Interphase characterization and modeling of tensile modulus in epoxy/silica nanocomposites

The incorporation of second dispersed particulate phases in a polymer matrix enhances its mechanical properties. Because of the high surface to volume ratio of nanoparticles, the molecular structure of the matrix is altered at the nanoparticle/matrix interface and the volume of this perturbed region could be significant. These improved properties are produced by the interfacial interaction of the nanometric domains. In this research, epoxy matrix modified with three different sizes of nanosilica (12, 20, and 40 nm) and the effect of the interphase characteristics on the tensile properties of nanocomposites was investigated. At first, the theoretical values of the elastic modulus using a two-phase mathematical model compared with the experimental data obtained from the nanocomposite samples and values between 8 and 10 nm were estimated for the interphase thickness. Afterward, considering the three-phase model, it takes into account that three different regions for interphase volume fraction, including single particles, polymer trapping, and agglomerated nanoparticles, and an equation for evaluation of interphase volume fraction are defined. Also, the interphase tensile modulus was considered continuously changing from the properties of nanoparticle to the polymer matrix properties. Finally, the overall tensile modulus of nanocomposites, which considers different key parameters including nanoparticle size, values for the interphase thickness (h), and interphase tensile modulus (E_i), were calculated. The results were compared with the experimental ones of other studies and a good agreement was found. The smallest value of h as 6 nm for samples containing 12-nm diameter nanosilica and highest value of h as 8 nm for samples containing 40-nm diameter nanosilica is reported.     

Synthesis and characterization of organic/inorganic epoxy nanocomposites from poly(aminopropyl/phenyl)silsesquioxanes

Organic/inorganic epoxy nanocomposites containing diglycidyl ether of bisphenol A (DGEBA), 4‐methylhexahydrophthalic anhydride (MHHPA) and poly(aminopropyl/phenyl) silsesquioxanes (PAPPS) were prepared and characterized. PAPPS were synthesized via fluoride‐catalyzed cage formation from random‐structured poly(phenyl)silsesquioxane (PPS) and 3‐aminopropyltriethoxysilane (APTES) in tetrahydrofuran (THF) using tetrabutylammonium fluoride (TBAF) catalyst containing substantial water. The PPS/APTES stoichiometric ratios were varied. The FTIR, ¹H, solid‐state 29 Si‐NMR studies show that PAPPS probably consists of cages, partial cages, and some linear structures containing phenyl and aminopropyl functional groups. The amine content was determined by back titration and elemental analysis. In comparison with neat epoxy, incorporation of these materials can improve the resultant thermal stabilities, raise glass transition temperatures (T_gs), and reduce coefficients of thermal expansion (CTEs) of epoxy nanocomposites as confirmed by TG/DTA, DMA and TMA tests, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Response surface predictions of the viscoelastic properties of vapor‐grown carbon nanofiber/vinyl ester nanocomposites

A full factorial design of experiments and response surface methodology were used to investigate the effects of formulation, processing, and operating temperature on the viscoelastic properties of vapor‐grown carbon nanofiber (VGCNF)/vinyl ester (VE) nanocomposites. Factors included VGCNF type (pristine, oxidized), use of a dispersing agent (DA) (no, yes), mixing method (ultrasonication, high‐shear mixing, and a combination of both), VGCNF weight fraction (0.00, 0.25, 0.50, 0.75, and 1.00 parts per hundred parts resin (phr)), and temperature (30, 60, 90, and 120°C). Response surface models (RSMs) for predicting storage and loss moduli were developed, which explicitly account for the effect of complex interactions between nanocomposite design factors and operating temperature on resultant composite properties; such influences would be impossible to assess using traditional single‐factor experiments. Nanocomposite storage moduli were maximized over the entire temperature range (～20% increase over neat VE) by using high‐shear mixing and oxidized VGCNFs with DA or equivalently by employing pristine VGCNFs without DA at ～0.40 phr of VGCNFs. Ultrasonication yielded the highest loss modulus at ～0.25 phr of VGCNFs. The RSMs developed in this investigation may be used to design VGCNF‐enhanced VE matrices with optimal storage and loss moduli for automotive structural applications. Moreover, a similar approach may be used to tailor the mechanical, thermal, and electrical properties of nanomaterials over a range of anticipated operating environments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Layer‐by‐layer fabrication of nacre inspired epoxy/MMT multilayered composites

The organic–inorganic hybrid multilayered composites are prepared using a unique combination of poly[(o‐cresyl glycidyl ether)‐co‐formaldehyde] (CNER), amino modified montmorillonite (NH₂‐MMT), and polyethyleneimine (PEI). This tricomponent composite multilayer PEI(CNER/NH₂‐MMT/PEI)_n deposited via layer ‐ by ‐ layer technique is based upon synergistic combination of covalent and hydrogen bonding. The growth of multilayer was monitored using UV–vis spectroscopy and ellipsometry. When subjected to optical analyses, the prepared multilayered composite films revealed profound optical transmittance ～83%–87%. The surface morphological analysis by atomic force microscopy and scanning electron microscopy revealed uniform arrangement of organic–inorganic components with relative increase in intensity of elements (C, N, O, Si) as confirmed by X‐ray photoelectron spectroscopy studies. The multilayered composites possess 1.99 GPa hardness making them potential candidate for a number of applications where mechanical strength is desired. Moreover, significant resistance against alkaline and organic solvents at minimal deterioration of circa 0.12% has also been observed for the prepared films. The epoxy clay based thin films being robust, scratch resistant, hydrophilic, chemically inert, and mechanically strong are potential candidates for advanced environmental applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46079.     

Preparation and characterization of epoxy nanocomposites containing surface‐modified graphene oxide

A three‐step grafting procedure has been used to graft the epoxy monomers (DER332) and the curing agents (diamino diphenyl methane (DDM), onto graphene oxide (GO) surface. The surface modification of GO has been performed by grafting of Jeffamine D‐2000, followed with subsequent grafting of DER332 and DDM, respectively. Fourier transform spectroscopy and thermogravimetric analysis indicate successful surface modification. The resulting modified GO, that is, (DED)‐GO, can be well dispersed in the epoxy monomers. The epoxy nanocomposites containing different GO contents can then be prepared through curing processes. The dispersion of GO in the nanocomposites is characterized by transmission electron microscopy. It is found that the tensile strength and elongation at break of epoxy nanocomposite with only 0.2 wt % DED‐GO are increased by 30 and 16% as compared with the neat epoxy resin, respectively. Dynamic mechanical analysis results show that 62% increase in storage modulus and 26°C enhancement in the glass transition temperature of the nanocomposite have been achieved with the incorporation of only 0.2 wt % of DED‐GO into the epoxy. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40236.     

Effects of facile amine‐functionalization on the physical properties of epoxy/graphene nanoplatelets nanocomposites

Graphene nanoplatelets (GNPs) have excellent thermal, electrical, and mechanical properties. The incorporation of GNPs into a polymer can remarkably enhance the thermal and mechanical properties of the polymer especially when GNPs are well dispersed in the polymer matrix with strong interfacial bonding. Therefore, in this study, GNPs were amine‐functionalized by covalently bonding 4,4′‐methylene dianiline onto their surfaces via a facile synthetic route. The amine‐functionalization was confirmed by FTIR spectroscopy and TGA. Epoxy/GNPs nanocomposites were prepared and their curing behavior, thermomechanical properties and impact strength were investigated. The amine‐functionalization increased curing rate, storage modulus, thermal dimensional stability, and impact strength of the nanocomposites. The SEM images for the fracture surface of the nanocomposite with amine‐functionalized GNPs showed a smooth and ductile failure‐like surface, resulted from the improved interfacial bonding between GNPs and the epoxy matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42269.     

Characterization,prediction, and optimization of flexural properties of vapor‐grown carbon nanofiber/vinyl ester nanocomposites by response surface modeling

A design of experiments and response surface modeling were performed to investigate the effects of formulation and processing factors on the flexural moduli and strengths of vapor‐grown carbon nanofiber (VGCNF)/vinyl ester (VE) nanocomposites. VGCNF type (pristine, surface‐oxidized), use of a dispersing agent (no, yes), mixing method (ultrasonication, high‐shear mixing, and a combination of both), and VGCNF weight fraction (0.00, 0.25, 0.50, 0.75, and 1.00 parts per hundred parts resin (phr)) were selected as independent factors. Response surface models were developed to predict flexural moduli and strengths as a continuous function of VGCNF weight fraction. The use of surface‐oxidized nanofibers, a dispersing agent, and high‐shear mixing at 0.48 phr of VGCNF led to an average increase of 19% in the predicted flexural modulus over that of the neat VE. High‐shear mixing with 0.60 phr of VGCNF resulted in a remarkable 49% increase in nanocomposite flexural strength relative to that of the neat VE. This article underscores the advantages of statistical design of experiments and response surface modeling in characterizing and optimizing polymer nanocomposites for automotive structural applications. Moreover, response surface models may be used to tailor the mechanical properties of nanocomposites over a range of anticipated operating environments. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2087–2099, 2013     

In situ polymerization of bio‐based thermosetting polyurethane/graphene oxide nanocomposites

Novel bio‐based polyurethane/graphene oxide (GO) nanocomposites have been successfully synthesized from biorenewable epoxidized soybean‐castor oil fatty acid‐based polyols with considerable improvement in mechanical and thermal properties. The GO was synthesized via a modified pressurized oxidation method, and was investigated using Raman spectra, AFM and XPS, respectively. The toughening mechanism of GO in the bio‐based polyurethane matrix was explored. The elongation at break and toughness of polyurethane were increased by 1.3 and 0.8 times with incorporation of 0.4 wt % GO, respectively. However, insignificant changes in both mechanical strength and modulus were observed by adding GO. The results from thermal analysis indicated that the GO acts as new secondary soft segments in the polyurethane which lead to a considerable decrease in the glass transition temperature and crosslink density. The SEM morphology of the fracture surface after tensile testing showed a considerable aggregation of graphene oxide at concentrations above 0.4 wt %. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41751.     

Development of multiwalled‐carbon‐nanotube‐welded carbon fibers and evaluation of the interfacial strength in epoxy composites

Multiwalled carbon nanotube (MWCNT)‐welded carbon fibers (CFs) were prepared by a three‐step process, which included polyacrylonitrile (PAN) coating, MWCNT absorption, and heat treatment. The structure of these materials was characterized by scanning electron microscopy, Fourier‐transform infrared spectroscopy, and Raman spectroscopy. The MWCNTs were uniformly assembled on the surface of the PAN‐coated CFs and welded by a PAN‐based carbon layer after heat treatment. The contact angle of the MWCNT‐welded CFs in the epoxy resins was 41.70°; this was 22.35% smaller than that of the unsized CFs. The interfacial shear strength (IFSS) of the MWCNT‐welded CF–epoxy composite was 83.15 MPa; this was 28.89% higher than that of the unsized CF–epoxy composite. The increase in the IFSS was attributed to the enhancement of adhesions between the CFs and polymer matrix through the welding of the MWCNTs on the CFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45027.     

Synthesis of EP‐POSS mixture and the properties of EP‐POSS/epoxy,SiO2/epoxy,and SiO2/EP‐POSS/epoxy nanocomposite

The hybrid material of EP‐POSS mixture was synthesized by the hydrolysis and condensation of (γ‐glycidoxypropyl) trimethoxysilane. A series of binary systems of EP‐POSS/epoxy blends, epoxy resin modified by silica nanoparticles (SiO₂/epoxy), and ternary system of SiO₂/EP‐POSS/epoxy nanocomposite were prepared. The dispersion of SiO₂ in the matrices was evidenced by transmission electron micrograph, and the mechanical properties, that is, flexural strength, flexural modulus, and impact strength were examined for EP‐POSS/epoxy blends, SiO₂/epoxy, and SiO₂/EP‐POSS/epoxy, respectively. The fractured surface of the impact samples was observed by scanning electron micrograph. Thermogravimetry analysis were applied to investigate the different thermal stabilities of the binary system and ternary system by introducing EP‐POSS and SiO₂ to epoxy resin. The results showed that the impact strength, flexural strength, and modulus of the SiO₂/EP‐POSS/epoxy system increased around by 57.9, 14.1, and 44.0% compared with the pure epoxy resin, T_i, T_max and the residues of the ternary system were 387°C, 426°C, and 25.2%, increased remarkably by 20°C, 11°C and 101.6% in contrast to the pure epoxy resin, which was also higher than the binary systems. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 810‐819, 2013     

Improving thermal conductivity and shear strength of carbon nanotubes/epoxy composites via thiol‐ene click reaction

This study investigates the effect of the thiol‐ene click reaction on thermal conductivity and shear strength of the epoxy composites reinforced by various silane‐functionalized hybrids of sulfhydryl‐grafted multi‐walled carbon nanotubes (SH‐MWCNTs) and vinyl‐grafted MWCNTs (CC‐MWCNTs). The results of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM) show that the sulfhydryl groups and vinyl groups are successfully grafted onto the surface of MWCNTs, after treatment of MWCNT with triethoxyvinylsilane and 3‐mercaptopropyltrimethoxysilane, respectively. Scanning electron microscopy (SEM), HotDisk thermal constant analyzer (HotDisk), optical microscope, and differential scanning calorimetry (DSC) are used to characterize the resultant composites. It is demonstrated that the hybrid of 75 wt % SH‐MWCNTs and 25 wt % CC‐MWCNTs has better dispersion and stability in epoxy matrix, and shows a stronger synergistic effect in improving the thermal conductivity of epoxy composite via the thiol‐ene click reaction with 2,2′‐azobis(2‐methylpropionitrile) as thermal initiator. Furthermore, the tensile shear strength results of MWCNT/epoxy composites and the optical microscopy photographs of shear failure section indicate that the composite with the hybrid MWCNTs has higher shear strength than that with raw MWCNTs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44579.     

In situ polymerization of polyimide‐based nanocomposites via covalent incorporation of functionalized graphene nanosheets for enhancing mechanical,thermal, and electrical properties

In this study, we report an effective method to fabricate high‐performance polyimide (PI)‐based nanocomposites using 3‐aminopropyltriethoxysilane functionalized graphene oxide (APTSi‐GO) as the reinforcing filler. APTSi‐GO nanosheets exhibit good dispersibility and compatibility with the polymer matrix because of the strong interfacial covalent interactions. PI‐based nanocomposites with different loadings of functionalized graphene nanosheets (FGNS) were prepared by in situ polymerization and thermal imidization. The mechanical performance, thermal stability, and electrical conductivity of the FGNS/PI nanocomposites are significantly improved compared with those of pure PI by adding only a small amount of FGNS. For example, a 79% improvement in the tensile strength and a 132% increase in the tensile modulus are achieved by adding 1.5 wt % FGNS. The electrical and thermal conductivities of 1.5 wt % FGNS/PI are 2.6 × 10^?3 S/m and 0.321 W/m·K, respectively, which are ～10¹⁰ and two times higher than those of pure PI. Furthermore, the incorporation of graphene significantly improves the glass‐transition temperature and thermal stability. The success of this approach provides a good rationale for developing multifunctional and high‐performance PI‐based composite materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42724.     

Multifunctional epoxy resin/polyacrylonitrile‐lithium trifluoromethanesulfonate composites films with very high transparency,high dielectric permittivity,breakdown strength and mechanical properties

Multifunctional transparent composite films with high dielectric permittivity (high‐k), breakdown strength, and mechanical properties are urgently required by cutting‐edge fields. Herein, novel multifunctional films were facilely prepared through building unique cross‐linked structure based on epoxy resin (EP) and polyacrylonitrile (PAN)‐lithium trifluoromethane sulfonate (LiTf) complex. Compared with high‐k materials reported previously, EP/(PAN‐LiTf) films simultaneously show very high transparency, good flexibility, high tensile, and breakdown strengths. For 0.22EP/(PAN‐LiTf) film with 22 wt % EP, its average transmittance and elongation at break are as high as 91% (600–800 nm) and 12.7%, respectively; moreover, its dielectric permittivity, AC breakdown strength and the maximum energy density are severally about 4.9, 1.8, and 15.2 times of those of EP resin, completely overcoming the sticky problems in conductor/polymer composites. The origin behind these attractive properties is intensively discussed, and believed to be attributed to the unique structure of EP/(PAN‐LiTf) films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45218.     

Enhanced mechanical and thermal properties of biodegradable poly(butylene succinate‐co‐adipate)/graphene oxide nanocomposites via in situ polymerization

Poly(butylene succinate‐co‐butylene adipate) (PBSA)/graphene oxide (GO) nanocomposites were synthesized via in situ polymerization for the first time. Atomic force microscopy demonstrated the achievement of a single layer of GO, and transmission electron microscopy proved the homogeneous distribution of GO in the PBSA matrix. Fourier transform infrared spectroscopy results showed the successful grafting of PBSA chains onto GO. With the incorporation of 1 wt % GO, the tensile strength and flexural modulus of the PBSA were enhanced by 50 and 27%, respectively. The thermal properties characterized by differential scanning calorimetry and thermogravimetric analysis showed increases in the melting temperatures, crystallization temperatures, and thermal stability. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4075–4080, 2013     

Thermal,mechanical properties,and low‐temperature performance of fibrous nanoclay‐reinforced epoxy asphalt composites and their concretes

Epoxy asphalt (EA) concretes have been widely used in the pavement of orthotropic steel bridge decks. The objective of this study was to figure out the enhanced effects of natural fibrous attapulgite (ATT) as a reinforced nanofiller in ATT/EA nanocomposites through a comparison of the properties of the composites with a series of various nanoclay loadings. The rheological properties, glass transition, thermal stability, mechanical properties, and morphology of the ATT/EA composites were characterized. Furthermore, the low‐temperature flexibility of the ATT/EA concretes was investigated. The test results show that the addition of ATT had no significant effect on the rotational viscosity of EA in the initial stage of the curing reaction. In addition, the ATT/EA composites showed better performance than the neat one in thermal stability with a higher glass‐transformation temperature. The tensile strength and elongation at break of the ATT/EA composites at a loading of 0.5 wt % ATT were 21 and 22% higher than those of the neat EA. The addition of ATTs also enhanced the low‐temperature flexibility of the EA concretes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41694.     

Wood‐derived phenol novolaks and their wood/epoxy biocomposites

Guaiacol novolak (GCN) and wood‐tar creosote novolak (WCN) were synthesized by the reactions of wood‐derived guaiacol and creosote with formalin, respectively, and used as hardeners of sorbitol polyglycidyl ether (SPE). Thermal and mechanical properties of the cured resins (SPE‐GCN and SPE‐WCN) and their biocomposites with wood flour (WF) were compared with those of the materials prepared by using a petroleum‐based phenol novolak (PN). Although tan δ peak temperatures of SPE‐GCN and SPE‐WCN were lower than that of SPE‐PN, that (58.5–70.8°C) of SPE‐GCN/WF(40–50 wt %) was higher than that (56.6–57.0°C) of SPE‐PN/WF(40–50 wt %). Tensile moduli of all the biocomposites increased by the addition of WF, while tensile strengths were rather reduced. When the biocomposites with the same WF content were compared, tensile modulus of SPE‐GCN/WF was higher than that of SPE‐PN/WF. The 5% weight loss temperatures (346–291°C) of SPE‐GCN and SPE‐GCN/WF were comparable to those (338–284°C) of SPE‐PN and SPE‐PN/WF. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41347.     

Mechanical and thermal properties of novel rubber‐toughened epoxy blend prepared by in situ pre‐crosslinking

A novel method is used for preparing liquid rubber‐toughened epoxy blend, in which an initiator was added to the liquid rubber–epoxy mixture to initiate crosslinking reaction of liquid rubber, and then curing agent was added to form the thermoset. Two epoxy blends with carboxyl‐terminated butadiene‐acrylonitrile copolymers were prepared using traditional and novel methods respectively. Results indicated that the novel rubber‐toughened epoxy blend exhibited much better mechanical properties than its traditional counterpart. The morphologies of the blends were explored by transmission electron microscopy (TEM), it was revealed that the use of the novel method formed a local interpenetrating network structure in the blend, which substantially improved the interfacial adhesion. The impact fracture surfaces of the two blends were observed by scanning electron microscopy (SEM) to explore the toughening mechanism, it was found that crack pinning was the major toughening mechanism for the novel rubber‐toughened epoxy blend. Dynamic mechanical analysis (DMA) was applied to determine the T_g values of the blends, which were found to be close. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41110.     

Preparation and properties of transparent zinc oxide/silicone nanocomposites for the packaging of high‐power light‐emitting diodes

New transparent zinc oxide (ZnO)/silicone nanocomposites with outstanding integrated properties, including a high UV‐shielding efficiency and transparency, bigger thermal conductivity, and lower dielectric constant, were successfully developed; they were prepared by the uniform dispersion of organic modified nano‐ZnO in a silicone matrix through in situ polymerization. The ZnO precursor was prepared by a direct precipitation method, which was then calcinated at different temperatures to produce nano‐ZnO with various morphologies and sizes. The effects of the size, surface nature, and content of nano‐ZnO on the key properties (e.g., optical and dielectric properties, thermal conductivities) of the composites were systematically investigated. The results show that the organic nano‐ZnO prepared by 3‐methacryloxypropyltrimethoxysilane can increase the dispersion of nano‐ZnO in silicone resin, and the interfacial adhesion between inorganic and organic phases, and consequently improve the integrated properties of nanocomposites. The increase of the particle content and size of ZnO in composites can lead to high thermal conductivity and UV‐shielding efficiency but lower visible‐light transparency, so there is an optimum content and size of ZnO in composites to obtain the best integrated properties of the composites. Specifically, the nanocomposite containing 0.03 wt % organic nano‐ZnO with an average size of 46 ± 0.4 nm not only had a high visible‐light transparency, UV‐shielding efficiency, and thermal conductivity but also possessed a low dielectric constant and loss and met the requirements of high‐performance electronic packaging for high‐power light‐emitting diodes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Stress relaxation behavior of starch powder‐epoxy resin composites

The purpose of the present study is to investigate the quasi‐static and the viscoelastic behavior of epoxy resin reinforced with starch powder. An increase in the elastic modulus on the order of 42% was achieved; a behavior that was predicted by the modulus prediction model (MPM). Next, the composite was subjected to flexural relaxation experiments, in order to determine the relaxation modulus, at different filler‐weight fractions and flexural deflections imposed. The viscoelastic models of the standard linear solid, the power law model and the residual property model (RPM) were applied in order to simulate/predict the stress relaxation curves. Predicted values derived from the application of the above models were compared to each‐other as well as to respective experimental findings. From the above comparison it was proved the superiority of the RPM model in predicting both the linear and the nonlinear viscoelastic response of the materials investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41697.     

PET interleaving veils for improved fracture toughness of glass fibre/low‐styrene‐emission unsaturated polyester resin composites

The use of interleaved polyethylene terephthalate (PET) veils to increase the interlaminar fracture toughness of glass fiber‐reinforced, low‐styrene emission, unsaturated polyester resin composites, was investigated. PET, being chemically similar to the unsaturated polyester resin, was expected to exhibit good wetting and strong interaction with the matrix. Composite laminates were manufactured by hand lay‐up, with the veil content varying up to 7%. The effects of PET veils on the interlaminar shear strength, flexural strength, flexural modulus, glass transition temperature, damping parameters, and Mode‐I interlaminar fracture toughness of the composite were studied. The veils were found to enhance most of these properties, with only minor negative effects on flexural stiffness and T_g. The PET/resin bonding did indeed prove to be strong, but the enhancement of fracture toughness was not as much as expected, because of the weaker glass/resin interface providing an alternative crack propagation path. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42877.