Carbon Fiber Reinforced Polyimide Composites Research Articles

Raman mapping microspectroscopy of the effects of cryogenic cycling on the interfacial micromechanics of carbon fiber-reinforced polyimide composites

Raman mapping microspectroscopy of the effects of cryogenic cycling on the interfacial micromechanics of carbon fiber-reinforced polyimide composites

Raman mapping microspectroscopy of the effects of cryogenic cycling on the interfacial micromechanics of carbon fiber-reinforced polyimide composites

Raman mapping microspectroscopy was then used to investigate the interfacial stress distributions of the films during different cryogenic-room temperature cycles (-198-25 °C, 0-300 cycles). It was found that the micro stress of CNT-PI films (around 175 MPa) had no significant changes even after 300 cycles. The cryogenic cycling had very little effect on the internal stress, indicating that PI had a good low temperature resistance. For the CF/CNT-PI films, the micro stress distributions of CFs, interface, and matrix regions were successfully obtained. It was found that the CFs bear a greater stress than the matrix, showing that CFs had always been the major stress bearer, confirming the strengthening effect of CFs. When the CF/CNT-PI films were cycled fewer than 250 times, the effect of cryogenic cycling on the micro stress was insignificant. But once the number of cycles reached 300, the compressive stresses on the fiber and interface increased by 21% and 12.9%, respectively, implying a deterioration of the mechanical properties. By Raman mapping, the micro-mechanical distributions of the reinforced material, matrix and interface of the composites under cyclic temperature changes were effectively quantified. This is therefore an effective method for evaluating the safety of composite materials.

Effect of carbon nanotubes modification on bending fatigue properties of carbon fiber reinforced polyimide composites

Polyimide-based composites have been widely used as structural materials in aerospace and automotive industries. In the present work, carbon fiber fabric reinforced polyimide composites (CF/PI) were modified by carbon nanotubes (CNTs). The monotonic bending properties and bending fatigue performance of CNTs modified CF/PI were investigated at room temperature. Both bending strength and bending modulus of CF/PI can be increased by CNTs. The CNTs filler could inhibit crack initiation and retard crack propagation. The fatigue resistance is significantly enhanced in CNTs modified CF/PI, which is related to the CNTs enhanced matrix crack resistance and fiber/matrix debonding.

Topology and structure analysis of carbon fiber-reinforced polyimide composites

This paper describes the production of carbon fiber / high-performance polyimide prepregs and the study of prepreg samples quality by scanning electron microscopy, atomic-force electron microscopy and scanning ion-conductance microscopy. The prepreg samples were produced using a laboratory-designed setup by impregnation of carbon fiber with a polyimide solution. The study of the prepreg structure made it possible to establish the connection between polymer matrix composition and quality of carbon fiber impregnation. Thus, the study shows that the polymer matrix composition containing aliphatic fragment and quaternary carbon atom produces the best performance prepreg suitable for FDM 3D printing.

High temperature phenylethynyl-terminated imide oligomers derived from asymmetric diphenyl ether diamines for resin transfer molding

Resin transfer molding (RTM) require phenylethynyl-terminated imide oligomers (PETIs) to exhibit low melt temperatures and better melt stability. To decrease the melt temperatures of PETIs and improve their resin transfer moldable processability, asymmetric 4,4′-diaminodiphenyl ether substituted by fluorine (F-ODA), trifluoromethyl group (3F-ODA) or phenyl group (p-ODA) were introduced. Asymmetric molecular structure and substituent groups decrease the melt temperatures of PETIs, endowing PETIs with the wider processing temperature windows and low minimum melt viscosity (<1 Pa s). These polyimides show pot lives of 30–60 min at 260–280 °C. Furthermore, the effects of backbone structure on melt fluidity of imide oligomers were discussed by the calculation of viscous activation energy (Ea,η) and analysis of Molecular Dynamics. PETI-3F and PETI-P based on 3F-ODA and p-ODA exhibit low and stable melt viscosities (<1 Pa s) at 250–270 °C and 260–270 °C for 4 h respectively, enabling the successful fabrication of carbon fiber reinforced polyimide composites via RTM process. After cured at 380 °C, the thermosets of PETI-3 and PETI-4 show high Tg of 412 °C and 402 °C and good thermal stability (Td5>550 °C). Cured PETI-3 and PETI-4 also show good mechanical properties (tensile strength >50 MPa). In comparison with p-ODA, 3F-ODA could provide PETIs with superior resin transfer moldable processability and higher heat-resistance and is more suitable to synthesize PETIs for RTM application, because of better balance between polymer segmental mobility and polymer chain packing.

Hygrothermal effect on mechanical behaviours and failure mechanisms of single-lap countersunk-screwed CFRPI-metal joint

This paper seeks to probe experimentally and numerically hygrothermal effect on mechanical behaviors and failure mechanisms of single-lap countersunk-screwed CFRPI (carbon fiber reinforced polyimide composite)-metal joints. Accelerated moisture absorption tests were conducted on CCF300/AC721 plate until effective moisture equilibrium, and quasi-static tension tests were performed on single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints in RD (room temperature and dry), RW (room temperature and wet) and EW (elevated temperature +55 °C and wet) environments, respectively. From the experiment results, moisture and temperature impacts were analyzed and discussed. By considering hygrothermal-mechanical interaction, non-linear shear constitutive relationship and complicated failure modes, an improved PDM (progressive damage model) was devised to simulate mechanical behaviors and failure mechanisms of single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints. Predictions agree well with the experimental results, demonstrating the effective use of new PDM. It is shown from experimental and numerical results that delamination around screw hole is likely the primary reason for final failure of joint, and the negative hygrothermal effect on joint performance mainly contributes to the decrease in inter-laminar properties of composite laminate with the increase in moisture and temperature. HIGHLIGHTS Accelerated moisture absorption tests were conducted on CCF300/AC721 plate, followed by quasi-static tension tests on single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints in the RD, RW and EW environments. An improved PDM was devised to simulate mechanical behaviours and failure mechanisms of single-lap countersunk-screwed CCF300/AC721-30CrMnSiA joints, and the predictions agree well with the experimental results. Research results demonstrate that hygrothermal effect likely contributes to the decrease in inter-laminar properties of composite laminate with moisture and temperature, ultimately deteriorating joint performance.

Long-term Thermo-oxidative Degradation Modeling of a Carbon Fiber Reinforced Polyimide Composite: Multistep Degradation Behaviors and Kinetics

This study aims to disclose the thermo-oxidative degradation behaviors and kinetics of a carbon fiber reinforced polyimide (CFRPI) composite for modeling of the long-term degradation process. The degradation behaviors were revealed through off-gas products analysis, and the overall kinetic interpretation was achieved from study of the mass-loss curves recorded under dynamic conditions. It was found that thermo-oxidative degradation of the CFRPI composite was a multistep process, which included four main reaction steps. Since most kinetic analysis methods were derived from simple reactions described by a single kinetic triplet, they cannot be applied reliably to such a process. Therefore, we firstly separated the four overlapped reaction steps by peak fitting of derivative thermogravimetric curves using Frasier-Suzuki equation considering the asymmetrical nature of kinetic curves, and subsequently analyzed each individual reaction employing Friedman method and experimental master-plots method. Four sets of kinetic triplets were determined to characterize the entire degradation process. The validity of four corresponding kinetic triplets was confirmed by perfect simulation of mass-loss curves recorded at both dynamic conditions used in kinetic analysis and entirely different isothermal conditions. Finally, modeling of long-term aging at 400 °C of the CFRPI composite was successfully achieved based on these kinetic triplets. The predicted mass loss and flexural property correlated well with experimental results. This study can serve as a basis for rapid evaluation of the long-term durability of the CFRPI composite in various application environments.

Preparation of carbon fiber-reinforced polyimide composites via in situ induction heating

Induction heating, a direct and contactless heating method, is generally more rapid and energetically more efficient than other heating methods used. In this work, we report the high-temperature imidization of carbon fiber/polyimide (PI) composites using an in situ induction heating method. Furthermore, we compare the advantages of the method to a conventional thermal procedure. The formed composites feature almost identical imidization rates, glass transition temperatures, and thermal oxidative stabilities cured at the same heating temperatures using a different heating process. Upon doping with ferriferous oxide, the ability of the magnetic nanoparticles in an alternating current field was studied to further drive the heating process and increase the rising and cooling time. The in situ induction heating process proves to be a powerful method for the high-temperature polymerization of high-performance thermoplastic composites, particularly for a PI matrix.

The effect of coupling agents on the mechanical properties of carbon fiber-reinforced polyimide composites

Carbon fiber (CF)-reinforced polyimide (PI) has been widely used in many engineering fields because of its high specific strength and stiffness. However, PI does not adhere well with CFs because it has low free surface energy. In addition, high viscosity in the melted phase causes poor impregnation. In this study, surface treatment methods, that is, coupling agents (CAs) with plasma treatment on CFs, were applied to increase the interfacial strength between the CFs and the PI matrix. The modified CF surfaces were analyzed by X-ray photoelectron spectroscopy and scanning electron microscopy. To analyze the effectiveness of the surface treatment method, the interlaminar shear strength (ILSS) was measured using the three-point bending test. From the test results, the ILSS of the specimens treated with the silane CA after the plasma treatment increased by 48.7% compared with the untreated specimens.

The effect of titanium dioxide on the tribological properties of carbon fiber-reinforced polyimide composites

This study examined the effect of titanium dioxide (TiO2) dispersion on the tribological properties of carbon fiber (CF)-reinforced–polyimide (PI) matrix (CF/PI) composites. Nanocomposites were prepared through compression molding as milled CF/PI mixtures without further melt mixing. The incorporation of TiO2 leads to a significant improvement in friction and wear properties of the CF/PI composite. The scratches on the worn surface of the CF/PI composite filled with TiO2 are considerably reduced. We can see a relatively smooth, uniform, and compact worn surface, which is in good agreement with the considerably increased wear resistance of the CF/PI composite.

Influence of laminate lay-up on oxidation and damage growth: Isothermal aging

The thermo-oxidative behavior of a composite is significantly different from that of the constituents as the composite microstructure, including the fiber/matrix interphase/interface, architecture and ply lay-up introduce anisotropy in the diffusion and oxidation behavior. In this work, light microscopy and scanning electron microscopy techniques are used to characterize the oxidative process in laminated carbon fiber-reinforced polyimide composites. Four different composites are considered, namely, unidirectional [0] 16T, quasi-isotropic [0/±45/90] 2S, cross-ply [0/90] 4S, and angle-ply [±45] 2S laminates. The observed anisotropy in composite oxidation is explained by carefully monitoring the development and growth of damage through the use of fluorescence imaging using dye impregnation. It is shown that the oxidation behavior of a laminate is strongly dependent on the ply stacking sequence, while alternative pathways for transport of oxygen into the interior of the composite are fiber–matrix debonds and matrix cracks that propagate with the oxidation front.

Heterogeneous Thermo-oxidative Behavior of Multidirectional Laminated Composites

This article examines the through-the-thickness heterogeneity observed in oxidation profiles of composite laminates. The effect of ply angle on oxygen diffusivity and the influence of ply stacking sequence on oxidation behavior of isothermally aged multidirectional composites are discussed by correlating experimental observations and a three-dimensional oxidation model. Experimental observations of oxidation growth are made using dark-field optical microscopy, while damage initiation and growth is detected using fluorescence imaging with dye impregnation. Oxidation growth in laminated systems is simulated using a diffusion-reaction-conversion model developed earlier for resin oxidation along with homogenization techniques. Several stacking sequences of carbon fiber-reinforced polyimide composites are studied. The effects of the orthotropy in the diffusivity tensors of each ply and the influence of neighboring ply on oxidation growth are clearly illustrated. The simulation results presented in this article are valid till the onset of damage, beyond which coupling effects between oxidation growth and damage evolution have to be addressed.

Effect of surface oxidation treatment on the tribological performance of carbon fiber reinforced polyimide composites

AbstractThe effect of ozone surface treatment of carbon fibers (CF) on the tensile strength and tribological properties of carbon fiber reinforced polyimide (CF/PI) composite was investigated. Experimental results revealed that the tensile strength of ozone and air oxidation treated CF reinforced PI composite was improved compared with that of untreated composite. Compared with the untreated and air‐oxidated CF/PI composite, the ozone treated composite had the lowest friction coefficient and specific wear rate under given applied load and reciprocating sliding frequency. Ozone treatment effectively improved the interfacial adhesion between CF and PI. The strong interfacial adhesion of the composite made CF not easy to detach from the PI matrix, and prevented the rubbing‐off of PI, accordingly improved the friction and wear properties of the composite.

The tribological properties of acid- and diamine-modified carbon fiber reinforced polyimide composites

Carbon fibers (CFs) were treated by HNO 3 plus diamine modification and incorporated into polyimide (PI) matrix to prepare polymer composites. The friction and wear properties of the PI composites reinforced by untreated and treated carbon fibers (15 wt.%), sliding against GCr15 steel, were studied on an M-2000 model ring-on-block test rig under dry sliding. Experimental results showed that the surface treatment largely reduced the friction and wear of CFs reinforced PI (CFs/PI) composites. The worn surface of CFs/PI composites and the transfer films formed on the surface of the counterpart ring sliding against CFs/PI composites were investigated by SEM. Compared with the untreated ones, the surface modified CFs can enhance the tribological properties of CFs/PI composite efficiently due to the improved adhesion between CFs and PI matrix. The differences in the friction and wear properties of CFs/PI composites are closely related with the sliding condition such as sliding rate and the applied load. Research results show that CFs/PI composites exhibited better tribological properties under higher load and sliding speed.

Preparation and Properties of M40 Carbon Fiber-Reinforced Thermoplastic Polyimide Composites

A series of M40 high modulus carbon fiber-reinforced polyimide (CFRPI) composites are prepared by laminating premolding PI films with unidirectional CF layers. After the imidization processing of premolding PI films is estimated, the effect of CF volume fraction, processing conditions, and PI molecular structure on the properties of CFRPI composites is studied in detail. In addition, SiO2 nanoparticles are added as fillers to the premolding PI films at varying concentrations. The effect of the nanoparticles on the properties of CFRPI composites is also investigated. The surface characteristics of M40 CF are measured by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The thermal and mechanical properties of CFRPI composites are measured by dynamic mechanical thermal analysis, SANS testing machine, scanning electron microscopy, and other techniques. The experimental results show that the properties of CFRPI composites are mainly affected by the premolding PI film and molding conditions. The change of CF volume fraction from 55 to 65% has little effect on the mechanical properties of the CFRPI composites. In addition, flexible PI as a CF sizing improves the interlaminar shear strength, flexural strength, and flexural modulus of CFRPI composites, and the incorporation of SiO2 nanoparticles further improves the properties of CFRPI composites.

Tribological properties of MoS2 and carbon fiber reinforced polyimide composites

The tribological properties of carbon fiber reinforced polyimide (PI) composites with different MoS2 containing sliding against GCr15 steel were comparatively evaluated on an M-2000 model ring-on-block test rig. The wear mechanisms were also comparatively discussed, based on scanning electron microscopic examination of the worn surface of the PI composites and the transfer film formed on the counterpart. It was found that small incorporation of MoS2 was harmful to the improvement of friction and wear behaviors of carbon fiber reinforced PI composites. However, it was found that the increasing filler of MoS2 significantly improved the wear resistance and decreased the friction coefficient of carbon fiber reinforced PI composites. It was also found that the tribological properties of MoS2 and short carbon fiber reinforced PI composites were closely related with the sliding condition such as sliding rate and applied load.

Effect of Solid Lubricant on the Tribological Properties of Polyimide Composites Reinforced with Carbon Fibers

The short carbon fiber reinforced polyimide (PI) composites filled with particulates of graphite were prepared by a heat molding technique. The friction and wear behaviors of PI composites sliding against GCr15 steel rings were evaluated on an M-2000 model ring-on-block test rig. It was found that the filler of graphite can significantly improve the wear resistance and decrease the friction coefficient of the PI composites. It was also found that the tribological properties of the short carbon fiber reinforced PI composites filled with graphite are closely related with the sliding condition such as sliding rate and the applied load.

The effect of carbon fiber content on the friction and wear properties of carbon fiber reinforced polyimide composites

AbstractThe current study examines the tribological performance of polyimide and carbon fiber reinforced polyimide (CF/PI) under dry sliding condition. Different contents of carbon fibers were employed as reinforcement. All filled and unfilled polyimide composites were tested against CGr15 ball and representative testing was performed. The effects of carbon fiber content on tribological properties of the composites were investigated. The worn surface morphologies of neat PI and its composites were examined by scanning electron microscopy and the wear mechanisms were discussed. Moreover, all filled polyimides have superior tribological characteristics to unfilled polyimides. The optimum wear reduction was obtained when the content of carbon fiber is 20 vol %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Preparation and properties of T300 carbon fiber‐reinforced thermoplastic polyimide composites

AbstractIn this study, a series of T300 carbon fiber‐reinforced polyimide (CFRPI) composites were prepared by laminating premolding polyimide (PI) films with unidirectional carbon fiber (CF) layers. On the basis of PI systems design, the effect of CF volume fraction, processing conditions, and PI molecular structure on the properties of CFRPI composites was studied in detail. In addition, two kinds of nano‐particles, including carbon nano‐tube (CNT) and SiO2 were filled into the premolding PI films with different concentrations. And the effect of nano‐particles on the properties of CFRPI composites was also investigated. The surface characteristic of T300 CF was measured by X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The properties of premolding PI film and CFRPI composites were measured by dynamic mechanical analysis (DMTA), SANS testing machine, scanning electron microscopy (SEM), and so forth. These experimental results showed that the properties of CFRPI composites were mainly affected by the premolding PI film and molding condition. The change of CF volume fraction from 55% to 65% took little effect on the mechanical properties of CFRPI composites. In addition, the incorporation of nano‐particle SiO2 could further improve the properties of CFRPI composites, but CNT hardly improved the properties of CFRPI composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 646–654, 2006

Short Carbon Fiber-Reinforced PMR Polyimide Composites with Improved Thermo-oxidative and Hygrothermal Stabilities

A series of short carbon fiber-reinforced polyimide composites (SCF/PI) with different SCF loadings was prepared by thermal curing of B-staged molding powders, which were obtained by impregnating short carbon fibers with PMR monomer solution in ethyl alcohol, followed by thermally baking up to 220°C. The B-staged molding powders possess good melt-flowing characteristics and processing properties. Experimental results demonstrated that the fully-cured SCF/PI composites exhibited high thermal stability with the glass transition temperatures determined by dynamic mechanical analysis (DMA) of 412-432°C and the decomposition temperatures at 5% of weight loss in the range 497-512°C. The SCF/PI composites also had good mechanical properties, which were affected by the SCF loading. The tensile strength and the flexural strength of SCF/PI composites increased as the SCF loadings increased and then decreased gradually. SCF-20/PI has the highest tensile strength of 101 MPa and SCF-10/PI gave the highest flexural strength of 154 MPa. The SCF/PI composites exhibited a great improvement in impact toughness in comparison with PMR-15. Despite the impact strength of SCF/PI being slightly decreased as the SCF loading was increased, it was still within the range of 15-23 J cm~2.Furthermore, SCF/PI composites exhibited excellent thermal-oxidative and hygrothermal stabilities. The SCF/PI composites showed a weight loss of less than 6% after isothermal aging for 500 h at 320°Cinair. There was no significant difference in thermogravimetric analysis (TGA) and DMA curves for SCF-20/PI after hygrothermal treatment at 120°C under 2 atm for 50 h