxy and also to the unreacted silanols on the glass fiber surface. On the contrary, PCNT composites revealed a continuous decreasing trend in mechanical behavior versus aging duration. The present study suggests that it may be advantageous and safer to re-condition (for 15-20 days) FRP nanocomposite parts before being installed in naval vessels. [ABSTRACT FROM AUTHOR]

The failure properties of flax fibres were investigated using a tow behaviour-based approach that was developed on ceramic and glass fibres. The Weibull and normal strength distributions of filament failure strains and the true statistical parameters were extracted from the tensile curve of a tow test specimen made of several 100 of filaments. Tensile tests were carried out on flax tows possessing more than 1000 continuous elementary fibres. The force-strain curves were found to follow the theory of bundles of independent and parallel continuous filaments. Weibull and normal distributions of filaments failure strains were reproducible and in excellent agreement. The results of the present work are compared to strengths of elementary and technical fibres reported in the literature. The dependence of statistical parameters on factors including sample size and selection, and method of experimental data analysis was investigated. For this purpose, subsets of failure strains were analysed, and the normal distribution-based approach was applied to sets of failure strain data of elementary fibres reported in the literature. Finally, the flax fibre was compared to E glass fibre using statistical distributions of failure strengths. [ABSTRACT FROM AUTHOR]

Five fluoro-phosphate (FP) glasses of different compositions, 49.5PO-10AlF-10BaF-10SrF-10PbO-10M (M = LiO, NaO, KO, ZnO, and BiO), doped with 0.5 mol% praseodymium were prepared by melt quenching technique. For these glass matrices, structural, thermal, dielectric, electrical, and optical properties have been studied. The structures are characterized by XRD, Fourier transform infrared, Raman spectroscopy, and solid-state P and Al magic angle spinning nuclear magnetic resonance techniques. The chemical and electronic states of these glass materials are characterized by X-ray photoelectron spectroscopy. The thermal stability for the host glass matrix is estimated from differential scanning calorimetry technique. From the impedance spectroscopy, various parameters, viz. electrical conductivity, dielectric constant ( ε′), and dielectric losses (tan δ), at various frequencies and temperatures have been measured. X-ray absorption near-edge spectroscopy was used to study the electronic structure of praseodymium in the host glass matrices. By analyzing the absorption spectra with Judd-Ofelt theory, three intensity parameters (Ω, λ = 2, 4, 6) are obtained. In turn, these parameters are used to calculate radiative properties such as emission probabilities ( A), radiative lifetimes ( τ), and integrated absorption cross sections (Σ) of different Pr transitions. Luminescence parameters such as stimulated emission cross sections ( σ) and branching ratios ( β) have been studied through photoluminescence spectra. Further, decay time constants are estimated from the decay profiles of Pr-doped different FP glasses. [ABSTRACT FROM AUTHOR]

We investigated the effect of graphene nanoplatelets (GnPs) with two different lateral dimensions on the morphology, flexural, and thermo-mechanical properties of multiscale GnPs/glass fiber/epoxy composites. First, 3 and 5 wt% of GnP-C750 (<1 µm in diameter) and GnP-5 (5 µm in diameter) were individually integrated into epoxy suspension through a combination of calendaring and sonication processes. The GnPs/glass fiber/epoxy composites were then fabricated by incorporating glass fibers into the GnPs/epoxy mixture. Results showed that the flexural modulus of the GnPs/glass fiber/epoxy composites was improved by 11.5 and 26.3 % with the addition of 5 wt% GnP-C750 and GnP-5, respectively. At the same filler content, the storage modulus of the glass/epoxy composites incorporated with GnP-C750 and GnP-5 at 30 °C was enhanced by 10.2 and 28.2 %, respectively. The flexural strength of the 3 wt% GnP-5-reinforced glass fiber/epoxy composite is 16.2 % higher than that of the glass fiber/epoxy composite. The dispersion results of GnPs in the composites and the interfacial interactions between fibers and modified matrix were evaluated by scanning electron microscopy. [ABSTRACT FROM AUTHOR]

Continuous glass fiber polymer-matrix composites are electrically insulating and used for printed wiring boards, but their thermal conductivity needs to be increased without sacrificing the electrical insulation ability. The through-thickness thermal conductivity of these epoxy-matrix composite laminates with in-plane fibers is found to be effectively modeled using the Rule of Mixtures with fibers and matrix mainly in parallel in the through-thickness direction, in contrast to the series model that is effective for previously studied carbon fiber composites. For the glass fiber composites, the through-thickness conductivity is similar to the in-plane conductivity. The conductivity for woven fiber composites is increased by up to 80 % by curing pressure increase (from 0.69 to 4.0 MPa), up to 50 % by solvent (toluene or ethanol) treatment of the prepreg for partial surface resin removal, and up to 90 % by boron nitride nanotube (BNNT) incorporation along with solvent treatment. The highest through-thickness thermal conductivity reached is 1.2 W/(m K), which is higher than those of all prior reports on glass fiber composites. The interlaminar interfaces are negligible in through-thickness thermal resistance compared to the laminae, as for previously studied carbon fiber composites. The fiber contribution dominates the lamina resistance. The fiber-fiber interface contribution to the lamina resistance decreases significantly with curing pressure increase or composite modification involving BNNT incorporation or solvent treatment of the prepreg. [ABSTRACT FROM AUTHOR]

The failure strains of E-glass fibers aged in air for up to 6 months at 50 °C/80 % relative humidity were measured in ambient air and in liquid nitrogen using the two-point bending method, and were related to changes in surface morphology as characterized by optical microscopy and scanning electron microscopy. The failure strain of E-glass fibers decreased by 1.5 % per day during the first week of aging, but then more slowly (0.01 % per day) over the next 6 months, with similar trends noted for fibers tested in room temperature air and in liquid nitrogen. Small droplets form on the surfaces of fibers aged within the first week and reactions between the droplets and glass create surface defects that degrade failure strains. Over longer times, calcium carbonate crystals form on the fiber surfaces. [ABSTRACT FROM AUTHOR]

In this study, glass fiber (GF) was grafted by an amino-terminated hyperbranched polymer (ATHBP). The structure of GF-ATHBP was characterized by attenuated total internal reflectance infrared spectroscopy, H nuclear magnetic resonance spectroscopy, thermal gravimetric analysis, and field emission scanning electron microscopy (FESEM). The modified GFs were used to produce high-performance epoxy composites. The effects of GF-ATHBPs on the mechanical properties of composites were investigated, discussing the results from tensile, flexural, and impact tests. The results showed that the grafting ratio of ATHBP on GF was 7.6 %, and the thickness of ATHBP layer was about 1.9 μm. And the incorporation of GF-ATHBPs could favorably improve the mechanical properties of epoxy resins. FESEM morphologies showed that the excellent compatibility and interaction may be associated with the great enhancement of mechanical properties of epoxy/GF-ATHBP composites. [ABSTRACT FROM AUTHOR]

Aerosol filtration using electrospun cellulose acetate filters with different mean fiber diameters is reported, and the results are compared with those for two conventional filter media, a glass fiber filter and a cellulose acetate microfiber filter. The performance of these filters was studied using two aerosols, one solid (NaCl) and one liquid (diethyl hexyl sebacate), under conditions of relatively high face velocity (45 cm/s). The experimental observations are compared to theoretical predictions based on single fiber filtration efficiency. Our results indicate that the mechanisms for single fiber filtration efficiency provide reasonable predictions of the most penetrating particle size (MPPS), in the range of 40-270 nm, percentage penetration from 0.03 to 70 %, and fiber diameter in the range from 0.1 to 24 µm. Using an analysis based on blocking filtration laws, we conclude that filtration by cake formation dominated in the case of NaCl aerosols on electrospun filter media, whereas filters with larger fiber diameter showed a transition in mechanisms, from an initial regime characterized by pore blocking to a later regime characterized by cake formation. The liquid aerosol did not exhibit cake formation, even for the smallest fiber diameters, and also had much smaller influence on pressure drop than did the solid aerosol. The electrospun filters demonstrated slightly better quality factors compared to the commercial glass fiber filter, at a much lower thickness. In general, this study demonstrates control of the properties of electrospun cellulose acetate fibers for air filtration application. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced plastic composites (GFRPs) are often suffered to impact loadings; it is essential to improve its damage-resistant properties and understand the energy absorption mechanisms. In this work, the low-velocity impact behaviors of GFRPs were investigated in consideration of epoxy resins modified with 0, 0.4, and 0.75 % multi-walled carbon nanotubes (MWCNTs) by weight content and pre-stretched fabric at 0, 1.27, and 2.47 kg weight. In comparison with pure GFRPs sample, MWCNT-modified specimens are effective in improving the impact resistance under impact energies at 9, 16, and 22 J in terms of reduced damage factor and enhanced perforation threshold. Microscopic fractographic analysis indicated that the incorporation of MWCNTs in epoxy matrix offered additional mechanisms through breakage, bridging, and pull-out of carbon nanotubes to favor load transfer effect, prevent crack propagation, and thus dissipate more energy. The dynamic thermo-mechanical analysis proved that MWCNTs improved the storage modulus and glass transition temperature of the composites. In addition, the pre-stretched GFRP composites showed more impact resistant than the non-stretched ones through instant load transfer effect. [ABSTRACT FROM AUTHOR]

Degradation properties were studied for polylactic acid (PLA) and phosphate glass fibre (40PO-24MgO-16CaO-16NaO-4FeO, denoted as P40) reinforced unidirectional (UD) and randomly mat (RM) PLA composites using phosphate buffer saline (PBS) media over a range of temperatures from 21 to 85 °C. Glass transition and melting temperatures for PLA decreased from 61.3 and 167.4 to 52.7 and 151.6 °C, respectively, and crystallinity increased from 9.2 to 58.3 % during 3 days of degradation period in PBS media at 85 °C. Appearance of sharp crystalline peaks after degradation at higher temperatures which was confirmed via X-ray diffraction analysis was also indicative of increase in crystallinity. However, flexural strength decreased by approximately 20 % (for PLA) and by around 50 % (P40 RM and P40 UD composites) of the initial strength after degradation in PBS at 37 °C. No significant changes in mechanical properties were observed before and after degradation of composites at 21 °C for 56 days. Monomodal molecular weight distribution for the PLA before and after degradation in PBS at 37 °C was replaced by bimodal after degradation at higher temperatures. Arrhenius equation applied for the change in molecular weight of the polymer and composite samples and the obtained degradation activation energies were 85.4, 78.7 and 74.1 kJ mol for PLA within PLA alone, P40 RM and P40 UD composites, respectively. Time prediction was applied to correlate short-term degradation (at elevated temperatures) to the long-term effects (at 37 °C) using both 'tipping point' and molecular weight as co-ordinates. [ABSTRACT FROM AUTHOR]

Confocal laser scanning microscopy with fluorescent markers and index matching has been used to collect three-dimensional (3D) digitized images of electrospun fiber mats and of a borosilicate glass fiber material. By embedding the fluorescent dye in either the material component (fibers) or pore space component (the index-matching fluid), acquisitions of both positive and negative images of the porous fibrous materials are demonstrated. Image analysis techniques are then applied to the 3D reconstructions of the fibrous materials to extract important morphological characteristics such as porosity, specific surface area, distributions of fiber diameter and of pore diameter, and fiber orientation distribution; the results are compared with other experimental measurements where available. The topology of the pore space is quantified for an electrospun mat for the first time using the Euler-Poincaré characteristic. Finally, a method is presented for subdividing the pore space into a network of cavities and the gates that interconnect them, by which the network structure of the pore space in these electrospun mats is determined. [ABSTRACT FROM AUTHOR]

This report describes the direct melt processing of inorganic tin fluorophosphate (TFP) glass fibers with average diameters ranging from 2 to 4 µm via centrifugal Forcespinning. This was accomplished by using a TFP glass with low glass transition temperature ( T) and the melt processing capability of Forcespinning. The thermal behavior of TFP glass fibers was investigated by differential scanning calorimetry and thermogravimetric analysis, while the compositional evolution of the fibers was studied using energy-dispersive spectrometry and Fourier-transform infrared spectroscopy. These fibers exhibited excellent thermal stability after thermal post-treatment at 300 °C. The T of the thermally treated fibers increased by 100 °C compared to the bulk material. The fibers were found to undergo dehydration and loss of fluorine during thermal treatment, resulting in a rigid and crosslinked glass network with enhanced thermal stability and increased T. The enhanced thermal stability demonstrated the potential of TFP fibers for high temperature catalysis and chemical filtration applications. [ABSTRACT FROM AUTHOR]

Long and short glass fibers (GF) were incorporated into the polyamide 6,6 (PA66)/polypropylene (PP) mixtures in order to enhance the thermomechanical properties. The effect of fiber length and processing procedures on tensile strength, flexural modulus, impact strength, and heat deflection temperature has been investigated. Miscibility behavior of the PA66/PP mixtures has been examined by performing differential scanning calorimetry analysis and theoretical calculation. The mixtures exhibiting broad coexistent regions such as crystal + crystal (Cr + Cr), crystal + liquid (Cr + L), and liquid + crystal (L + Cr) revealed a significant improvement in thermal and mechanical properties by the addition of GF. Especially, long fiber-reinforced thermoplastics showed better performances compared to short fiber-reinforced thermoplastics at the same filler loading. From the morphological observation of the fractured surface, it was realized that the incorporation of long GF after the melt blending of PA66 and PP was very effective to attain high thermomechanical properties due to the better homogeneity and compatibility. [ABSTRACT FROM AUTHOR]

The results of a study on the properties of glass fibres after thermal conditioning at typical engineering thermoplastic processing temperatures are presented. The mechanical performance of rovings and single fibres of well-defined silane- and water-sized E-glass fibre samples was investigated at room temperature after thermal conditioning at temperatures up to 400 °C. Thermal conditioning for 15 min led to strength degradation of >50 % at higher temperatures. The tensile strength of silane-coated fibres was relatively stable up to 300 °C but exhibited a precipitous drop at higher conditioning temperatures. The water-sized fibres exhibited an approximately linear decrease in strength with increasing conditioning temperature. The strength distribution of the water-sized fibres could be well represented by a unimodal three-parameter Weibull distribution. The strength distributions of the sized fibres were more complicated and required the use of a bimodal Weibull distribution. The results are discussed in terms of the changes in surface coating and bulk glass structure during heat conditioning. [ABSTRACT FROM AUTHOR]

A thermomechanical analysis (TMA) procedure has been developed with the capability of probing the thermal behaviour of glass fibre. A single glass fibre was successfully mounted into TMA fibre configuration and several thermomechanical programmes were carried out over a wide temperature range from 20 to 900 °C. It was found that measured coefficient of linear thermal expansion of boron-free E-glass fibre remained constant below 300 °C and the values had an excellent agreement with that found in the literature. At higher temperatures an abrupt length change in glass transition region allowed for the determination of glass transition temperature. The results from isothermal measurement showed significant fibre length shrinkage, which was a function of both temperature and time. It follows that there exist two mechanisms, thermal expansion and structural relaxation, which together account for overall thermomechanical responses of glass fibre. The former is related to the decrease of Young's modulus at elevated temperatures and the latter is considered responsible for the observed increase of room-temperature Young's modulus after thermally conditioning glass fibre at various temperatures. [ABSTRACT FROM AUTHOR]

In order to further investigate shear-induced interfacial crystallization of polymer-based composites, an improved fiber-pulling device was designed and built. Its peculiar characteristic is that a force transducer is assembled to in situ monitor the variation of interfacial shear stress between the polymer matrix and pulling fiber. Thus, the relationship between interfacial shear stress and the subsequent crystalline morphology can be quantitatively established. In the preliminary study via this device, isotactic polypropylene (iPP)/glass fiber composite was adopted as a model system. The results indicate that interfacial crystallization kinetics is promoted by the presence of interfacial shear stress. Furthermore, there are two thresholds of interfacial shear stress for interfacial crystalline morphology. To be specific, one (0.017 MPa) is for the induction of iPP nucleation, above which α-form iPP crystals are obviously encouraged during the subsequent isothermal crystallization; the other is for the generation of β-form iPP crystals (0.042 MPa), above which β-form crystals are favored to be triggered in the transcrystalline region. [ABSTRACT FROM AUTHOR]

Acid corrosion and stress corrosion characteristics of E-glass fibers with and without boron (BO or B) were carefully studied, using 1 N HSO acid at 96 °C and room temperature, respectively. The effect of boron on glass resistance to the acid attack is elucidated in conjunction with structural roles of B, Al, and Ca in the glass. Scanning electron microscopy with energy dispersive spectrometer (SEM/EDS) characterization was performed on the selective fiber samples before and after the acid leaching. For high boron-containing fibers, the results showed the formation of alteration layer enriched in Si as a result of depletion of both Ca and Al. Chemical analysis of the high boron fibers before and after 24 h acid leaching and the solution after 24 h test further confirmed that B, Ca, and Al in the glass fibers preferentially dissolved in the acid solution. Glass fiber dissolution mechanisms were discussed with a proposal that acid corrosion attack in boron-containing E-glass is controlled by hydrolysis of aluminoborate complex species (less than 10 nm) separated from the silicate glass network, whereas the acid corrosion attack in boron-free E-glass is controlled by hydrolysis of the silicate network, where 4-coordinated aluminum in the network is locally charge compensated by Ca. [ABSTRACT FROM AUTHOR]

Mechanical performance of commercially manufactured unsized and γ-aminopropylsilane sized boron-free E-glass fibres has been characterised using single-fibre tensile test. Both apparent fibre modulus and fibre strength were found to strongly depend on fibre gauge length. The average strength of sized fibres was found 40-80 % higher than unsized fibres at different gauge lengths. Weibull analysis suggested that the failure mode of unsized fibres could be described by unimodal Weibull distribution, whereas the strength distribution of sized fibres appeared to be controlled by two exclusive types of flaw population, types A and B. Comparison of the Weibull plots between unsized and sized fibres revealed that the strength of unsized fibres was likely to be dominated by type A flaws existing on the bare glass surface and type B flaws may be related to the defects on the glass surface coated with silane. This was partially supported by the observation of fractured cross-sectional area using SEM. It was, therefore, proposed that the strength difference between unsized and sized glass fibres may be more reasonably interpreted from the surface protection standpoint as opposed to the flaw healing effect. The results obtained from this study showed that silane coupling agent plays a critical role in the strength retention of commercially manufactured E-glass fibres and the silane effect on the fibre strength is also affected by the change in gauge length of the sample. [ABSTRACT FROM AUTHOR]

This paper investigates the use of novel phosphate-glass fibre-reinforced rods as resorbable intramedullary nails. Random and unidirectional fibres were moulded into composite rods by forging at ~100 °C. Rods produced using non-woven random mats (RM) showed little improvement in mechanical strength over the unreinforced polylactic acid (PLA) rods. This was suggested to be due to the breakdown of the fibres during the manufacturing process; the length of the fibres decreased from 10-mm (initial) to ~1.2 mm. Modulus and stiffness values for P50 RM rods were higher than those for the PLA rods which could be due to the orientation of the fibres during the rod manufacture process. Rods produced using long fibres parallel to the length of the rod displayed superior mechanical properties, not only against the PLA rods but also cortical bone. Maximum flexural, shear and compressive strengths were 242, 87 and 400 MPa, respectively. A flexural modulus of 25 GPa was achieved, with shear and compressive stiffness values of 6 and 21.5 kN mm, respectively. These unidirectionally reinforced phosphate glass fibre PLA composites have huge potential to be used as IM fixation devices. [ABSTRACT FROM AUTHOR]

It is well known that the strength of glass fibers increases with increasing strain rate. Consequently, impact strength of glass fiber is competitive with that of carbon fiber. This strengthening phenomenon is well recognized for bulk glass. Strain-rate dependence of the strength for bulk glass was described by considering slow crack growth in glass. The analytical model that considered the slow crack growth of glass is proposed to predict the strength of glass fibers. The proposed model considered the stress corrosion limit and a constant crack velocity region. Calculations showed almost same results with the previous model, however, some differences were confirmed. To discuss the validity of the analysis, tensile tests of E-glass fiber bundles were conducted at various strain rates. It was observed that the fracture behaviors differ with the strain rates. Experimental results showed that the strength of E-glass fibers increased with increasing strain rate. Furthermore, we confirmed that the analytical results were in good agreement with the experimental results. The strain-rate dependence of the strength of glass fibers was successfully predicted by considering the slow crack growth in glass. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the reinforcing effect of woven and unidirectional glass fibers and the effect of post-curing on the flexural strength and flexural modulus of glass fiber-reinforced composites. A series of composites containing 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)-phenyl]propane and triethyleneglycol dimethacrylate matrices and different reinforcements of unidirectional or woven glass fibers were prepared. The samples, 25 × 2 × 2 mm, were cured with a halogen curing lamp, followed by additional curing by thermal treatment at 135 ± 5 °C temperature and 60 psi pressure. Samples were tested before and after post-curing in order to determine the flexural strength and flexural modulus. The degree of reinforcement with glass fibers was varied between 14 and 57 wt% or 7.64 and 38.44 vol% by changing the number of unidirectional bundles or woven glass fiber bands in the composites, respectively. The obtained flexural strength values were in the range of 95.20-552.31 Mpa; the flexural modulus ranged between 2.17 and 14.7 GPa. The highest flexural strength and flexural modulus values were recorded for samples with unidirectional glass fibers. The mechanical qualities of the glass fibers-reinforced composites increased after post-curing treatment. Increasing of the glass fiber amount in the experimental composites improves both flexural strength and modulus. SEM micrographs of fractured composites indicate a strong interfacial interaction between the glass fibers and the polymer matrix. [ABSTRACT FROM AUTHOR]

In this study, isothermal crystallization kinetics of polyamide 6 (PA6) composites reinforced with surface-treated glass fiber (GF) and natural, clay-type mineral (MN) were investigated by differential scanning calorimetry method in the presence and absence of a nucleating agent (NA). Microstructural features of the composites and interfacial interactions between filler and polyamide phases were also quantified by rheological measurements. The kinetic parameters for the isothermal melt-crystallization process of the samples were determined with the Avrami and Lauritzen-Hoffman models. The crystallization activation energies were determined by the Arrhenius method. It was found that the both fillers yielded a significant increase in the storage modulus of PA6. Kinetic calculations showed that the MN has a more pronounced acceleration effect on the crystallization rate of PA6 than the GF. Introduction of a small amount of NA significantly favored the isothermal crystallization rate of GF-reinforced PA6 but did not accelerate that of MN-reinforced one. Based on the results, it has been highlighted that PA6 composites reinforced with surface-treated GFs and including a small amount of clay-like mineral as a cheap and easy-accessible minor filler could yield the best performance for the injection-molded PA6 parts because the GF enhances the mechanical properties and the clay-like mineral accelerates the crystallization rate. [ABSTRACT FROM AUTHOR]

Natural fiber-reinforced polymers or biocomposites are becoming increasingly popular as an environment friendly alternative to traditional glass fiber-reinforced thermoplastics. The mechanical properties of reinforced biocomposites, such as flax/polylactic acid (PLA), are largely governed by the level of interfacial interactions between the two constituents apart from their intrinsic properties. The hierarchical organization of various polysaccharides present in natural fibers results in complex mechanisms at the interface which are still poorly understood and difficult to analyze through a traditional approach that rely on indirect assessments. The possibility of measuring direct adhesion force between individual particles using the colloidal force microscopy has been exploited here by developing an experimental set-up in which a micrometer colloidal PLA bead is brought into close contact with molecularly smooth polysaccharide surfaces that mimic the main constituents of flax fibers, cellulose, hemicellulose, and pectins. Adhesion force measurements performed under ambient and low relative humidity conditions indicate that cellulose/PLA is the weakest interface in the biocomposite. Moreover, the results emphasize the important role of water molecules for the more hydrophilic polymers in flax fibers that takes place in the fundamental forces involved in the adhesion phenomena at the biocomposite interface. [ABSTRACT FROM AUTHOR]

This study aims at systematically extracting fiber/matrix interfacial strength in short-glass fiber-reinforced polymer composites using an experimental micromechanics approach which employs mechanical properties and residual fiber length distributions to derive the apparent interfacial shear strength. We started from neat high-impact polystyrene matrix short-glass fiber-reinforced composites (HIPS/GF) with varying fiber loading and proceeded toward HIPS/GF hybrid composites containing micro- and nano-fillers where complex fiber/matrix interfacial interactions exist. It was found that apparent interfacial shear strength does not vary with fiber content, while the presence of fillers with different length-scales alters fiber/matrix interactions depending on their influence on physical properties of the polymer matrix, particularly in the vicinity of reinforcing fiber surfaces. [ABSTRACT FROM AUTHOR]

Wavelength converters have been proposed as one of the ways to achieve higher efficiency in third generation solar cells. The idea is to shift the wavelength of the light absorbed by the solar cell to the spectral region where the device is most efficient. Higher energy photons are often absorbed unproductively near the front contact of the solar cells. By the application of photoluminescent materials these photons are transformed into longer wavelength ones, which contribute more effectively to the generated photocurrent. In this study the improvement that a wavelength converter containing Tb ions can produce on the efficiency of a thin film silicon single junction solar cell under AM 1.5 solar radiation is assessed by model calculations. The absorption and emission of a specified number of Tb ions in a fluoride glass layer or plate is calculated on the basis of literature data. It is presumed that such a plate is placed in front of the solar cell and modifies the solar spectrum falling on the cell. This modified solar spectrum is used to calculate the efficiency of two model solar cells, an amorphous silicon and a microcrystalline silicon one, using the program Afors-Het 2.2. The amount of Tb ions per unit area in the wavelength converter layer is varied. In the best case the efficiency of the a-Si:H solar cell improves by 1% and that of the microcrystalline silicon cell by 2.3%, in comparison to that calculated with the unmodified AM 1.5 spectrum. [ABSTRACT FROM AUTHOR]

Use of carbon nanotubes as additives to composite parts for the purpose of increased damping has been the subject of much recent attention, owing to their large surface area per weight ratio which provides for frictional losses at the carbon nanotube-resin matrix interface. This article presents an experimental study to quantify the structural damping in composites due to the addition of carbon nanotubes to thermosetting resin systems with and without fiberglass reinforcement. Carbon nanotubes of varying quantity and morphology are ultrasonically dispersed in epoxy resin and are compression molded to form test samples that are used in forced vibration, free vibration with initial tip deflection, and tension tests to determine their damping ratio, specific damping capacity, and Young's modulus. Results show increased stiffness and specific damping capacity with the addition of carbon nanotubes and particularly increased frictional loss with increasing surface area to weight ratio. The addition of fiberglass reinforcement to composite samples is shown to reduce the effective damping ratio over plain epoxy samples and carbon nanotube-filled epoxy samples. [ABSTRACT FROM AUTHOR]

Satisfactory impregnation of glass fiber mats may be obtained with isotactic polypropylene/montmorillonite (MMT) nanocomposites under conditions comparable with industrial conditions. However, it is demonstrated here that the high melt viscosity of the nanocomposite matrix at low shear rates may significantly influence the release of the compressive load in the glass mat and hence the glass fiber distribution in consolidated specimens. Thus, depending on the initial lay-up and overall glass fiber content, the bending modulus may either increase or decrease with increasing MMT content, whereas the tensile modulus is more consistent with micromechanical models assuming a uniform glass fiber distribution. Results from fractographic analyses show that the presence of matrix rich layers at the specimen surfaces may also lead to premature crack initiation and failure in flexion. [ABSTRACT FROM AUTHOR]

This article investigates the application of the luminescence spectroscopy technique in steady-state conditions to study the glass fiber-epoxy F155 prepreg. The study was conducted by comparing the results obtained from the intrinsic fluorescence with the data obtained by application of Fourier Transform Near Infrared spectroscopy (FT-NIR) and photoacoustic spectroscopy in the medium infrared spectroscopy (PAS) to the same material. Extrinsic fluorescence of 9-anthroic acid (9-AA) was also used. Infrared spectroscopy with Fourier transform the medium region (FT-IR) was also used to characterize the epoxy resin. Prepregs containing 9-AA or not were heat treated at 121 °C (F-155) for 360 min at a 2 °C/min heating rate. The results obtained by both methods indicated that the cross-linking reaction can be monitored by analyzing the spectrometric changes of the emission bands of the prepreg and 9-AA. The intrinsic emission at 368 nm was used to calculate the conversion degree. The photophysical behavior of 9-AA probe indicated a reduction of free volume of the polymeric matrix with curing process. [ABSTRACT FROM AUTHOR]

Up to now, poly- para-phenylene (PPP) can be considered as the stiffest and strongest polymer under ambient temperature conditions. As an amorphous thermoplastic, a thermal treatment will not change the material's morphology, but may influence its inner free volume (physical aging) and corresponding mechanical properties. This was investigated in this study with regard to the hardness and fracture toughness of PPP. It turned out that under the thermal conditions chosen, only moderate effects on these properties could be detected. Besides it was of interest how PPP compares in these properties relative to other advanced thermoplastics (neat and short glass fiber reinforced). Various features, such as striations and parabolic holes, on the fracture surfaces of PPP were also discussed. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer-matrix composites are known to exhibit loading rate- and time-dependent mechanical response. Their fatigue strength is determined by a complex interaction of damage processes governed by loading duration and cycle number. Apart from mechanistic approaches, a number of empirical models of various sophistication have been proposed to predict the durability of composites, differing in the amount of experimental data needed for their application. The accuracy of several such models is evaluated by comparing the prediction to the experimentally determined stress ratio effect on fatigue life of glass fiber-reinforced polyester-matrix composite. It is found that the accuracy of prediction generally improves with increasing the amount of test data needed for model calibration. However, the most accurate method of fatigue life estimation, among the selected ones, is by the modified Goodman diagram. [ABSTRACT FROM AUTHOR]

A letter about a study on unidirectional glass fiber-reinforced polymer (GFRP) composites is presented. The study utilized glass fibers that were modeled as a doubly periodic face-centered hexagonal array. It hypothesized that the polymeric fibrils of matrix stretched between the crack surfaces behave based on the Barenblatt cohesive force model.

The current work examines the durability of composites reinforced with glass fibre woven fabric as well as non-crimp fabrics (NCF) immersed in water at 43, 65 and 93 °C for up to 2.5 years. Low velocity normal impact has been induced at various time intervals before and after water immersion at energy levels of 2.5, 5 and 10 J. Following impact the plates were tested statically in compression to determine the residual strength for assessment of damage tolerance. The compression strength suffered significant reductions from the water absorption and the low velocity impact with values being dependent to the time of immersion and the water temperature. A parallel behaviour was monitored, in terms of strength reduction over time, of plates impacted prior to water immersion with the plates that contain no damage. For specimens where impact damage introduced after water immersion lower compression-after-impact (CAI) strength was observed at the same energy levels. An increase in damage diameter was evident, regardless the reinforcement type, though the gradually produced greater density of through thickness damage was responsible for the significant lower compression strength values. The presence of 0° fibres for the NCF composites as the main load bearing element dictated the sensitivity to impact as well as the corresponding residual strength. For composites with woven reinforcement, damage was contained and localized by the fabric weave and effective stress redistribution seemed to be the mechanism for the relatively higher residual strengths obtained. A semi-empirical model has been used with high accuracy in fitting the given experimental data and draw conclusions from the comparisons. [ABSTRACT FROM AUTHOR]

Rigid polyurethane foam (RPUF)/glass fiber composites have been fabricated from glass fiber, polymeric 4,4′-di-phenylmethane diisocyanate (PMDI) and polypropylene glycols (PPG) using HFC 365mfc as blowing agent. Thermal conductivity, glass transition and decomposition temperatures as well as the mechanical strengths of the foam increased with the addition of glass fiber. This indicates that an optimum fiber content should depend on the balance between the mechanical reinforcement and thermal insulation.The results were interpreted in terms of cell size, closed cell content, density, fiber dispersion and a simple series model for heat transfer of the composite foam. [ABSTRACT FROM AUTHOR]

The influence of annealing duration on the erosive wear behavior of short glass fiber (40% w/w) and CaCO3 mineral particulate (25% w/w)–short glass fiber (40% w/w) (total: 65% w/w) reinforced PPS composites has been characterized under various experimental conditions by differential scanning calorimetry (DSC) and erosion measurements. The erosive wear of the composites have been evaluated at different impingement angles (30, 45, 60, and 90°) and at four different annealing periods (30, 60, 90, and 120 min). Increase in the total crystallization causes an improvement in the erosive wear properties of the samples. Annealing time controls the morphology by influencing the degree of crystallinity in the matrix and in the fiber–matrix interface. This formation restricts fiber–matrix debonding. There is no linear proportionality between annealing time and relative degree of crystallization. The results indicate that PPS composites show maximum in wear versus impact angle relation at 60° confirming their semi-ductile failure behavior. The morphologies of eroded surface are examined by the scanning electron microscope. [ABSTRACT FROM AUTHOR]

Increasing concern for the environment has stimulated interest in the research and development of single polymer composite (SPC) materials. These materials are an emerging class of composite materials with mechanical properties comparable to heterogeneous composites. The SPCs are fully recyclable and have specific economic and environmental benefits. The small melting temperature difference between the fiber and the matrix poses a great challenge in the fabrication of SPCs. This article gives an overview of developments in SPCs relating to the materials and fabrication methods used. [ABSTRACT FROM AUTHOR]

The effects of ageing on the mechanical properties and thermal stresses distribution of injection moulded, short glass fibre/clay/polypropylene composites were studied. Two different clays were studied—talc and sepiolite. The results obtained indicate that the incorporation of short glass fibre into clay/polypropylene composites improves the mechanical properties, independently of ageing treatment. Larger elastic modulus values were obtained for talc-filled samples, whereas higher strength values were obtained with the sepiolite-filled ones. The impact strength increased as a result of the incorporation of glass fibre into the sepiolite-filled composite, while a small decrease was detected for the talc-filled polypropylene sample. Sepiolite-filled compounds show higher mould shrinkage in the bar-axis direction than equivalent talc-filled grades. In contrast, the shrinkage obtained on annealing at various temperatures between 100 and 160 °C was generally greater for talc-filled compounds than for the sepiolite-filled compounds. The shrinkage behaviour in the transverse direction was more complex. The residual stress levels of clay-filled polypropylene compounds were generally lower than those reported in the literature concerning short glass fibre polypropylene compounds under similar conditions. Hybrid composites showed much higher stress levels than the corresponding clay-filled samples independently of ageing conditions. [ABSTRACT FROM AUTHOR]

Entangled fibrous materials have been manufactured from different fibers: metallic fibers, glass fibers, and carbon fibers. Specimens have been produced with and without cross-links between fibers. Cross-links have been achieved using epoxy spraying. The scope of this article is to analyze the mechanical behavior of these materials and to compare it with available models. The first part of this article deals with entangled fibrous materials without cross-link between fibers. Compression tests are detailed and test reproducibility is checked. In the second part, compression tests were performed on materials manufactured with cross-linked fibers. The specific mechanical behavior obtained is discussed. [ABSTRACT FROM AUTHOR]

This paper evaluates the water absorption characteristics of glass fibre reinforced polymers after long-term exposure to a hygrothermal environment. In particular, three types of laminates, fabricated using woven and non-crimp triaxial glass fabric with a polyester matrix, were immersed in deionised water baths for 2.5 years (30 months) at temperatures of 43, 65 and 93 °C. In order to assess the effects of through-thickness delaminations on the water absorption characteristics, a series of specimens were impacted prior water immersion with low-velocity impact using three energy levels of 2.5, 5 and 10 J. The changes in the thermo-mechanical properties of laminates after water immersion were examined using the dynamic mechanical thermal analysis (DMTA) technique. The results revealed that the long-term water uptake profiles had no similarities to the classical Fickian absorption behaviour and they were markedly different for each water immersion temperature. At higher temperatures a multi-stage diffusion was observed, which was attributed to the microporosity of the laminates as well as to the osmotically enhanced uptake through the interfaces, with the peak values showing dependency on the type of material system. The impact damage on laminates immersed in water did not cause any marked change in the maximum water absorption level or at the absorption rate compared to the undamaged specimens. DMTA have shown matrix plasticizing effects at 43 °C and some post-curing effects at 65 and 93 °C while the effect of the time of immersion at all temperatures tested resulted in a decrease of the value of storage modulus. [ABSTRACT FROM AUTHOR]

In this paper, large-scale uniform silver and copper nano/microtubes with high length diameter ratios have been successfully synthesized by a facile approach, using low-cost nano-scale glass fibers as templates. The tubular structures can be obtained by reducing of Ag and Cu ions on the surface of the fibers, along with removing the templates. The samples are characterized by SEM and XRD. Results show the tubular structures are very uniform and the tubular walls are composed of densely coalesced crystalline nanoparticles of 30–50 nm. [ABSTRACT FROM AUTHOR]

The effect of fibre concentration, strain rate and weldline on tensile strength, tensile modulus and fracture toughness of injection-moulded thermoplastic polyurethane (TPU) reinforced with different concentration levels of short glass fibres was investigated. It was found that tensile strength, σc, of single-gated mouldings increased with increasing volume fraction of fibres, ϕf, according to a second order polynomial function of the form $$ \sigma_{\text{c}} = a_{0} + a_{1} \phi_{\text{f}} + a_{2} \phi_{\text{f}}^{2} $$ and increased linearly with natural logarithm of strain rate ( $$ { \ln }\,\dot{e} $$). Tensile modulus and fracture toughness (at initiation) of single-gated mouldings increased linearly with increasing ϕf (rule-of-mixtures) and $$ { \ln }\,\dot{e} $$. A linear dependence was obtained between fibre efficiency parameter for composite modulus, ηE, and $$ { \ln }\,\dot{e} $$. The presence of weldline in double-gated mouldings reduced tensile strength, tensile modulus and fracture toughness of TPU composites but had no significant effect upon properties of the TPU matrix. All the aforementioned properties increased with increasing fibre concentration and showed a linear dependence with respect to $$ { \ln }\,\dot{e} $$. Weldline integrity factor for all three properties decreased with increasing fibre concentration showing no strain-rate effect of any significance. Results indicated that tensile strength was more affected by the presence of weldline than tensile modulus or fracture toughness. It was noted that composite properties in the presence of weldline were still much greater than those for the unweld matrix. Weldline integrity values close to unity indicated that measured properties for the matrix were not significantly affected by the weldline. [ABSTRACT FROM AUTHOR]