The effect of hybridization on mechanical properties of woven kenaf fiber reinforced polyoxymethylene composite

The challenges of using natural fibers in polymer composites include high moisture uptake and poor interfacial bonding with thermoplastic matrix. In this study, the effect of hybridization was investigated to address the challenges of high moisture uptake and balanced mechanical properties in natural fiber reinforced polymer composites. Polyethylene terephthalate fiber (PET) was used in woven kenaf reinforced POM due to its hydrophobic characteristics. The results of tensile test showed that the tensile strength of the interwoven POM/kenaf/PET hybrid composite when tested along kenaf fiber direction, increased from 72 to 85 MPa due to increase in fiber content. Similarly, the tensile strength of the interwoven POM/kenaf/PET hybrid composite increased from 67 to 75 MPa. However, the flexural strength of the interwoven POM/kenaf/PET hybrid composite dropped from 160.1 to 104.9 MPa while that of woven POM/kenaf composite dropped from 191.4 to 90.3 MPa. The interwoven hybrid composite also showed significant improvement in impact strength compared to the woven POM/kenaf composite. The water absorption of the woven POM/kenaf composite dropped by approximately 30% due to hybridization with PET fiber. The results confirmed that hybridization with PET fiber significantly improved the tensile and impact properties of the woven composite and increased its resistance to moisture uptake. POLYM. COMPOS., 35:1900–1910, 2014. © 2014 Society of Plastics Engineers     

Physical and mechanical properties of kenaf/flax hybrid composites

This research investigates the physical and mechanical properties of hybrid composites made of epoxy reinforced by kenaf and flax natural fibers to investigate the hybridization influences of the composites. Pure and hybrid composites were fabricated using bi-directional kenaf and flax fabrics at different stacking sequences utilizing the vacuum-assisted resin infusion method. The pure and hybrid composites' physical properties, such as density, fiber volume fraction (FVF), water absorption capacity, and dimensional stability, were measured. The tests of tensile, flexural, interlaminar shear and fracture toughness (Mode II) were examined to determine the mechanical properties. The results revealed that density remained unchanged for the hybrid compared to pure kenaf/epoxy composites. The tensile, flexural, and interlaminar shear performance of flax/epoxy composite is improved by an increment of kenaf FVF in hybrid composites. The stacking sequence significantly affected the mechanical properties of hybrid composites. The highest tensile strength (59.8 MPa) was obtained for FK2 (alternative sequence of flax and kenaf fibers). However, FK3 (flax fiber located on the outer surfaces) had the highest interlaminar shear strength (12.5 MPa) and fracture toughness (3302.3 J/m²) among all tested hybrid composites. The highest water resistance was achieved for FK5 with the lowest thickness swelling.     

Mechanical properties of natural fiber hybrid composites based on renewable thermoset resins derived from soybean oil,for use in technical applications

Natural fiber composites are known to have lower mechanical properties than glass or carbon fiber reinforced composites. The hybrid natural fiber composites prepared in this study have relatively good mechanical properties. Different combinations of woven and non‐woven flax fibers were used. The stacking sequence of the fibers was in different orientations, such as 0°, +45°, and 90°. The composites manufactured had good mechanical properties. A tensile strength of about 119 MPa and Young's modulus of about 14 GPa was achieved, with flexural strength and modulus of about 201 MPa and 24 GPa, respectively. For the purposes of comparison, composites were made with a combination of woven fabrics and glass fibers. One ply of a glass fiber mat was sandwiched in the mid‐plane and this increased the tensile strength considerably to 168 MPa. Dynamic mechanical analysis was performed in order to determine the storage and loss modulus and the glass transition temperature of the composites. Microstructural analysis was done with scanning electron microscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The Properties of Woven Kenaf and Betel Palm (Areca catechu) Reinforced Unsaturated Polyester Composites

The use of woven betel palm and kenaf lignocellulosic fibers as a reinforcing phase in unsaturated polyester was reported. The morphology, physical properties, and mechanical properties of the natural fibers and resulting woven composites were evaluated. Kenaf fibers exhibit higher tensile properties than betel palm fibers due to the higher amount of cellulose content. From the morphology observation, it is found that the alkaline treatment of the fibers effectively clean the fiber surface and increase the fiber surface roughness. Comparison between treated and untreated woven betel palm and kenaf composites at 7 vol% of fiber content was carried out. Interestingly, untreated woven kenaf composites exhibit comparable flexural strength with those of untreated woven betel palm composites. However, untreated kenaf composites exhibit superior flexural modulus to those of betel palm composites. In general, mechanical properties of the woven composites made from alkali-treated fibers were superior to the untreated fibers.     

Tensile,flexural and impact properties of jute fibre-based thermosetting composites

Abstract

The present study reports static and impact mechanical properties of jute fibre-based thermosetting composites using woven and flat braided jute fabrics. Tensile, three-point flexural and low-to-medium energy drop-weight impact tests were conducted and mechanical properties were evaluated to study their dependence upon surface modifications of the fibre materials due to bleaching and coating treatments. Full-bleaching (longer and rigorous) treatments improved interfacial bonding and tensile strength properties of the woven jute composites compared to unbleached and half-bleached counterparts. Bleaching treatments did not seem to improve the flexural strength of composites. Unbleached (natural) jute composites have relatively better flexural strength due to reduced microstructural waviness or fibre crimping to facilitate flexural failure. With coated jute yarns, the tensile properties of the resultant flat braided composites slightly degraded, whereas the flexural properties showed clear improvements. The changes in the mechanical properties were broadly related to the accompanying modifications and to the state of microstructural imperfections, namely fibre/matrix interfacial adhesion, severity of resin matrix shrinkage during the curing process, fibre/matrix debonding and distribution of disbonds within the matrix region, and also to the relative fibre filament density along the loading axis, in the cured composite structure. There was a clear indication that natural woven jute composites could be more effective in applications requiring better impact damage resistance, energy absorption capability and improved progressive crushing behaviour.     

Mechanical properties of carbon woven reinforced epoxy matrix composites. A study on the influence of matrix modification with polysulfone

An experimental investigation has been carried out to study the influence of thermoplastic addition on the mechanical properties of woven carbon fiber/epoxy matrix composites. As toughening agent bisphenol‐A polysulfone, PSu, has been added to the epoxy matrix. Flexural tests haved been performed to characterize the mechanical behavior of unmodified and PSu‐modified bulk tetra‐ and bifunctional epoxy matrices and also for the corresponding woven carbon fiber, CF, composite materials. Three‐point notched flexural tests been used to investigate the influence of polysulfone addition in the mode‐I fracture properties of the bulk epoxy matrices, relating them to their microstructural features investigated by atomic force microscopy (AFM). The double‐cantilever bea (DCB) and the end‐notched flexural (ENF) tests have been applied to characterize the interlaminar fracture toughness of the corresponding composites. For composites, the flexural properties were simmilar independent of the funcetionality of the epoxy matrix and of the thermoplastic content. Nevertheless, PSu addition to the epoxy matrix celarly enhanced the ode‐I and II interlaminar fracture toughness of the corresponding composites, the immprovement being higher for the composites manufactured with the bifunctional epoxy matrix at every thermoplastic content because of the lower crosslink density of the epoxy matrix.     

Replacement of styrene with acrylated epoxidized soybean oil in an unsaturated polyester resin from propylene glycol,isophthalic acid,and maleic anhydride

Commercial unsaturated polyester (UPE) resins typically contain a high amount of volatile toxic styrene. A non‐volatile acrylated epoxidized soybean oil (AESO) was found to be an excellent replacement of styrene in a commercially available UPE resin [designated as Styrene‐(PG‐IPA‐MA)] that is derived from propylene glycol (PG), isophthalic acid (IPA), and maleic anhydride (MA) in terms of the mechanical properties of the resulting kenaf fiber‐reinforced composites. The AESO‐(PG‐IPA‐MA) resins had low viscosity and long pot life below 70°C for a typical fiber‐reinforced composite application. AESO and PG‐IPA‐MA were not able to form a strong polymer matrix individually for fiber‐reinforced composites. However, a combination of AESO and PG‐IPA‐MA saw strong synergistic effects between them. The flexural, tensile, and water absorption properties of kenaf fiber‐reinforced composites made from AESO‐(PG‐IPA‐MA) resins were comparable with or even superior to those from the Styrene‐(PG‐IPA‐MA) resin. The AESO/(PG‐IPA‐MA) weight ratio was investigated for maximizing the mechanical properties of the kenaf fiber‐reinforced composites. The curing mechanism of the AESO‐(PG‐IPA‐MA) resins is discussed in detail. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43052.     

Effect of coir fiber loading on mechanical and morphological properties of oil palm fibers reinforced polypropylene composites

Hybrid composites were fabricated by compounding process with varying the relative weight fraction of oil palm empty fruit bunch (EFB) and coir fibers to assess the effect of hybridization of oil palm EFB with coir fibers in polypropylene (PP) matrix. The mechanical and morphological properties of oil palm/coir hybrid composites were carried out. Tensile and flexural properties of oil EFB‐PP composites enhanced with hybridization of coir fibers except coir/oil palm EFB (25:75) hybrid composite, whereas highest impact properties at oil palm:coir fibers with 50:50 ratios. Results shown that hybrid composites with oil palm:coir fibers with 50:50 ratios display optimum mechanical properties. In this study, scanning electron microscopy (SEM) had been used to study morphology of tensile fractured surface of hybrid composites. Its clear from SEM micrograph that coir/EFB (50:50) hybrid composites display better tensile properties due to strong fiber/matrix bonding as compared with other formulations which lead to even and effective distribution of stress among fibers. The combination of oil palm EFB/coir fibers with PP matrix produced hybrid biocomposites material can be used to produce components such as rear mirrors' holder and window levers, fan blades, mallet, or gavel. POLYM. COMPOS., 35:1418–1425, 2014. © 2013 Society of Plastics Engineers     

The effects of alkali treatment on the mechanical and morphological properties of Pennisetum purpureum/glass-reinforced epoxy hybrid composites

The effects of alkali treatment on the mechanical properties, void contents and morphological of Pennisetum purpureum/glass-reinforced epoxy hybrid composites were studied. The composites were produced using the vacuum infusion method. Pennisetum purpureum fibres were treated with 5 and 10% dilute sodium hydroxide (NaOH) solution for 6?h. The epoxy resin was mixed with either the treated or untreated Pennisetum purpureum/glass fibres to a ratio of 70:30 (by volume). Tensile and flexural tests were performed on the composites in accordance with ASTM D638 and ASTM D790, respectively. The hybrid composites that contained 5% NaOH-treated Pennisetum purpureum fibres exhibited the greatest tensile and flexural strengths with lower void contents. Field-emission scanning electron microscopy fractography supported the findings showing lesser voids and fibre pull-outs suggesting good interfacial bonding between the matrix and reinforcement. The reduced of the void contents is suspected due to the reduced hemicellulose content within the treated Pennisetum purpureum fibre.     

Microstructure and fracture behavior of (co)injection‐molded polyamide 6 composites with short glass/carbon fiber hybrid reinforcement

The mechanical and fracture properties of injection molded short glass fiber)/short carbon fiber reinforced polyamide 6 (PA 6) hybrid composites were studied. The short fiber composites of PA 6 glass fiber, carbon fiber, and the hybrid blend were injection molded using a conventional machine whereas the two types of sandwich skin–core hybrids were coinjection molded. The fiber volume fraction for all formulations was fixed at 0.07. The overall composite density, volume, and weight fraction for each formulation was calculated after composite pyrolysis in a furnace at 600°C under nitrogen atmosphere. The tensile, flexural, and single‐edge notch‐bending tests were performed on all formulations. Microstructural characterizations involved the determination of thermal properties, skin–core thickness, and fiber length distributions. The carbon fiber/PA 6 (CF/PA 6) formulation exhibits the highest values for most tests. The sandwich skin‐core hybrid composites exhibit values lower than the CF/PA 6 and hybrid composite blends for the mechanical and fracture tests. The behaviors of all composite formulations are explained in terms of mechanical and fracture properties and its proportion to the composite strength, fiber orientation, interfacial bonding between fibers and matrix, nucleating ability of carbon fibers, and the effects of the skin and core structures. Failure mechanisms of both the matrix and the composites, assessed by fractographic studies in a scanning electron microscope, are discussed. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 957–967, 2005     

Non‐traditional lightweight polypropylene composites reinforced with milkweed floss

Lightweight composites are preferred for automotive applications due to the weight restrictions and also due to the presence of inherent voids that can enhance the sound absorption of these composites. The density of the reinforcing materials plays a crucial role in such lightweight composites. Milkweed is a unique natural cellulose fiber that has a completely hollow center and low density (0.9 g cm^?3) unlike any other natural cellulose fiber. The low density of milkweed fibers will allow the incorporation of higher amounts of fiber per unit weight of a composite, which is expected to lead to lightweight composites with better properties. Polypropylene (PP) composites reinforced with milkweed fibers have much better flexural and tensile properties than similar PP composites reinforced with kenaf fibers. Milkweed fiber‐reinforced composites have much higher strength but are stiffer than kenaf fiber‐reinforced PP composites. Increasing the proportion of milkweed in the composites from 35 to 50% increases the flexural strength but decreases the tensile strength. The low density of milkweed fibers allows the incorporation of higher amounts of fibers per unit weight of the composites and hence provides better properties compared to composites reinforced with common cellulose fibers with relatively high density. This research shows that low‐density reinforcing materials can more efficiently reinforce lightweight composites. Copyright © 2010 Society of Chemical Industry     

Effects of in-situ carbon layer and volume fraction of SiC fiber on the mechanical properties and fracture behaviors of SiCf/SiC composites fabricated by a modified PIP method

Unidirectional SiC_f/SiC composites (UD SiC_f/SiC composites) with excellent mechanical properties were successfully fabricated by a modified PIP method which involved the preparation of film-like matrix containing carbon layer with a low concentration PCS solution followed by the rapid densification of composites with a high concentration PCS solution. Carbon layers were in-situ formed and alternating with SiC layers in the as-received matrix. The unique microstructure endows the composites with appropriate interfacial bonding state, good load transfer ability of interphase and matrix and load bearing ability of fiber, and great crack deflection capacity, which ensures the synergy of high strength and toughness of composites. It is also found that the fiber volume fraction in the preform makes a non-negligible effect on the distribution of interphase and matrix, of which the reasonable adjustment can be utilized to optimize the mechanical properties of composites. Compared with the composites only using high concentration PCS solution, the UD SiC_f/SiC composites prepared by the modified PIP method exhibit superior mechanical properties. Ultrahigh flexural strength of 1318.5 ± 158.3 MPa and fracture toughness of 47.6 ± 5.6 MPa·m^1/2 were achieved at the fiber volume fraction of 30%.     

Natural fiber blend—nylon 6 composites

In this study, engineering thermoplastic composites were prepared from natural fiber blend–filled nylon 6. Natural fiber blend from a mixture of kenaf, flax, and hemp fibers were added to nylon 6 using melt mixing to produce compounded pellets. The natural fibers/ nylon6 composites with varying concentrations of natural fibers (from 5 to 20 wt%) were prepared by injection molding. The tensile and flexural properties of the nylon 6 composites were increased significantly with the addition of the natural fiber blend. The maximum strength and modulus of elasticity for the nylon 6 composites were achieved at a natural fiber blend weight fraction of 20%. The Izod impact strength of composites decreased with the incorporation of natural fibers without any surface treatments and coupling agent. The melt flow index (MFI) also decreased with increasing natural fiber blend loading. The results of tensile and flexural modulus of elasticity (FMOE) are in accordance with the rheological data from the MFI measurements. The increase in the tensile and flexural properties indicated that efficient bonding occurred between the natural fibers and nylon 6. No fiber pullout was observed during the scanning electron microscopic analysis of the fracture surfaces. The higher mechanical results with lower density demonstrate that a natural fiber blend can be used as a sufficient reinforcing material for low‐cost, eco‐friendly composites in the automotive industry and in other applications such as the building and construction industries, packaging, consumer products, etc.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Hybridization effect of basalt and carbon fibers on impact and flexural properties of phenolic composites

In this study, the impact and flexural properties of woven basalt fiber/phenolic (BFP), woven carbon fiber/phenolic (CFP) and woven basalt/woven carbon hybrid phenolic (BCFP) composites are investigated. The hybridization effect of woven basalt and woven carbon fibers on the impact energy absorption and flexural properties is investigated for various weight ratios of basalt/carbon hybrid fibers such as 1:0, 0.83:0.17, 0.68:0.32, 0.61:0.39, 0.34:0.66 and 0:1. It is found that the impact properties of the composites are strongly improved when the basalt fiber increased. Impact energy absorption of CFP composite showed a regular trend of increase with increasing weight ratio of basalt fiber in hybrid fiber composite. The lowest impact energy absorption values are found for the composites with weight ratio 0:1 (CFP), with average of 70 kJ/m². Corresponding values for energy absorptions are obtained for 0.83:0.17, 0.68:0.32, 0.61:0.39, 0.34:0.66 basalt/carbon weight ratio in hybrid composites. The impact energy absorption of hybrid composites (BCFP) shows the highest value with an average of 219 kJ/m², when the weight ratio of 0.83:0.17 is used. Finally, the impact energy absorption of BFP composites with the weight ratio of 1:0 shows the highest value of 268 kJ/m². The experimental evidence shows that the hybrid composites based on combinations of stiff carbon fibers and tough basalt fibers have good flexural properties and therefore, they can be used as promising materials in a number of engineering sectors such as the protective structures.     

A study of the mechanical properties of randomly oriented short banana and sisal hybrid fiber reinforced polyester composites

The mechanical performance of short randomly oriented banana and sisal hybrid fiber reinforced polyester composites was investigated with reference to the relative volume fraction of the two fibers at a constant total fiber loading of 0.40 volume fraction (V_f), keeping banana as the skin material and sisal as the core material. A positive hybrid effect is observed in the flexural strength and flexural modulus of the hybrid composites. The tensile strength of the composites showed a positive hybrid effect when the relative volume fraction of the two fibers was varied, and maximum tensile strength was found to be in the hybrid composite having a ratio of banana and sisal 4 : 1. The impact strength of the composites was increased with increasing volume fraction of sisal. However, a negative hybrid effect is observed when the impact strength of the composites is considered. Keeping the relative volume fraction of the two fibers constant, that is, banana : sisal = 0.32 : 0.08 (i.e., 4 : 1), the fiber loading was optimized and different layering patterns were investigated. The impact strength of the composites was increased with fiber loading. Tensile and flexural properties were found to be better at 0.40 V_f. In the case of different layering patterns, the highest flexural strength was observed for the bilayer composites. Compared to other composites, the tensile properties were slightly higher for the composite having banana as the skin material and sisal as the core material. Scanning electron micrographs of the tensile and impact fracture surfaces of the hybrid composites having volume fraction 0.20 and 0.40 V_f were studied. The experimental tensile strength and tensile modulus of hybrid composites were compared with those of theoretical predictions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1699–1709, 2005     

Effect of stacking sequence on mechanical properties of hybrid flax/jute fibers reinforced thermoplastic composites

In this study, the hybrid composites were prepared by stacking jute/PP nonwoven and flax/MAPP woven fabrics in defined sequences. Polypropylene (PP) and maleic anhydride grafted polypropylene (MAPP) were used as matrix materials. Jute and flax fibers were treated with alkali solution in order to improve the interface properties of the resultant composites. The mechanical properties of these hybrid composites were analyzed by means of tensile, flexural, and drop‐weight impact tests. The effect of fabric stacking sequence on the mechanical properties of the composites was investigated. The stacking of nonwovens at the top and in alternate layers has resulted in maximum flexural strength, flexural stiffness, and impact force. It was also shown that hybrid composites have improved tensile, flexural, and impact properties in comparison to neat PP matrix. POLYM. COMPOS., 36:2167–2173, 2015. © 2014 Society of Plastics Engineers     

Ionomer. I. The effect of woven glass mat reinforcement on tensile properties

An investigation was conducted on ionomer polymer. The ionomer pellets were molded into a thin sheet before fabrication into composites. The reinforcing agent used was woven glass mat. Before fabrication, the woven glass mat was treated with the following: 1. silane coupling agent for 5 min and dried at room temperature; 2. silane coupling agent for 5 min and dried in the oven at 110°C for 15 min; 3. Ultraviolet radiation for 5 min; and 4. silane (oven dried + ultraviolet). The composites were fabricated at various pressure, time, and temperature. An ideal processing condition was established, i.e., pressure = 5 MPa, temperature = 180°C, and the impregnation time = 30 min. The void contents of the composites were estimated using the ignition method and the tensile properties were measured. The results revealed that good impregnation of the matrix ionomer into the reinforcing agent can be achieved at 180°C. This was confirmed by low void content as compared with other test temperatures. Further clarification was through the tensile properties, which were higher than those at lower temperatures (120 and 150°C). The effect of fiber orientation was checked, and both 0 and 90° had identical strengths and moduli irrespective of the various fiber treatments. Apart from the void contents, the degree of impregnation was also checked based on the tensile strengths in 45, 25, and 60° fiber orientations. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1395–1400, 2001     

Ultra-Violet Radiation-Cured Biofiber Composites from Kenaf: The Effect of Montmorillonite on the Flexural and Impact Properties

Abstract

Biofiber composites, cured by ultra-violet (UV) radiation were produced using kenaf fibers as the reinforcing agent and unsaturated polyester as the matrix. This research work focused on the effects of the incorporation of kenaf fiber, montmorillonite (MMT), and cetyl trimethyl ammonium bromide-modified MMT (CTAB-MMT) in the unsaturated polyester composite. Overall, the incorporation of kenaf fibers in the form of mat had improved the flexural and impact properties of the composites. Addition of MMT into the kenaf fiber-polyester system showed an improvement up to 1% MMT after which it decreased. The increase was attributed to better stress transfer mechanism in the matrix. However, further increase in the MMT loading had resulted in the decrease in the properties, which was believed to be due to agglomeration. Modification of MMT with CTAB had produced composites with higher flexural and impact properties as compared to those without modification. This was attributed to a combination of effective dispersion of MMT in the matrix, availability of effective high aspect ratio MMT, and enhanced compatibility between CTAB-MMT with the matrix.     

Pultruded fiber-reinforced poly(methyl methacrylate) composites. II. Static and dynamic mechanical properties,environmental effect,and postformability

This paper presents a novel process developed to manufacture poly(methyl methacrylate) (PMMA) pultruded composite. The mechanical, thermal, and dynamic mechanical properties, environmental effect, postformability of various fiber (glass, carbon, and Kevlar 49 aramid fiber) reinforced pultruded PMMA composites have been studied. Results show mechanical properties (i.e., tensile strength, specific tensile strength, tensile modulus, and specific flexural strength) and thermal properties (HDT) increase with fiber content. Kevlar fiber/PMMA composites possess the highest specific tensile strength and HDT, carbon fiber/PMMA composites show the highest tensile strength and tensile modulus, and glass fiber/PMMA composites show the highest specific flexural strength. Pultruded glass-fiber-reinforced PMMA composites exhibit good weather resistance. These composite materials can be postformed by thermoforming under pressure, and mechanical properties of postformed products can be improved. The dynamic shear storage and loss modulus (G′, G″) of pultruded glass-fiber-reinforced PMMA composites increased with decreasing pulling rate, and their shear storage moduli are higher than those of pultruded Nylon 6 and polyester composites.     

The effect of ambient moisture and temperature conditions on the mechanical properties of glass fiber/carbon fiber/nylon 6 sandwich hybrid composites consisting of skin‐core morphologies

The concept of skin‐core (SC) morphology was used to make sandwich hybrid composites in which the skin and core were composed of different fibers in the same matrix. The sandwich blends comprising glass skin with carbon core and vice versa were compared with those of the hybrid composite, while the respective carbon (CF) and glass fiber (GF) composites served as points of reference. The composites were compounded and fabricated into injection molded tensile specimens and 3‐mm thick plaques. The effect of ambient temperature and moisture was studied. The fracture mechanical characterization of the various materials was done by using notched compact tension (CT) specimens. Tensile properties were also used to characterize the composites. Morphogical studies based on scanning electron microscopy and light microscopy were used to elucidate fracture characteristics. Deterioration of properties was noticed under hot and humid conditions. Synergism in flexural properties was observed in the CF/GF/PA hybrid composite. The mechanical properties of the CF/GF/PA hybrid are closer to those of CF/PA, suggesting a cost advantage by substituting half of the carbon fibers with glass fibers. Dynamic mechanical analysis results revealed that synergism in T_g is attained by blending or sandwiching glass and carbon fibers. Morphological studies reaffirmed the skin‐core morphology of the composites. POLYM. COMPOS., 26:52–59, 2005. © 2004 Society of Plastics Engineers.