Effect of structure on mechanical properties of vinyl ester resins and their glass fiber‐reinforced composites

The article describes the effect of structure of vinyl ester resins (VE) on the mechanical properties of neat sheets as well as glass fabric‐reinforced composites. Different samples of VE were prepared by reacting ester of hexahydrophthalic anhydride (ER) and methacrylic acid (MAA) (1 : 1 molar ratio) followed by reaction of monomethacrylate terminated epoxy resin with glutaric (E) or adipic (F) or sebacic acid (G) (2 : 1 molar ratio). The neat VE were diluted with styrene and sheets were fabricated by using a glass mold. A significant reduction in the mechanical properties was observed by increasing the methylene content of resin backbone (i.e., sample E to G). Glass fabric‐reinforced composites were fabricated by vacuum assisted resin transfer molding (VARTM) technique. Resin content in the laminates was 50 ± 5 wt %. Increase in the number of methylene groups in the vinyl ester resin (i.e., increasing the bridge length) did not show any significant effect on limiting oxygen index (LOI) value (21 ± 1) of the laminates but tensile strength, tensile modulus, flexural strength, and flexural modulus all increased though these values are significantly lower than observed in laminates based on resin B. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites

The incorporation of natural fibers with polymer matrix composites (PMCs) has increasing applications in many fields of engineering due to the growing concerns regarding the environmental impact and energy crisis. The objective of this work is to examine the effect of fiber orientation and fiber content on properties of sisal‐jute‐glass fiber‐reinforced polyester composites. In this experimental study, sisal‐jute‐glass fiber‐reinforced polyester composites are prepared with fiber orientations of 0° and 90° and fiber volume of sisal‐jute‐glass fibers are in the ratio of 40:0:60, 0:40:60, and 20:20:60 respectively, and the experiments were conducted. The results indicated that the hybrid composites had shown better performance and the fiber orientation and fiber content play major role in strength and water absorption properties. The morphological properties, internal structure, cracks, and fiber pull out of the fractured specimen during testing are also investigated by using scanning electron microscopy (SEM) analysis. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42968.     

Investigation of mechanical properties of alumina nanoparticle‐loaded hybrid glass/carbon‐fiber‐reinforced epoxy composites

This research work investigates the tensile strength and elastic modulus of the alumina nanoparticles, glass fiber, and carbon fiber reinforced epoxy composites. The first type composites were made by adding 1–5 wt % (in the interval of 1%) of alumina to the epoxy matrix, whereas the second and third categories of composites were made by adding 1–5 wt % short glass, carbon fibers to the matrix. A fourth type of composite has also been synthesized by incorporating both alumina particles (2 wt %) and fibers to the epoxy. Results showed that the longitudinal modulus has significantly improved because of the filler additions. Both tensile strength and modulus are further better for hybrid composites consisting both alumina particles and glass fibers or carbon fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39749.     

High‐temperature tensile behavior at different crosshead speeds during loading of glass fiber‐reinforced polymer composites

The present study evaluates on the static tensile behavior of glass fiber reinforced polymer (GFRP) composites at 50% and 70% volume fractions of reinforcement tested at room (25 °C), 70 °C, 90 °C, and 110 °C temperatures with 1, 10, 100, 500, and 1000 mm/min crosshead speeds to investigate the impact of high temperature on the mechanical properties and different dominating failures modes. The experimental results reveal that with increase in crosshead speeds the tensile strength of the composite is increasing. The effect of crosshead speeds and temperature with changing fiber volume fractions affects the GFRP composite. Although both the composite systems are found to be crosshead speed sensitive. Crosshead speed sensitivity seems to be more unpredictable at high temperature and at high crosshead speed. Furthermore, it appears to be more unprecedented nature of fluctuation with high fiber volume fraction. The crucial parameters required during the materials designing in various structural components were evaluated and modelled with the help of Weibull constitutive model. The fractography analyses were done to identify the various dominating failure modes in the GFRP composite. There was no significant change found in the glass transition temperatures (T_g) of both the composite system when exposed to different temperature environments. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44715.     

Short sisal fiber‐reinforced tire rubber composites: Dynamic and mechanical properties

The world tendency toward using recycled materials demands new products from vegetable resources and waste polymers. In this work, composites made from powdered tire rubber (average particle size: 320 μm) and sisal fiber were prepared by hot‐press molding and investigated by means of dynamic mechanical thermal analysis and tensile properties. The effects of fiber length and content, chemical treatments, and temperature on dynamic mechanical and tensile properties of such composites were studied. The results showed that mercerization/acetylation treatment of the fibers improves composite performance. Under the conditions investigated the optimum fiber length obtained for the tire rubber matrix was 10 mm. Storage and loss moduli both increased with increasing fiber content. The results of this study are encouraging, demonstrating that the use of tire rubber and sisal fiber in composites offers promising potential for nonstructural applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 670–677, 2004     

Microstructural investigation of butt‐fusion joint in high‐density polyethylene pipes using wide‐ and small‐angle X‐ray scattering

The melt fusion zone (MFZ) of polyethylene pipe was investigated employing synchrotron wide‐ and small‐angle X‐ray scattering at various locations in MFZ by changing X‐ray incidence angles to probe three‐dimensional structural features. It was determined that the crystals were oriented in two different modes. One is that the polymer chains are oriented parallel to the joint interface line consistently throughout the MFZ. The other is that the crystals are oriented in particular directions depending on the positions in MFZ. The combination of pressure and melt flow during joining process resulted in such a complex structure. It was notable that the boundary of MFZ against the base material was found to be very different depending on the structures involved such as crystallographic unit orientation, lamellae orientation, crystallinity, and spherulitic morphology. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45668.     

The effect of fiber concentration on mechanical and thermal properties of fiber‐reinforced polypropylene composites

A novel composite material consisting of polypropylene (PP) fibers in a random poly(propylene‐co‐ethylene) (PPE) matrix was prepared and its properties were evaluated. The thermal and mechanical properties of PP–PPE composites were studied by dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC) with reference to the fiber concentration. Although, by increasing PP fiber concentration in PPE, no significant difference was found in melting and crystallization temperatures of the PPE, the storage, and the tensile and flexural modulus of the composites increased linearly with fiber concentrations up to 50%, 1.5, 1.0, 1.3 GPa, respectively, which was approximately four times higher than that for the pure PPE. There is a shift in glass transition temperature of the composite with increasing fiber concentration in the composite and the damping peak became flatter, which indicates the effectiveness of fiber–matrix interaction. A higher concentration of long fibers (>50% w/w) resulted in fiber packing problems, difficulty in dispersion, and an increase in void content, which led to a reduction in modulus. Cox–Krenchel and Haplin–Tsai equations were used to predict tensile modulus of random fiber‐reinforced composites. A Cole–Cole analysis was performed to understand the phase behavior of the composites. A master curve was constructed based on time–temperature superposition (TTS) by using data over the temperature range from −50 to 90°C, which allowed for the prediction of very long and short time behavior of the composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2260–2272, 2005     

Carbon fiber‐reinforced gelatin composites. I. Preparation and mechanical properties

Composites were made from carbon fibers and gelatin using a solvent‐casting or solution‐impregnation technique. Relationships between the fiber volume fraction (Vf), glycerol (plasticizer) content, gelatin content, fiber form, and mechanical properties (tensile strength and modulus, elongation at break, and shear strength) of the composites were investigated. In long carbon fiber gelatin composite (C_L/Gel), tensile strength, modulus, and shear strength increased steadily with the Vf. In the case of a short carbon fiber gelatin composite (C_S/Gel), an initial improvement in tensile strength and modulus was followed by a reduction, whereas the shear strength improved with the Vf and then reached a constant value. The elongation decreased with the Vf for both composites. It is shown that C_L/Gel had higher values of strength, modulus, and elongation than did C_S/Gel at any Vf level. The effects of glycerol and gelatin contents on the mechanical properties of the composites were found to be much less significant as compared to the Vf. According to scanning electron microscopic observation of the fracture surfaces, the fibers were uniformly distributed in the gelatin matrix, but the interfacial adhesion between the gelatin matrix and the carbon fibers was not very good for both composites. Fiber surface modification would be necessary to further improve the mechanical properties of the two composites. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 987–993, 2000     

Crystallization,mechanical, and fracture behavior of mullite fiber‐reinforced polypropylene nanocomposites

This study describes the reinforcement effect of surface modified mullite fibers on the crystallization, thermal stability, and mechanical properties of polypropylene (PP). The nanocomposites were developed using polypropylene‐grafted‐maleic anhydride (PP‐g‐MA) as compatibilizer with different weight ratios (0.5, 1.0, 1.5, 2.5, 5.0, and 10.0 wt %) of amine functionalized mullite fibers (AMUF) via solution blending method. Chemical grafting of AMUF with PP‐g‐MA resulted in enhanced filler dispersion in the polymer as well as effective filler‐polymer interactions. The dispersion of nanofiller in the polymer matrix was identified using scanning electron microscopy (SEM) elemental mapping and transmission electron microscopy (TEM) analysis. AMUF increased the Young's modulus of PP in the nanocomposites up to a 5 wt % filler content, however, at 10 wt % loading, a decrease in the modulus resulted due to agglomeration of AMUF. The impact strength of PP increased simultaneously with the modulus as a function of AMUF content (up to 5 wt %). The mechanical properties of PP‐AMUF nanocomposites exhibited improved thermal performance as compared to pure PP matrix, thus, confirming the overall potential of the generated composites for a variety of structural applications. The mechanical properties of 5 wt % of AMUF filled PP nanocomposite were also compared with PP nanocomposites generated with unmodified MUF and the results confirmed superior mechanical properties on incorporation of modified filler. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43725.     

Preparation and mechanical properties of high‐performance short ramie fiber‐reinforced polypropylene composites

Short ramie fiber (RF) was used to reinforce the polypropylene (PP). The composites were prepared in a twin‐screw extruder followed by injection molding. The experimental results showed that both the strength and the modulus of the composites increase considerably with increasing RF content. The tensile strength and flexural strength are as high as 67 and 80 MPa by the incorporation of ramie up to 30 wt %. To the best of our knowledge, this is one of the best results for short natural fiber‐reinforced PP composites. However, the preparation method in this study is more simple and economic. This short RF‐reinforced PP composites extend the application field for short‐nature fiber‐reinforced PP composites. Morphological analysis revealed that it is the high aspect ratio of the fiber and good interfacial compatibility that result in the high performance of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Development of high Tg epoxy resin and mechanical properties of its fiber‐reinforced composites

A new epoxy resin with high glass transition temperature (T_g) (～ 180°C) and a viscosity low enough for infiltration into dry reinforcements at 40°C was developed for the vacuum‐assisted resin transfer molding process. To study the curing behavior and viscosity, several blends were formulated using multifunctional resin, aromatic hardener, and reactive diluents. Effects of these components on the viscosity and T_g were investigated by thermomechanical analysis, dynamic scanning calorimetry, and rheometer. Experimental results showed that a liquid aromatic hardener and multifunctional epoxy resin should be used to decrease the viscosity to <1 Pa·s at 40°C. Moreover, the addition of a proper reactive diluent decreased the viscosity and simultaneously minimized the deterioration of T_g. Mechanical properties of the composite produced with the optimized blend were evaluated at both room‐temperature and high‐temperature conditions. According to the results, the composite showed comparable mechanical properties with that of the current commercial resin. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Performance and mechanism of laser transmission joining between glass fiber‐reinforced PA66 and PC

On account of the large compatibility difference between glass fiber‐reinforced Polyamide 66 (GFR‐PA66) and Polycarbonate (PC), it is difficult to weld them directly by laser. A new technology is introduced in this article by which the transparent PC is successfully welded with GFR‐PA66 using cold spraying in order to spray a 20 μm‐thick aluminum film on GFR‐PA66 as the absorbed layer. Tensile shear tests show the tensile strength of welded joints is highly enhanced. The influences of bubbles, glass fiber, and aluminum atoms on the performance of the joins are investigated via the optical microscope. X‐ray Photoelectron Spectrometer (XPS) is used to detect the chemical information of fracture sections on PC. In terms of the generation of bubbles, the influence of glass fiber, the distribution of aluminum atoms, and the formation of new chemical bonds, this article analyses the mechanism why the two different materials can be welded successfully. The micro‐anchor influence of glass giber in fiber‐reinforced polymers is important. The generation of new chemical bonding (Al–O–C) between aluminum and upper PC is the main reason why the joining strength is enhanced greatly. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43068.     

Fabrication and mechanical properties of glass fiber‐reinforced wood plastic hybrid composites

To fully utilize the resource in the municipal solid waste (MSW) and improve the strength and toughness of wood plastic composites, glass fiber (GF)‐reinforced wood plastic hybrid composites (GWPCs) were prepared through compounding of recycled high‐density polyethylene (HDPE) from MSW, waste wood fibers, and chopped GF. Mechanical tests of GWPCs specimens with varying amounts of GF content were carried out and the impact fractured surface of GWPCs was observed through scanning electron microscope (SEM). The tensile strength of GWPCs and the efficiency coefficient values were predicted by Kelly‐Tyson method. The results indicated that the tensile strength and impact strength of GWPCs could be improved simultaneously by adding type L chopped GF (L‐GF), and would be dropped down when type S chopped GF (S‐GF) was included. The tensile strength of GWPCs was well accordant with the experimental result. The efficiency coefficient values of S‐GF and L‐GF are ?0.19 and 0.63, respectively. Inspection of SEM micrographs indicated that L‐GF had achieved full adhesion with the plastic matrix through addition of maleic anhydride‐g‐polyethylene. The main fracture modes of GWPCs included pullout of GF, broken of matrix, and interfacial debonding. Because of the synergistic effects between hybrid components in GF/wood fiber/HDPE hybrid system, a special 3D network microstructure was formed, which was the main contribution to the significant improvement in the tensile strength and impact strength of L‐GF‐reinforced hybrid composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Carbon‐fiber‐reinforced acrylonitrile–styrene–acrylate composites: Mechanical and rheological properties and electrical resistivity

The aim of this study was to improve the mechanical properties of an acrylonitrile–styrene–acrylate copolymer (ASA) with the help of carbon fibers (CFs). Additionally, the effects of the CFs on the morphology, rheological properties, dynamical mechanical properties, electrical resistivity, and heat resistance of the ASA composites were studied with scanning electron microscopy, rotational rheometry, and dynamic thermomechanical analysis (DMA). The mechanical properties of the ASA composites were enhanced largely by the CFs. The maximum tensile strength of the ASA/CF composites reached 107.2 MPa. The flexural strength and flexural modulus also reached 162.7 MPa and 12.4 GPa, respectively. These findings were better than those of neat ASA; this was attributed to the excellent interfacial adhesion between the CFs and ASA resin. Rheological experiments proved that the viscosity and storage modulus (G′) values of the ASA/CF composites did not increase until the CF content reached 20%. The DMA outcomes confirmed that the glass‐transition temperature of the ASA composites was elevated from 120.6 to 125°C. Importantly, the G′ values of the composites with 20 and 30% CFs showed a large increase during heating. In addition, the ASA/CF composites exhibited excellent conductivity and heat resistance. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43252.     

Morphology,thermal and mechanical properties of glass fiber‐reinforced crosslinkable poly(arylene ether nitrile)

Crosslinkable poly(arylene ether nitrile)/glass fiber (PEN/GF) composites with high thermal stabilities and mechanical properties were prepared by a economically and environmentally viable method of melt extrusion and injection molding. The feasibility of using PEN/GF composites was investigated by evaluating its morphological, rheological, thermal, and mechanical properties. The morphology shows a good dispersion and strong interfacial interaction between PEN and GF. Thermal studies reveal that the thermal stabilities of PEN/GF are improved significantly with increase of GF content. Mechanical investigation manifested that GFs have strengthening effect (increase in flexural, tensile, and impact strength) on the mechanical performance of PEN composites. Most importantly, crosslinking reaction of PEN/GF composites can further improve their mechanical performances, because a couple of GFs are agglomerated by thermal motion and strong interfacial adhesion and the local agglomeration does not break the global uniform distribution. This work shows that both the enhancement of GF content and the crosslinking reaction of PEN/GF composites are two key factors influencing the thermal and mechanical properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Properties and applications of nanoclay reinforced open‐porous polymer composites

Open‐porous nanoclay reinforced polymer composites were prepared via high internal phase emulsion templating using 1,3‐butanediol dimethacrylate and surface modified montmorillonite (SM‐MMT). Organophilic clay was obtained by using a reactive intercalant—quaternary cocoamine salt having a styryl group—for surface modification of MMT. The clay modification resulted in not only intercalated silicate layers but also nanoclay particles compatible with the continuous phase of the emulsions. It was found that increasing clay amount leads to formation of hierarchical porous structure accompanied with larger cavities and interconnected pores. In this respect, cavity size of the resulting composites was found to be altered between 6.78 and 8.82 μm. On the other hand, as compared to bare composites, addition of clay particles increased compressive modulus of the resulting materials from 26.4 to 72.5 MPa. The adsorption capacities of the porous composites for methyl violet 2B were investigated by batch experiments and discussed as a function of their SM‐MMT loading. It was determined that, the dye adsorption of the composites increased with increasing nanoclay amount in the polymer matrix. Thus, the adsorption percentage of the composite loaded with 7 wt % nanoclay was found to be as high as 88%. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45522.     

Heat‐damage assessment of carbon‐fiber‐reinforced polymer composites by diffuse reflectance infrared spectroscopy

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to assess the effects of heat damage on carbon‐fiber‐reinforced polymer composites. Moisture‐saturated graphite–epoxy laminates with a quasi‐isotropic lay‐up were heat‐damaged above their upper service temperatures. The loss of matrix‐dominated mechanical properties due to heat exposure was investigated in the laboratory under environmental testing conditions with mechanical tests, ultrasonic C‐scanning, and DRIFT spectroscopy. The reduction of the mechanical strength of the composite materials was accompanied by an increase in the carbonyl band integral and a decrease in the phenyl ratio and hydroxyl and hydrocarbon band integrals, as shown by the DRIFT spectra. DRIFT was confirmed to be more effective than ultrasonic inspection in evaluating the extent of heat damage, and a good correlation was found between the mechanical test results and DRIFT spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1222–1230, 2005     

Self‐welding 1‐butene/ethylene copolymers from metallocene catalysts: Structure,morphology, and mechanical properties

Samples of random copolymers consisting of 1‐butene modified with a low ethylene content (4, 5, 8% by weight) produced with metallocene catalysts were studied to elucidate the polymorphic behavior of this new class of materials and to characterize them from a structural, morphological, and mechanical point of view. The samples cooled down from the melt are in amorphous phase and crystallize in a mixture of form I and I′ or in pure form I′ with aging time, according to the C2 content. Infrared and nuclear magnetic resonance spectroscopy, X‐ray diffraction and microscopic techniques were used to follow the changes of the material with aging time and to correlate the structural and morphological behavior with the peculiar mechanical properties that differentiate the samples with increasing C2 content. The presence, in the aged samples with higher C2 content, of the pure form I′ induces the peculiar ability to self‐welding and these copolymers combine high flexibility with good elasticity and ductility and can be processed directly or used as modifying agents in polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40119.     

The mechanical and tribological properties of nitric acid‐treated carbon fiber‐reinforced polyoxymethylene composites

The carbon fibers have been exposed to nitric acid oxidation treatments and introduced into polyoxymethylene composites (POM/CF). The nitric acid treatment increases the number of the flaws, roughness of the surface, and disorder of carbon atoms on fiber, as well as introduces reactive functional groups, which could lead to a better mechanical bonding between fiber and the matrix. It is shown that the impact strength and fiber‐matrix adhesion in composites (POM/mCF) are superior to those for POM/CF composites. Simultaneously, the addition of mCF improves flexural strength and modulus relative to virgin POM significantly. Average friction coefficient values of POM/CF composites are lower than that of POM/mCF composites. As the percentage of fiber increases, the trend of wear ratio of the composites goes down initially and bumps up afterwards. The results indicate that the proper contents of CF and mCF in composites range from 5 wt % to 20 wt %. Scanning electron microscopy of worn surface morphology has revealed that the main wear mechanism of the composites were adhesive wear and ploughing wear. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41812.     

Effect of thermal shock on interlaminar strength of thermally aged glass fiber‐reinforced epoxy composites

Glass fiber/epoxy composites were thermally conditioned at 50, 100, 150, 200, and 250°C for different periods of time and then immediately quenched directly in ice‐cold water from each stage of conditioning temperature. The polymerization or depolymerization by thermal conditioning and the debonding effect by concurrently following thermal shock in polymer composites are assessed in the present study. The short‐beam shear tests were performed at room temperature on the quenched samples to evaluate the value of interlaminar shear strength of the composites. The short conditioning time followed by thermal shock resulted in reduction of shear strength of the composites. The strength started regaining its original value with longer conditioning time. Conditioning at 250°C and thereafter quenching yielded a sharp and continuous fall in the shear strength. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2062–2066, 2006