Impact behavior of unidirectional polyethylene–glass fibers: PMMA hybrid composite laminates

Unidirectional (UD) hybrid laminates based on glass fibers (GF) and high performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature followed by heating at 55°C (well below the softening point of PEF) for 2 h. Izod impact strength of the composites was then measured. An interesting observation of the study was the change in impact strength that was largely dependent on the position of GF and PEF ply/plies present within the hybrid laminates. When the ply/plies of PEF were at the impacted surface, the impact strength showed a higher value than that of the case when GF ply/plies were at the impacted surface of the hybrid laminates. © 1996 John Wiley & Sons, Inc.     

Tensile behavior of unidirectional polyethylene fibers PMMA and glass fibers—PMMA composite laminates

Unidirectional (UD) composite laminates based on glass fibers (GF) and high‐performance polythylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF) for 2 h. The tensile strength, modulus of elasticity, fiber efficiency and strength efficiency of both the composite laminates, loaded parallel to the fibers, at the same volume fraction range, were investigated. All the properties were compared between the two composite laminates. It was observed that the measured tensile strength and modulus of elasticity deviated from the values calculated from the Rule of Mixture (ROM). The deviation was minimal at the lower volume fraction of fibers, and increased with the fiber volume. An interesting feature that was observed was that the efficiencies of PEF‐reinforced composite was higher than that of the GF‐reinforced composite at the same volume fraction of the fibers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1489–1493, 2000     

Dynamic mechanical study on unidirectional polyethylene fibers-PMMA and glass fibers-PMMA composite laminates

Unidirectional (UD) composite laminates based on glass fibers (GF) and high-performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at room temperature and then heated at 55°C (well below the softening point of PEF) for 2 hrs. The viscoelastic behavior of the composite was studied through dynamic mechanical analysis at different volume fractions of fibers. Several parameters such as storage modulus (E′), loss modulus (E″), and loss factor or damping efficiency (tan ∂) were determined to be between 40 and 160°C in a resonant frequency mode. All the properties were compared between the two composite laminates. It was found that the shift of the glass transition temperature (T_g) due to incorporating fibers was higher in the case of a PEF-reinforced composite than that of a GF-reinforced composite at the same volume fraction of fibers. It was also observed that the efficiency of both the composites decreases with the increase in the volume fraction of fibers. © 1996 John Wiley & Sons, Inc.     

Dynamic mechanical study on unidirectional polyethylene–carbon fibers: PMMA hybrid composite laminates

Unidirectional (UD) composite laminates based on carbon fibers (CF) and high-performance polyethylene fibers (PEF) were prepared with partially polymerized methyl methacrylate (MMA) at 25°C, followed by heating at 55°C (well below the softening point of PEF) for 2 h. The viscoelastic behavior of the composite was studied through dynamic mechanical analysis at different volume fractions of the fibers. Several parameters such as the storage modulus (E′), loss modulus (E′), and loss factor or damping efficiency (tan δ) were determined between 40 and 160°C in a resonant frequency mode. The glass transition temperature (T_g) increased to a higher region with increase in the volume of PEF in the hybrid laminates. It was also observed that the efficiency of the composite decreases with increase in the volume fraction of the fibers. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1631–1637, 1998     

Stress-relaxation behavior of unidirectional polyethylene–carbon fibers: PMMA hybrid composite laminates

Unidirectional composite laminates based on carbon fibers (CF) and high-performance polyethylene fibers (PEF) and their hybrids were prepared with partially polymerized methyl methacrylate (MMA) at room temperature, followed by heating at 55°C (well below the softening point of PEF, 147°C) for 2 h. The stress-relaxation behavior of the composites were determined and analyzed. It was found that at all strain levels the rate of stress relaxation decreased by the loading of CF in CF-reinforced composite laminates (CFRC); however, the reverse behavior was found in the case of PEF-reinforced composite laminate (PEFRC). An interesting observation of the study was that the rate of stress relaxation decreased linearly in two steps in the case of PEFRC, whereas in the case of CFRC, it decreased in a single step. In the case of hybrid composites, the stress relaxation decreases in two steps as in PEFRC. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1925–1929, 1998     

Impact behavior of unidirectional polyethylene–glass fibers: Resol/vinyl acetate‐2‐ethylhexylacrylate interpenetrating polymer network systems

Resol was solution blended with vinyl acetate‐2‐ethylhexylacrylate (VAc–EHA) resin in an aqueous medium at a 90‐10 w/w ratio with hexamethoxymethylmelamine (HMMM) as crosslinker. Here we aimed to study the impact behavior of unidirectional laminates cast from (Resol/VAc–EHA/HMMM)/glass fiber (GF), (Resol/VAc–EHA/HMMM)/polyethylene fiber (PEF), and (Resol/VAc–EHA/HMMM)/GF/PEF (hybrid) and to study the role of PEF ply/plies in hybrid laminates toward the impact behavior, as dependent on the relative position of the ply/plies. A brittle failure mode was observed in the GF‐reinforced laminates, which tended to the ductile failure mode, with the incorporation of PEF ply/plies. Again, the impact fracture mode of GF was minimized by the placement of PEF ply/plies at the impacted side of the hybrid laminates. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 339–342, 2004     

Designing a low-temperature curable phenolic/benzoxazine-functionalized phthalonitrile copolymers for high performance composite laminates

A low-temperature curable phenolic/benzoxazine-functionalized phthalonitrile (SH/BZ-CN) copolymer system with well processability is designed and applied in high performance glass fiber (GF) composite laminates. Differential scanning calorimetry (DSC) results showed that plenty of phenolic hydroxyl groups on SH could catalyze the oxazine ring-opening and triazine/phthalonitrile ring-forming reaction of BZ-CN. The ring-opening peak and ring-forming peak of SH/BZ-CN systems are reduced by 47.1 °C and 17.0 °C than those of BZ-CN, respectively. The processability of SH/BZ-CN copolymers were improved and could be controlled by tuning SH content, processing temperature and time. These parameters provided ground for preparing SH/BZ-CN/GF composite laminates under a relatively mild condition. All SH/BZ-CN/GF composite laminates exhibit excellent flexural strength more than 500 MPa and flexural modulus over 22.0 Gpa. SH/BZ-CN/GF composites showed immiscible structures and double Tgs, and they could stand high temperature up to 350 °C. Low temperature curing, short processing time and low processing pressure are beneficial to large-scale manufacturing and application of SH/BZ-CN/GF composites.     

Effect of ortho‐diallyl bisphenol A on the processability of phthalonitrile‐based resin and their fiber‐reinforced laminates

Sluggish and narrow process window of phthalonitrile resin has tremendously limited their wide applications. In this work, a novel phthalonitrile containing benzoxazine (4,4′‐(((propane‐2,2‐diylbis (2H‐benzo [e] [1,3]oxazine‐6,3 (4H)‐diyl) bis(3,1‐phenylene))bis(oxy)) diphthalonitrile, BA‐ph) with ortho‐diallyl bisphenol A (DABPA) was investigated. The processing window of the BA‐ph/DABPA blends were found from 50°C to 185°C, which was significantly broader than that of the pure BA‐ph (120–200°C). The composites were prepared through a curing process involving sequential polymerization of allyl moieties, ring‐opening polymerization of oxazine rings and ring‐forming polymerization of nitrile groups. BA‐ph/DABPA/GF(glass fiber) composite laminates were prepared in this study, and the composite laminate with BA‐ph/DABPA molar ratio of 2/2 showed an outstanding flexural strength and modulus of 560 MPa and 37 GPa, respectively, as well as a superior thermal and thermo‐oxidative stability up to 408 and 410°C. These outstanding properties suggest that the BA‐ph/DABPA/GF composites are suitable candidates as matrices for high performance composites. POLYM. ENG. SCI., 56:150–157, 2016. © 2015 Society of Plastics Engineers     

Electrically conductive composites based on epoxy resin containing polyaniline–DBSA‐ and polyaniline–DBSA‐coated glass fibers

Four kinds of polyaniline (PANI)‐coated glass fibers (GF–PANI) combined with bulk PANI particles were synthesized. GF–PANI fillers containing different PANI contents were incorporated into an epoxy–anhydride system. The best conductivity behavior of the epoxy/GF–PANI composites was obtained with a GF–PANI filler containing 80% PANI. Such a composite shows the lowest percolation threshold at about 20% GF–PANI or 16% PANI (glass fiber‐free basis). The PANI‐coated glass fibers act as conductive bridges, interconnecting PANI particles in the epoxy matrix, thus contributing to the improvement of the conductivity of the composite and the lower percolation threshold, compared with that of a epoxy/PANI–powder composite. Particularly, the presence of glass fibers significantly improves the mechanical properties, for example, the modulus and strength of the conductive epoxy composites. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1329–1334, 2004     

Carbon fiber reinforced melamine‐formaldehyde

New composites based on carbon fiber (cf) and melamine‐formaldehyde (MF) are presented. Composites were manufactured by pressing stacked planar random veils (webs) or unidirectionally (UD) arranged fibers, and MF impregnated thin cellulose sheets. Non‐vented pressing for 60 s was used. Also, planar random, UD and bidirectional fiber composites with or without alumina trihydrate (ATH) were manufactured by conventional compression molding using much longer times (up to 20 min). Tensile strength of about 500 MPa and stiffness of 60 GPa was obtained for the UD composite containing 23 vol% fiber, and no ATH. Practically the same strength was measured for the bidirectional composite containing 46 vol% fiber and no ATH. Tensile strength and modulus of 130 MPa and 28 GPa, respectively, was obtained for the random fiber composite containing 16 vol% fiber. Measurements showed that replacement of ATH with cellulose in a composite containing 6 vol% carbon fibers increased the strength (2.5 times) without any penalty on stiffness, and increased strain at break. Cf‐MF interfacial strength is low. This was estimated for clean fibers by means of transverse tensile testing and in‐situ scanning electron microscopy (SEM), and for fibers with an epoxy compatible coating by using the interlaminar shear strength (ILSS) test. The cf/MF/cellulose composite performed well up to 200°C. Within this temperature range it retained 80% of its stiffness compared to about 60% in the case of a representative epoxy with a higher content of carbon fibers.     

Preparation and properties of bisphenol A‐based bis‐phthalonitrile composite laminates

A series of bisphenol A (BPA)‐based 2,2‐bis‐[4‐(3,4‐dicyanophenoxy)phenyl]propane (BAPh) prepolymers and polymers were prepared using BPA as a novel curing agent. Ultraviolet–visible and Fourier transform infrared spectroscopy spectrum were used to study the polymerization reaction mechanism of the BAPh/BPA polymers. The curing behaviors were studied by differential scanning calorimetry and dynamic rheological analysis, the results indicated that the BAPh/BPA prepolymers exhibit large processing windows (109.5–148.5°C) and low complex viscosity (0.1–1 Pa·s) at moderate temperature, respectively. Additionally, the BAPh/BPA/glass fiber (GF) composite laminates were manufactured and investigated. The flexural strength and modulus of the composite laminates are 548.7–632.8 MPa and 25.7–33.2 GPa, respectively. The thermal stabilities of BAPh/BPA/GF composite laminates were studied by thermogravimetry analysis. The temperatures at 5% weight loss (T_5%) of the composite laminates are 508.5–528.7°C in nitrogen and 508.1–543.2°C in air. In conclusion, the BAPh/BPA systems can be used as superior matrix materials for numerous advanced composite applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Design of the phthalonitrile‐based composite laminates by improving the interfacial compatibility and their enhanced properties

Phthalonitrile containing benzoxazine (BA‐ph) and cyanate ester (CE) were chosen as the thermosetting matrix and the glass fiber (GF) reinforced laminates formed at low temperature were designed. The polyarylene ether nitriles containing pendent carboxyl groups (CPEN) was selected to modify the interfacial interaction between the resin matrix and GFs. Two methods of introducing CPEN were compared and the effects of CPEN on curing behaviors and properties of the composites were investigated. Results showed that with the CPEN, exothermic peaks shifted to lower temperature and curing temperatures of BA‐ph/CE decreased slightly. The mechanical and thermal properties of GF‐reinforced composites were discussed and the results indicated that the composites of modified GFs with CPEN exhibited outstanding mechanical properties, higher glass transition temperature (T_g > 290 °C) than that of composites composed of CPEN mixed with BA‐ph/CE. Moreover, GF‐reinforced composites showed stable dielectric constants (3.8–4.5) and low dielectric loss (0.005–0.01), which were independent of the frequency. In sum, the various methods of the introduction of CPEN in the GF‐reinforced composites may provide a new route to prepare improved composites, meanwhile, composites with outstanding processability and excellent mechanical and thermal properties are expected to be widely applied in the fields of high‐performance structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45881.     

Mechanical,thermal, electrical,and interfacial properties of high‐performance bisphthalonitrile/polyarylene ether nitrile/glass fiber composite laminates

Bisphthalonitrile (BAPh)/polyarylene ether nitrile end‐capped with hydroxyl groups (PEN‐OH) composite laminates reinforced with glass fiber (GF) have been fabricated in this article. The curing behaviors of BAPh/PEN‐OH prepolymers have been characterized by differential scanning calorimetry and dynamic rheological analysis. The results indicate that with the introduction of PEN‐OH the curing temperature of BAPh has decreased to 229.6–234.8°C and BAPh/PEN‐OH prepolymers exhibit large processing windows with relatively low melt viscosity. The BAPh/PEN‐OH/GF composite laminates exhibit tensile strength (272.4–456.5 MPa) and modulus (4.9–10.0 GPa), flexural strength (507.1–560.9 MPa), and flexural modulus (24.0–30.4 GPa) with high thermal (stable up to 538.3°C) and thermal stabilities (stable up to 475.5°C). The dielectric properties of BAPh/PEN‐OH/GF composite laminates have also been investigated, which had little dependence on the frequency. Meanwhile, scanning electron microscopy results show that the BAPh/PEN‐OH/GF composite laminates display excellent interfacial adhesions between the matrix and GFs. Herein, the BAPh/PEN‐OH matrix can be a good matrix for high‐performance polymeric materials and the advanced BAPh/PEN‐OH/GF composite laminates can be used under high temperature environment. POLYM. COMPOS., 34:2160–2168, 2013. © 2013 Society of Plastics Engineers     

Influence of thermo‐oxidative aging on the dynamical mechanical properties and thermal degradation kinetics of glass fiber‐reinforced PA10T composites

Unveiling the fundamental thermal‐oxidative aging mechanism and thermal degradation kinetics of the poly(decamethyleneterephthalamide) (PA10T)/ glass fiber (GF) composites under different aging temperatures (160°C, 200°C, and 240°C) for 0–50 days will facilitate the understanding of the interaction between matrix PA10T and GF. The results revealed that the decrease of mechanical properties referring to tensile strength, flexural strength and notched impact strength, and the occurrence of debonding phenomenon between PA10T matrix and GF were increasingly obvious after longer aging time at higher aging temperature. At the same time, the decline of crystalline was mainly ascribed to the thermal‐oxidative aging effect, which triggered the deterioration of mechanical properties of PA10T/GF composites. Accordingly, the enhancement of rigidity were probably attributed to the higher temperature aging effect with the aging time prolonging in PA10T/GF composites, while the interfacial debonding between GF and resin matrix obviously occurred with the increase of aging time. In a word, it is believed that investigating the fundamental thermal‐oxidative aging of PA10T/GF composites would be beneficial to optimize and control the service life and applications of materials. POLYM. ENG. SCI., 59:643–656, 2019. © 2018 Society of Plastics Engineers     

Crystallization and thermomechanical properties of PLA composites: Effects of additive types and heat treatment

This research work has concerned a study on thermomechanical and crystallization properties of poly(lactic acid) (PLA) composites containing three different types of additives; namely: kenaf fiber (20 pph), Cloisite30B nanoclay (5 pph), and hexagonal boron nitrile (h‐BN; 5 pph). The composites were prepared using a twin screw extruder before molding. Crystallization behaviors of the various composites were also examined using a differential scanning calorimetry. By adding the additives, tensile modulus of the polymer composites increased, whereas their tensile strength and elongation values decreased as compared to those of the neat PLA. Heat distortion temperature (HDT) values of the materials slightly increased, for about 3–5°C. However, after annealing at 100°C, HDT values of the fabricated PLA composites rapidly increased with annealing time before reaching a plateau after 10 min. The HDT values of above 120°C were achieved when 20 pph kenaf fiber was used as an additive. The above results were in a good agreement with DSC thermograms of the composites, indicating that percentage crystallinity of the materials increased on annealing and crystallization rate of the PLA/kenaf system was the highest. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polypropylene–wood fiber composites: Effect of treatment and mixing conditions on mechanical properties

Polypropylene/wood fiber composites were prepared at three different temperatures: 170°C, 180°C, and 190°C. The surface of wood fibers was modified through the use of silane coupling agents and/or coating with polypropylene or maleated polypropylene. The fiber coating was performed by propylene polymerization in the presence of wood fibers or by immersion in an o-dichlorobenzene polypropylene (or maleated polypropylene) solution. Tensile and three-point bending tests were performed in order to evaluate the adhesion between matrix and wood fibers. Evidence shows that 180°C is the best mixing temperature, while the use of vinyl-tris (2-methoxy ethoxy) silane with or without maleated polypropylene coating is the best surface treatment. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1227–1235, 1997     

High residual mechanical properties at elevated temperatures of bamboo/glass reinforced‐polybenzoxazine hybrid composite

We successfully added bamboo and glass fibers into bisphenol A‐aniline based benzoxazine (BA‐a) resin by hot‐pressing method. In order to improve the interfacial adhesion between bamboo fibers and the matrix, bamboo fibers were pretreated in 6 wt% NaOH solutions for 12 h. The results showed alkali‐treatment had a positive effect on mechanical properties of the composites at both room and elevated temperatures (60°C, 110°C, 160°C, and 210°C). Due to the incorporation of glass fibers, the bamboo/glass reinforced‐polybenzoxazine hybrid composites exhibited highest strength and modulus among all samples and had high residual mechanical properties at elevated temperatures (residual mechanical properties refers to the ratio of strength and modulus of the composites at elevated temperatures to that measured at room temperature). The fractured surface morphologies of the composites were observed by scanning electron microscope. The results showed with the increase of temperature, the debonding and fiber pull‐out became apparent, and the matrix softening could be clearly observed at 210°C. In addition, thermal and thermomechanical properties of neat benzoxazine and the composites were also investigated through thermogravimetric analysis and dynamic mechanical analyzer, respectively. POLYM. ENG. SCI., 59:1818–1829, 2019. © 2019 Society of Plastics Engineers     

Temperature effect on graphene‐filled interface between glass–carbon hybrid fibers and epoxy resin characterized by fiber‐bundle pull‐out test

The overall mechanical performance of glass–carbon hybrid fibers reinforced epoxy composites depends heavily upon fiber–matrix interfacial properties and the service temperatures. Fiber‐bundle pull‐out tests of glass (GF) and/or carbon fiber (CF) reinforced epoxy composites were carried out at room and elevated temperatures. Graphene nanoplatelets were added in the interfacial region to investigate their influence on the interfacial shear strength (IFSS). Results show that IFSS of specimens with fiber‐bundle number ratio of GF:CF = 1:2 is the largest among the hybrid composites, and a positive hybridization effect is found at elevated temperatures. IFSS of all the specimens decreases with the increasing of test temperatures, while the toughness shows a contrary tendency. As verified by scanning electron microscopy observations, graphene nanoplatelets on fiber surface could enhance the IFSS of pure glass/carbon and hybrid fibers reinforced epoxy composites at higher temperatures significantly. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46263.     

Investigations on weld joining of sisal CSM‐thermoplastic composites

An experimental study was conducted to investigate joint efficiency of both, butt, and lap joints of sisal CSM reinforced polymer composites. The thermoplastics, HDPE, and polypropylene (PP) were used separately as matrices in composites. Sisal‐HDPE composites exhibited excellent improvement in tensile strength that reached up to 47.5 MPa at 30 phr loading of sisal CSM as compared with 17.7 MPa of HDPE. Significant improvement in HDT was also observed that increased from 60.2 to 75°C on 0 to 30 phr reinforcement of sisal CSM in HDPE. Similar improvement was noticed with PP where in HDT improved from 69 to 87.6°C on incorporation of 0 to 30 phr sisal CSM. Hot tool welding process was employed for joining the composite materials. The joint efficiency of butt joint of HDPE was observed as 30%. It varied from 48 to 59% for lap joints of different sizes. The joint efficiencies of 20 mm lap joints of different compositions were observed as 59, 98, 75, and 58% in 0, 10, 20, and 30 phr Sisal CSM‐HDPE composites, respectively. Welded joint strengthening is attributed to partial reinforcement of interface that occurs during softening of matrix material which allowed spring back of originally pressed fibers followed by their repositioning in the welded part. POLYM. COMPOS., 36:214–220, 2015. © 2014 Society of Plastics Engineers     

Recycled‐disposable‐chopstick‐fiber‐reinforced polypropylene green composites

The utilization of disposable chopsticks is very popular in Taiwan, China, and Japan and is one of the major sources of waste in these countries. In this study, recycled disposable chopstick fiber was chemically modified. Subsequently, this modified fiber and polypropylene‐graft‐maleic anhydride were added to polypropylene (PP) to form novel fiber‐reinforced green composites. A heat‐deflection temperature (HDT) test showed an increase of approximately 81% for PP with the addition of 60‐phr fibers, and the HDT of the composite could reach up to 144.8°C. In addition, the tensile strength, Young's modulus, and impact strength were 66, 160.3, and 97.1%, respectively, when the composite material was 40‐phr fibers. Furthermore, this type of reinforced PP would be more environmentally friendly than an artificial‐additive‐reinforced one. It could also effectively reduce and reuse the waste of disposable chopsticks and lower the costs of the materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012