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.     

Anisotropically ordered liquid crystalline epoxy network on carbon fiber surface

Summary Anisotropic orientation of liquid crystalline epoxy(LCE) resin on carbon fiber(CF) surface was investigated and it was correlated with curing behavior and thermomechanical properties of LCE. Anisotropic orientation of a LCE resin was spontaneously induced on CF surface along a long molecular axis of CF during curing and the anisotropic orientation was maintained after curing. Curing of LCE was accelerated by alignment of LCE on CF and anisotropic orientation of LCE enhanced dynamic modulus of CF reinforced LCE composites.     

Non‐fickian three‐dimensional hindered moisture absorption in polymeric composites: Model development and validation

A new, three‐dimensional, anisotropic non‐Fickian diffusion model is developed to characterize moisture absorption in polymeric composites. The new hindered diffusion model extends the classical Fickian theory to include the effects of the interaction of diffusing molecules with the chemical and physical structure of polymeric composites. The numerical solution of the hindered diffusion model is obtained for a three‐dimensional, anisotropic domain by using a forward‐time, centered‐space finite difference technique. The moisture weight gain over time predicted by the model is shown to mimic a wide variety of anomalous absorption behavior, often exhibited by anisotropic composite laminates. The accuracy of the numerical solutions is verified by comparing the results to known analytical solutions of a one‐dimensional, “Langmuir‐type” diffusion model and for the limiting case of the three‐dimensional Fickian model. The utility of the proposed hindered diffusion model is demonstrated by accurately recovering the absorption behavior of three different material systems reported in literature. First, it is shown that the hindered diffusion model can accurately predict the moisture absorption data for unidirectional glass‐reinforced epoxy plates of varying dimensions exposed to a relative humidity of 80%. Second, the one‐dimensional version of the model is applied to experimental moisture absorption data for isotropic epoxy resin samples of different thicknesses. Anomalous effects due to sample thickness reported in the original article are accurately captured. Third, the proposed model is shown to be more accurate than a two‐stage diffusion model applied to moisture absorption data obtained from a woven 3‐ply carbon fiber reinforced bismaleimide composite. POLYM. COMPOS., 34:1144–1157, 2013. © 2013 Society of Plastics Engineers     

Tribological behavior of short‐fiber‐reinforced polyimide composites under dry‐sliding and water‐lubricated conditions

Polyimide composites reinforced with short‐cut fibers such as carbon, glass, and quartz fibers were fabricated by the polymerization of monomer reactants process. The mechanical properties of the composites with different fiber contents were evaluated. The friction and wear properties of the polyimide and its composites were investigated under dry‐sliding and water‐lubricated conditions. The results indicated that the short‐carbon‐fiber‐reinforced polyimide composites had better tensile and flexural strengths and improved tribological properties in comparison with glass‐fiber‐ and quartz‐fiber‐reinforced polyimide composites. The incorporation of short carbon fibers into the polyimide contributed to decreases in the friction coefficient and wear rate under both dry and water‐lubricated conditions and especially under water lubrication because of the boundary lubrication effect of water. The polyimide and its composites were characterized by plastic deformation, microcracking, and spalling under both dry and water‐lubricated conditions, which were significantly abated under the water‐lubricated condition. The glass and quartz fibers were easily abraded and broken; the broken fibers transferred to the mating metal surface and increased the surface roughness of mating stainless steel, which led to the wear rate increasing for the glass‐fiber‐ and quartz‐fiber‐reinforced polyimide composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Preparation and properties of multi‐walled carbon nanotubes/carbon fiber/epoxy composites

Multi‐walled carbon nanotubes/carbon fiber (MWCNTs/CF) hybrid fillers are employed to prepare MWCNTs/CF/epoxy composites. Results reveal that a great improvement of the thermal conductivities of the epoxy composites with the addition of MWCNTs/CF hybrid fillers, and the thermal conductivity of the MWCNTs/CF/epoxy composites is 1.426 W/mK with 8 vol% treated MWCNTs/CF hybrid fillers (5 vol% MWCNTs + 3 vol% CF). Both the flexural and impact strength of the MWCNTs/CF/epoxy composites are increased firstly, but decreased with the excessive addition of MWCNTs. The flexural and impact strength of the MWCNTs/epoxy composites are optimal with 2 vol% MWCNTs. For a given MWCNTs/CF hybrid fillers loading, the surface treatment of MWCNTs/CF hybrid fillers can further increase the thermal conductivities and mechanical properties of the MWCNTs/CF/epoxy composites. POLYM. COMPOS., 35:2150–2153, 2014. © 2014 Society of Plastics Engineers     

Incorporation of epoxidized soybean oil as co‐matrix in epoxy resin toward developing plastisol/particulate toughened glass fiber composites

Epoxidized soybean oil was incorporated as a co‐matrix into an epoxy resin, and the hybrid resin system was used for preparing glass fiber‐reinforced composites. Effect of addition of poly(vinyl chloride) plastisol and selected particulate fillers (fly ash and wood flour) to epoxy/epoxidized soybean oil matrix on mechanical and water uptake properties of glass fiber‐reinforced composites were studied. Fourier transform infrared spectroscopy was used to reveal the curing state of these composites. It was observed that tensile strengths and moduli decreased with the inclusion of all additives. However, addition of poly(vinyl chloride) plastisol, fly ash, and wood flour particulate fillers showed significant increase in impact strengths compared with neat epoxy composite in a synergistic manner. Water uptake results of the composites were found to be in good agreement with ? OH peak intensities obtained from Fourier transform infrared spectroscopy. Finally, acousto‐ultrasonic nondestructive technique was successfully used to assess damage states and to relate stress wave factors with tensile strength properties of modified epoxy‐based glass fiber composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40586.     

Properties of carbon fiber reinforced poly(vinylidene fluoride)‐based friction materials of ultrasonic motors

In order to improve output properties and anti‐irradiation capability of ultrasonic motors (USMs), which are driven by friction forces of friction material between the stator and rotor, a type of friction material is fabricated by composite materials consist of carbon fiber (CF) and polyvinylidene fluoride (PVDF). The effects of different contents of CF on the mechanical and tribological properties of PVDF‐based friction materials are studied, and the mechanical features of the relative USMs are measured. Further, the worn surface morphology of PVDF composites is observed by means of scanning electron microscope and the wear mechanisms are also discussed. In addition, the anti‐irradiation capability of the type of friction materials is measured by the γ‐ray irradiation at room temperature environment with the total radiation dose of 4.0X rad (Si). The experimental results show that the incorporation of CF into PVDF can effectively improve the friction and wear properties of the friction materials, and the mechanical properties of TRUM‐60 used by relative PVDF composites are also increased with the increase of CF. For TRUM‐60, both the no‐load speed and holding torque of the USMs were high, and the wear of friction material was lowest, when the CF content is 15 wt%. The experiment results also show that this PVDF‐based friction material has a good anti‐irradiation property. Therefore, the composite materials consist of CF and PVDF are beneficial for the applications in USMs, especially for some radiation environment. POLYM. COMPOS., 37:547–552, 2016. © 2014 Society of Plastics Engineers     

Flammability and thermomechanical properties of dianhydride‐modified polybenzoxazine composites reinforced with carbon fiber

Composites based on carbon fiber (CF) and benzoxazine (BA‐a) modified with PMDA were investigated. The flammability of the carbon fiber composites was examined by limiting oxygen index (LOI) and UL‐94 vertical tests. The LOI values increased from 26.0 for the CF/poly(BA‐a) composite to 49.5 for the CF‐reinforced BA‐a/PMDA composites as thin as 1.0 mm and the CF‐reinforced BA‐a/PMDA composites were also achieved the maximum V‐0 fire resistant classification. Moreover, the incorporation of the PMDA into poly(BA‐a) matrix significantly enhanced the T_g and the storage modulus (E') values of the CF‐reinforced BA‐a/PMDA composites rather than those of the CF/poly(BA‐a). The T_g values and storage moduli of the obtained CF‐reinforced BA‐a/PMDA composites were found to have relatively high value up to 237°C and 46 GPa, respectively. The CF‐reinforced BA‐a/PMDA composites exhibited relatively high degradation temperature up to 498°C and substantial enhancement in char yield with a value of up to 82%, which are somewhat higher compared to those of the CF/poly(BA‐a) composite, i.e., 405°C and 75.7%, respectively. Therefore, due to the improvement in flame retardant, mechanical and thermal properties, the obtained CF‐reinforced BA‐a/PMDA composites exhibited high potential applications in advanced composite materials that required mechanical integrity and self‐extinguishing property. POLYM. COMPOS., 34:2067–2075, 2013. © 2013 Society of Plastics Engineers     

Low‐velocity impact response and compression after impact assessment of recycled carbon fiber‐reinforced polymer composites for future applications

The influence of recycling on the impact damage resistance of recycled carbon fiber‐reinforced polymer (CFRP) composites was investigated using low‐velocity impact and compression after impact (CAI) tests. The relationships among load, force, and time were analyzed to gain insight into the damage characteristics of three types of composite laminate: virgin CF‐reinforced polymer (V‐CFRP), recycled CF‐reinforced polymer (R‐CFRP), and treated recycled CF‐reinforced polymer (TR‐CFRP). Special emphasis was placed on evaluating the extent of damage and the residual mechanical properties as affected by three different fiber surface states. Substantial differences were noted in the shape, area, and damage mode of impact using ultrasonic c‐scanning, photography, and scanning electron microscopy (SEM). V‐CFRP indicated significant improvement in impact damage resistance in the form of less damage, higher residual strength, and greater shear failure angle. Damage resistance was improved up to 80% of V‐CFRP by surface cleaning while R‐CFRP is 50% of V‐CFRP. Shear failure angle of 16° was attained from R‐CFRP and it was increased to 24° when the recycled fibers were cleaned. The result of SEM showed that there was less delamination of TR‐CFRP compared with R‐CFRP. This work proves that the low‐velocity impact response of recycled composites can rival that of virgin composites, while providing a basis for future applications of recycled carbon in many fields. POLYM. COMPOS., 35:1494–1506, 2014. © 2013 Society of Plastics Engineers     

Effects of sizing materials on the properties of carbon fiber‐reinforced polyamide 6,6 composites

This article aims to study the effect of the sizing materials type on the mechanical, thermal, and morphological properties of carbon fiber (CF)‐reinforced polyamide 6,6 (PA 6,6) composites. For this purpose, unsized CF and sized CFs were used. Thermogravimetric analysis was performed, and it has been found that certain amounts of polyurethane (PU) and PA sizing agents decompose during processing. The effects of sizing agent type on the mechanical and thermomechanical properties of all the composites were investigated using tensile, Izod impact strength test, and dynamic mechanical analysis. Tensile strength values of sized CF‐reinforced composites were higher than that of unsized CF‐reinforced composites. PA and polyurethane sized CF‐reinforced composites exhibited the highest impact strength values among the other sized CF‐reinforced composites. PU and PA sized CF‐reinforced composites denoted higher storage modulus and better interfacial adhesion values among the other sizing materials. Scanning electron microscope studies indicated that CFs which were sized with PU and PA have better interfacial bonding with PA 6,6 matrix among the sized CFs. All the results confirmed that PA and PU were suitable for CF's sizing materials to be used for PA 6,6 matrix. POLYM. COMPOS., 34:1583–1590, 2013. © 2013 Society of Plastics Engineers     

Silane coupling agent modification on interlaminar shear strength of carbon fiber/epoxy/nano‐CaCo3 composites

Four different types of composites were prepared based on unmodified and modified epoxy matrices: (A) unmodified epoxy/carbon fiber composites, (B) modified epoxy/carbon fiber composites by silane coupling agent/nano‐CaCO₃ master batch, (C) modified epoxy/carbon fiber composites by nano‐CaCO₃ particles directly, and (D) modified epoxy/carbon fiber composites by nano‐CaCO₃ particles and silane coupling agent together. The interlaminar shear strength (ILSS) of the carbon fiber‐reinforced composites was investigated. The results show that the silane coupling agent/nano‐CaCO₃ master batch can increase the ILSS to the highest degree. Nevertheless, Sample D, i.e., modified by nano‐CaCO₃ particles and silane coupling agent together, even presents a decrease of the ILSS. The integration effect of silane coupling agent/nano‐CaCO₃ master batch was concluded. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Influence of two carbon plies on adhesion of unidirectional flax‐fibers reinforced epoxy composites

In this work, we undertook a comparative study of the dynamic dielectric analysis of two unidirectional epoxy composites: flax‐fiber‐reinforced epoxy and flax/carbon‐fiber‐reinforced epoxy (FCFRE). In both composites, three relaxation processes were identified. The first one is the water dipoles polarization imputed to the presence of polar water molecules in flax fiber. The second relaxation process associated with conductivity occurs as a result of the carriers charges diffusion noted for high temperature above glass transition and low frequencies. As for the third dielectric relaxation associated with the interfacial polarization effect is attributable to the accumulation of charges at the fibers/matrix interface. The presence of two carbon plies in the reinforcement gives rise to two interfacial polarization effects in the FCFRE composite. The analysis of the Maxwell–Wagner–Sillars and the water dipoles polarizations using the Havriliak–Negami model revealed that the presence of two plies of carbon can locally decrease the adhesion of flax fibers in the matrix. This analysis was supported by the thermal properties using a differential scanning calorimety and the mechanical properties using a short beam shear test. POLYM. COMPOS., 241–253, 2016. © 2014 Society of Plastics Engineers     

The effect of surface treatments on the mechanical properties of basalt‐reinforced epoxy composites

Basalt fiber is an emerging alternative reinforcement to glass or carbon depending upon the application. An important contributing parameter to ultimate performance of any composite is the fiber–‐matrix interface, to which toughness and compressive strength are intimately related. To better understand this matrix fiber interaction in controlling properties, we compared different modification strategies and the impact upon the properties of composites. Strategies focussing upon mechanical interlocking through increased surface roughness and covalent chemical bonding using sol/get methods were explored. Combined methods were also used to explore synergistic behavior as well as the use of aliphatic triethylenetetramine (TETA) to react with any covalently attached epoxy groups. Results from single ply composites showed that when the properties were fiber or fiber/matrix dominated, the sol/gel or epoxy silane method gave the largest improvement in ultimate tensile strength increasing 66% and 27% for uni‐weave 0° and 45° laminas. The combined surface modification methods exhibited increases of 45% and 13% for the same laminas. When properties were matrix dominated, the combined strategies produced the highest improvements in ultimate tensile strength of about 55% compared with 37% for sol/gel modification. For 16‐ply plain weave laminates, epoxy silane surface treatments produced the greatest improvements in compressive and interlaminar shear strengths, increasing 52% and 21%, respectively. This correlated with fiber‐ and fiber/matrix‐dominated results from single ply laminas. The combined treatment using TETA however decreased shear and compressive strength by about 20%, while scanning electron microscopy (SEM) evaluation and dynamic mechanical thermal analysis (DMTA) attributed this to increased resin ductility and plasticization. © 2013 Society of Plastics Engineers     

Rate‐dependent constitutive equations for carbon fiber‐reinforced epoxy

A rate‐dependent constitutive model for carbon fiber‐reinforced polymers was developed by assuming that the rate‐dependent characteristics of the composite could be described by stress relaxation of the polymer matrix. Relaxation functions in longitudinal, transverse, and in‐plane shear modes were derived in terms of separate matrix and fiber properties and the rules of mixture. The epoxy was represented as two Maxwell elements in parallel with a linear elastic spring, while the carbon was modeled as a linear elastic spring. The rate‐dependent, laminate stiffness matrix for a unidirectional IM6G/3501–6 carbon/epoxy laminate was found by fitting the rate‐dependent constitutive equations to material test data at constant strain rates ranging from 0.01 to 2,500 s⁻¹. The transient deformation response of a [(0₈/90₈)₂/0 ₈]_s IM6G/3501–6 carbon/epoxy composite laminate under dynamic in‐plane loading could be predicted within 5% of experimental data using this laminate stiffness matrix. The rate‐dependent constitutive equations were also incorporated into LS‐DYNA3D via a user‐defined material subroutine and used to predict the transient response of a 32 ply AS4/3501–6 carbon/epoxy laminate under projectile loading. The maximum contact force between the projectile and laminate was found to be 7% higher than the experimental data. POLYM. COMPOS. 27:513–528, 2006. © 2006 Society of Plastics Engineers.     

Interfacial shear strength in carbon fiber‐reinforced poly(phthalazinone ether ketone) composites

We studied interfacial shear strength (IFSS) in carbon fiber (CF)‐reinforced poly (phthalazinone ether ketone) (PPEK) composites system, with emphasis on the influence of forming temperature of composite and sizing agent on CFs. To obtain apparent IFSS of CF‐reinforced PPEK composites shaped at various forming temperatures ranged from 20 up to 370°C, microbond test was carried out at single‐fiber composites. Results of microbond test showed that apparent IFSS was directly proportional to the difference between the matrix solidification temperature (forming temperature) and the test temperature and approximately 80% of the apparent IFSS in CF/PPEK composite system was attributed to residual radial compressive stress at the fiber/matrix interface. By sizing CF with sizing agent, the wettability of the fiber by the matrix was improved and the final apparent IFSS was also improved. POLYM. COMPOS., 34:1921–1926, 2013. © 2013 Society of Plastics Engineers     

Toughened carbon fiber fabric‐reinforced pCBT composites

Toughened carbon fiber‐fabric reinforced polymerized cyclic butylene terephthalate (pCBT) composites were obtained by chemical modification of cyclic butylene terephthalate (CBT) with small amounts of epoxy resin and isocyanates as chain extenders. Homogeneous CBT/epoxy and CBT/isocyanate blends were prepared by melt blending the components in a lab‐scale batch mixer at low temperatures and high shear rate. Melt blending was stopped before the ring‐opening polymerization of CBT could start. The modified CBT was the starting material for carbon fiber fabric‐reinforced pCBT composites (fiber content at about 65 wt%) which were prepared by ring‐opening polymerization during compression molding using a simple powder prepreg method. Interlaminar shear strength, flexural strength, and failure strain of the chemically modified composites increased up to 60% with respect to unmodified pCBT composites. Nevertheless, the flexural moduli slightly decreased due to the toughening effect of the chain extender on the pCBT matrix. Drop weight impact tests revealed that the energy absorption of the modified composites was relatively higher as compared to unmodified pCBT composites. POLYM. COMPOS., 37:1453–1460, 2016. © 2014 Society of Plastics Engineers     

Fiber hybrid polyimide‐based composites reinforced with carbon fiber and poly‐p‐phenylene benzobisthiazole fiber: Tribological behaviors under sea water lubrication

Fiber hybrid polyimide‐based (PI‐based) composites reinforced with carbon fiber (CF) and poly‐p‐phenylene benzobisthiazole (PBO) fiber of different volume fractions were fabricated by means of hot press molding technique, and their mechanical properties and tribological behaviors under sea water lubrication were systematically investigated in relation to the synergism of CF and PBO fiber. Results showed that the incorporation of CF or PBO fiber improved the tensile strength, hardness, and wear resistance of PI. More importantly, because of the synergistic enhancement effect between CF and PBO fiber on PI matrix, the combination of 10%CF and 5%PBO fiber reinforced PI‐based composite had the best mechanical and tribological properties, showing promising application in ocean environment. POLYM. COMPOS., 37:1650–1658, 2016. © 2014 Society of Plastics Engineers     

The effect of hydroxyl‐terminated polybutadiene‐grafted carbon fiber on the impact performance of carbon fiber–epoxy resin composites

Carbon fiber (CF) containing 1.4 and 2.1 mmol/g of —COOH and —OH groups, respectively, was functionalized by using an excess of tolylene‐2,4‐diisocyanate. The NCO‐modified CF was submitted to a graft reaction with hydroxyl‐terminated polybutadiene (HTPB). The HTPB‐grafted carbon fiber was employed as reinforcing agent for epoxy resin‐based composites. The presence of the flexible HTPB at the interface between the fiber and the matrix resulted in a substantial improvement on impact strength. Additional improvement on toughness was achieved by using epoxy matrix containing dispersed phase of HTPB. The composite morphology was also studied by scanning electron microscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1424–1431, 1999     

Quasi‐static and dynamic experiment investigations on the crashworthiness response of composite tubes

Crashworthiness performance of carbon and glass composite tubes have been comprehensive investigated under quasi‐static and dynamic axial crush testing. In this study, collapse modes and specific energy absorption (SEA) of different ply orientation of carbon fabric composites and unidirectional glass tubes were analyzed. For the weaker tensile strength and bending strength of glass composites, crack propagated approximately perpendicular to the fiber direction when the ply angle was small. Large amount of fibers breakage made the specific energy absorption over 80 kJ/kg under dynamic load. Thickness effect had inverse influence on SEA under different impact rate. The specific energy absorption declined as tube thickness increased under dynamic crush tests, however, increased under quasi‐static tests. Hybridization of glass/carbon tubes and carbon/carbon composites were analyzed by increased the axial fiber content. It was found that hybridization tubes of G803/3234 fabric and G827/3234 axial tapes with higher G827/3234 content present excellent energy‐absorption capability under dynamic and quasi‐static tests for all specimens tested. POLYM. COMPOS., 34:1099–1109, 2013. © 2013 Society of Plastics Engineers     

Preparation of multiscale graphene oxide‐carbon fabric and its effect on mechanical properties of hierarchical epoxy resin composite

Graphene oxide (GO) was used to modify the surface of carbon fiber layers through electrophoretic deposition, forming a multiscale reinforcement fabric. By adjusting the experimental parameters, the resulting GO‐carbon fabric showed productive and homogenous distribution of thin and less‐agglomerate GO platelets on carbon fiber surface, remarkably enlarging the surface area and roughness of carbon fabric. To investigate the effect of GO sheets on composites, GO‐carbon fabric and carbon fabric‐reinforced hierarchical epoxy resin composites were respectively manufactured. Mechanical tests demonstrated that after introducing GO flakes on carbon fabric, both the flexural strength and interlaminar shear strength of composite had achieved an increase, especially the interlaminar shear strength rising by 34%. Through fractography analysis, it was found that in pure carbon fabric‐reinforced epoxy composite, the fiber/matrix debonding fracture mechanism predominated, while after the GO decoration on carbon fiber surface, the composite featured a stronger interfacial bonding, leading to the enhancement in mechanical properties of hierarchical epoxy resin composite. POLYM. COMPOS., 37:1515–1522, 2016. © 2014 Society of Plastics Engineers