Carbon Fiber-reinforced Polyimide 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.

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.

Study on influence of heat treatment on interfacial adhesion of CF/PI composites

In order to improve the service performance of carbon fiber reinforced polyimide (CF/PI) composites, the interfacial adhesion and failure mechanism were investigated via micro-bond test. Composites were formed by carbon fiber (sized and unsized TG800) and PI matrix (KH308 and KH500), and various heat treatments were designed and performed on each system. The results of CF/PI composites after high-temperature treatments showed that the interfacial shear strength (IFSS) always increased and then decreased with the increasing temperate due to the change of failure modes, and the performance retention rate of composites formed by KH500 was much higher under the same treatment. While the IFSS results of composites formed by KH308 and KH500 after long-time treatments were completely different, reflecting the proper service temperature of CF/PI composites. Besides, although it would decompose during curing process, the sizing agents still increased the active functionality on fiber surfaces, contributing to the interfacial adhesion of CF/PI composites at high temperature.

Study on properties influence of carbon fiber reinforced polyimide composites via surface modification using metal mesh

AbstractIn this work, carbon fiber reinforced polyimide (CF/PI) composites via surface modification using metal mesh were obtained. The interfacial adhesion performance of metal mesh and composites, mechanical properties and electrical properties of composites were characterized. The results revealed that introducing metal mesh on CF/PI composites surface obviously decreased the resistivity of composites, which was of great significance for lightning protection. For the mechanical properties, the short‐beam shear strength and flexural properties of modified composites slightly declined, and the failure mode of samples did not change significantly. From microscopic failure morphology and finite element analysis, it can be illustrated that the crack generated from edge may lead to the mechanical properties changes of metal mesh modified sample. Based on practical application condition, the performance change rule of modified composite system after thermal treatment was also reported. This study enables a surface modification thought as a promising way for the application of high temperature resistant CF/PI composite system.

Effect of Vacuum-Ultraviolet Light Irradiation on Thermal Fusion Bonding Strength of Carbon Fiber-Reinforced Polyimide Composite with Thermoplastic Polyimide Film

Effect of Vacuum-Ultraviolet Light Irradiation on Thermal Fusion Bonding Strength of Carbon Fiber-Reinforced Polyimide Composite with Thermoplastic Polyimide Film

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.

High-temperature effect on the mechanical performance of screwed CFRPI–TC4 alloy joints repaired with metal inserts

This paper seeks to study high-temperature effect on mechanical performance of screwed single-lap carbon fiber-reinforced polyimide–TC4 titanium alloy joints repaired with metal inserts. Quasi-static tension tests were conducted at room temperature (RT) and 250℃ to determine the joint strength and stiffness of repaired joints with metal inserts. Based on the experimental results, high-temperature effect on joint strength and stiffness and insert repair efficiency were analyzed and discussed. A new analytical model was established to evaluate the effect of high temperature on joint stiffness. It is concluded that (1) joint strength and stiffness for all configurations are lower at 250℃ than that at RT, showing the expected detrimental effect of high temperature on joint strength and stiffness. The reductions in joint strength and stiffness depend on the joint configuration; (2) the repair efficiencies of embedded conical nut for joint strengths of protruding and countersunk head screw joints decrease, but those for joint stiffness increase at 250℃ as against at RT. Unlike the repair efficiencies of embedded conical nut, the repair efficiency of bushing for joint strength is slightly greater, but that for joint stiffness is less at 250℃ than at RT; and (3) the developed analytical model is capable of predicting the displacement of screwed single-lap carbon fiber-reinforced polyimide–TC4 joints at RT and high temperature, and there is good agreement between the experimental data and the predicted curves.

Long-term thermal stability of carbon fibre-reinforced addition-type polyimide composite in terms of compressive strength

A previously developed carbon fibre-reinforced addition-type polyimide composite material was exposed to temperatures of 240, 270 and 300 °C in air for 3000 h to study its long-term stability in terms of its compressive strength. The in-plane shear modulus, compressive failure mode and transverse crack density were also evaluated to determine whether a degradation process induces a decrease in the compressive strength of a high-temperature polymer matrix composite having a laminated configuration of [90/0]4s. The carbon fibre-reinforced polyimide composite exhibited excellent thermal stability in terms of its compressive strength after being subjected to ageing at 240 °C for 3000 h and at 270 °C for 2000 h, with degradation becoming significant at 300 °C. The compressive strength decreased only when the surface degradation caused the 90° plies sandwiching the 0° plies to degrade severely.

Development of novel high Tg polyimide-based composites. Part II: Mechanical characterisation

In this study, the mechanical performance assessment of a newly developed carbon fibre-reinforced polyimide composite system T650/NEXIMID® MHT-R is presented. This system was subjected to a series of mechanical tests at ambient and elevated temperature (320℃) to determine basic material properties. Moreover, an additional test was conducted, using a T650/NEXIMID® MHT-R laminate in which the fibre sizing was thermally removed prior to laminate manufacturing, to investigate the effect of fibre treatment on mechanical performance. The experimental results indicated that the T650/NEXIMID® MHT-R composites along with exceptionally high Tg (360–420℃) exhibited competitive mechanical properties to other commercially available polyimide and epoxy-based systems. At elevated temperature, the fibre-dominated properties were not affected whilst the properties defined by matrix and fibre/matrix interface were degraded by approximately 20–30%. Finally, the fibre sizing removal did not affect the tensile and compressive strength, however, the shear strength obtained from short-beam shear test was deteriorated by approximately 15%.

Hygrothermal characterization of polyimide–titanium‐based fibre metal laminate

Polyimide‐based composites are currently being used on structures for both military and civilian aircraft. A major concern with these materials is the effect of long‐term exposure to service environments on their physical and mechanical properties. Hygrothermal ageing experiment was performed to understand the long‐term moisture absorption behaviour of carbon‐fibre reinforced polyimide (CF/P) and polyimide–titanium‐based fibre metal laminates (FMLs) in this work. Specimens were hygrothermal conditioned at 85°C, 95% relative humidity (RH) from 250 h to 1,000 h. Then, the moisture absorption of the specimens was determined. It was observed that the moisture absorption in the FMLs was quite slow according to the barrier function of the metal. More significantly, the mechanical properties of the CF/P and FMLs, obtained from flexure and interlaminar shear test, were affected by ageing with the reduction of flexure and interlaminar shear strength. Also, the decay mechanism of the mechanical property caused by hygrothermal ageing was further verified by means of scanning electron microscope (SEM) and dynamic mechanical analysis (DMA) techniques. POLYM. COMPOS., 39:2819–2825, 2018. © 2016 Society of Plastics Engineers

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.

Effect of different lay-ups on the microstructure, mechanical properties and neutron transmission of neutron shielding fibre metal laminates

A novel neutron shielding fibre metal laminates (NSFMLs) with different lay-ups, composed of stacking layers of AA6061 plates, neutron shielding composite and carbon fibre reinforced polyimide (CFRP), were fabricated using hot molding process in atmospheric environments. The microstructure, mechanical properties and neutron transmission of the NSFMLs were evaluated, respectively. The results indicated that the NSFMLs possessed good mechanical properties owing to the good interfacial adhesion of the components. Tensile strength and elastic modulus of the NSFMLs increased with the numbers of lay-ups, while the elongation to fracture exhibited obvious declining tendency. Flexural strength and modulus of the NSFMLs were improved obviously with the increasing of stacking layers. Neutron transmission of the NSFMLs decreased obviously with increasing the number of lay-ups, owing to the increase of 10B areal density. Besides, the effect of carbon fibres on the neutron shielding performance of the NSFMLs was also taken into consideration.

The tribological properties of carbon fiber reinforced polyimide matrix composites under distilled water condition

Purpose– The purpose of this paper is to prepare carbon fiber-reinforced polyimide matrix composites and to investigate the single role of carbon fiber in polyimide composites on tribological performance under distilled water condition.Design/methodology/approach– Three carbon fiber-reinforced polyimide matrix composites were fabricated by using a hot press molding technique. The tribological behaviors of carbon fiber-reinforced polyimide matrix composites sliding against steel ball were evaluated with a ball-on-disk tribotester under distilled water condition. Meanwhile, the effect of different length of carbon fiber on the wear resistance of polyimide matrix composites was investigated during the sliding process.Findings– The friction coefficients and specific wear rates of polyimide composites containing 100 μm carbon fibers were lower than those of other specimens. The wear mechanism of carbon fiber-reinforced composites was delamination under distilled water condition. The interfacial combination between the carbon fiber and matrix became worse with the increase of length of carbon fiber.Originality/value– This paper reported the effect of the different length of carbon fiber on polyimide matrix composites to prepare mechanical parts in mining industrial fields.

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.

Enhancement and wettability of self-assembled GO sheets as interfacial layers of CF/PI composites

The self-assembled GO interlayers are easily fabricated by a dip coating process. Carbon fiber reinforced polyimide (CF/PI) composites are prepared by the infiltration process and compression moulding. The GO interfacial properties with different cycles are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and static contact angle measurement. Furthermore, the mechanical properties are measured by the three point flexural test. And the fracture modes are determined by the SEM morphologies of the fracture surfaces.

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.

Mass Gain of Carbon Fiber Reinforced Polyimide (CFRP) by Dipping in Hot Distilled Water

Influence of isothermal dipping in hot distilled water for 200 ks on the mass gain of carbon fiber reinforced polyimide (CFRP) was investigated. Dipping in distilled water raised the mass gain. Based on the kinetics equation, both reaction index (n) and kinetic constant (k) were obtained. Since the n value is approximately 0.6 from 333 to 373 K, the reaction mode was independent on the absorption temperature. Based on the results and discussion, the water absorption was probably the directional mass transport through the fiber/polyimide cylindrical interface. On the other hand, Arrhenius linear relationship between logarithmic k (log k) and reciprocal dipping temperature (1/T) was obtained. The apparent activation energy estimated by the slope of water absorption in the CFRP was approximately equal to the activation energy of self-diffusion coefficient of water molecule. Mass gain of CFRP (CF/PI) dipped in distilled water for 100 ks at 373 K probably enhanced the molecules’ density induced by water molecules’ intrusion among polyimide polymers, resulting in enhancement of (dσ/de)max and fracture stress. On the other hand, the mass gain by dipping for 200 ks at 373 K enriched the water concentration in polyimide matrix. Thus, it was assumed to enhance the intermolecular distance of polyimide polymers and then to reduce the intermolecular force among polyimide polymers, resulting in a drop of (dσ/de)max of CFRP dipped for 200 ks. On the other hand, the dipping for 200 ks probably raised the intermolecular force between water molecules and polyimide polymers, resulting in remarkable enhancements of the fracture strain, fracture energy and impact value of the CFRP.

The Addition of Polyethylene-Polyamine Surface Treated Carbon Nanotube on the Interfacial Adhesion of Carbon Fiber-Reinforced Polyimide Composite

Carbon fiber reinforced polyimide (CF/PI) composites have been filled with polyethylene-polyamine-treated carbon nanotube to enhance the adhesion. According to the modification, the interlaminar shear strength (ILSS) of composites has been greatly improved. Dynamic wetting method, XPS and SEM are used to examine the microscopic properties of resultant composites. The enhanced ILSS is attributed to the CNT interlock, which improves the wetting between carbon fibers and resins.

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.