Search

Carbon fiber-reinforced polymer composites employed in practical aerospace applications are subjected to harsh temperature changes and preloads (PLs) simultaneously. Thus, it is important to analyze the mechanical behavior of carbon fiber/polyether-ketone-ketone (CF/PEKK) composites under such conditions. Therefore, this study first performed bending tests on CF/PEEK samples at room temperature (RT), 80[Formula: see text]C, and 120[Formula: see text]C. Subsequently, bending tests were performed on CF/PEEK samples preloaded with 30%, 50%, and 70% of the ultimate load for 24 h and 72 h. Finally, bending tests were conducted on CF/PEKK samples subjected to both temperature and PL variations. The results show that as temperature increased from RT to 120[Formula: see text]C, the strain values increased, but the modulus ([Formula: see text]) and strength ([Formula: see text]) decreased. As PL increased, the flexural stress, [Formula: see text], and strain ([Formula: see text]) decreased. The samples preloaded with 30% of the ultimate load at 80[Formula: see text]C had the highest [Formula: see text], [Formula: see text], and [Formula: see text] values. However, the [Formula: see text], [Formula: see text], and [Formula: see text] values at 120[Formula: see text]C were only slightly lower than those at 80[Formula: see text]C. This proves that preloaded CF/PEKK composites maintain their high strength, toughness, and plastic behavior at high temperatures, and thus, they are suitable for aerospace applications.

A seawater electrolyzer solution has high alkalinity owing to the presence of scale-like hydroxide compounds, Ca(OH)2, and Mg(OH)2 generated from a dimensionally stable anode during electrolysis. This study proposes four different types of composite materials to replace the existing ballast piping materials that are vulnerable to high alkalinity. To this end, composite specimens were prepared and immersed in an NaOH solution for 720 h. Furthermore, their suitability as ballast pipe materials was confirmed through a physical property analysis of the immersed specimens. The results show that all four types of composite specimens deteriorated, but they had different interfacial bonding mechanisms. For specimens with low interfacial bond strength between fibers and resins, the deterioration initiated and propagated from the surface and the internal penetration of the NaOH solution occurred rapidly, resulting in the rapid deterioration of their physical properties. The mechanisms of good and bad interfacial bonding between fibers and resins were determined based on the interfacial bonding force. Thus, this study will help understand the deterioration mechanisms of composite materials immersed in chemical solutions such as NaOH or acid in the future.

Because particles that accumulate without movement can lead to a deposition gradient, the formation of a stable suspension is essential for the electrophoretic dispersion (EPD) process. The hydrophobic properties of Halloysite nanotubes (HNTs) were easily dispersed in many nonpolar polymers without further deformation steps. However, the uniform dispersion of HNTs in aqueous solutions is a pre-EPD process task. The zeta potential controls the main parameters of EPD processes, such as the density of deposits, particle orientation and velocity, and repulsive interactions between particles, which determine the stability of the suspension. In this study, the solution stability range for the addition of nanoparticles was measured and the optimal dispersion range was determined. In addition, an HNT-reinforced composite material was created by determining the optimal dispersion stability range of HNT, and the impact strength and fracture mechanism of the interface were analyzed. The solution stability and dispersion were the best between pH 6.6 and 6.8, and the highest impact strength was confirmed at 0.7 wt%. The HNT confirmed the interfacial dispersion of the EPD-fibers using scanning electron microscopy and dispersive X-ray spectroscopy (SEM-EDS).

In this study, the Liu–Murakami (LM) creep damage-coupled model was considered to evaluate the creep properties of martensitic stainless steel. The degree of creep damage was examined at two temperatures (565 ℃ and 593 ℃) to assess mechanically and thermally activated processes. A series of high applied stresses (applied stress/ultimate strength > 0.5) was considered for accelerated creep loadings. A full set of creep constants was determined by combining the Norton and LM models. Constitutive equations were used to quantitatively estimate experimental creep curves. The variation in creep constants was discussed based on stress sensitivity, such as stress triaxiality and applied stress, depending on the power of stress. The creep strain–time curves were successfully estimated. The comparison between the experimental and analytical results was in good agreement in the tertiary regime. In addition, the compensation of the two applied temperatures provides a supplementary explanation of the relationship between the ultimate strength and rupture time in terms of temperature sensitivity. The analytical results show that different applied stresses and temperatures could be compensated to characterize the creep behavior of the material. Thus, the creep strain–time and creep strain rate–certain rupture time curves were finally achieved. The analytical process in this study provides a laboratory-scale assessment of creep properties using the accelerated creep test and LM model.

This study was conducted for the purpose of deriving the optimal process conditions for the pultrusion of carbon fiber–polyester composite materials. For this purpose, the mechanical characteristics were evaluated according to fiber content, curing time, and curing temperature. Tensile strength characteristics are improved as the fiber content, curing temperature, and curing time increased. But, in a fiber content of 70% over, it does not improve due to internal defects such as delamination and voids. The effect of curing temperature and curing time was analyzed through the fracture mode. Fracture characteristics due to un-curing were observed in tensile specimens. In addition, the curing reaction of the polyester as the heating rate was confirmed through differential scanning calorimetry. Finally, the optimal process conditions for the pultrusion of carbon fiber–polyester composite materials were derived.

At present, research is actively being conducted into composite materials using natural fibers and thermoplastic resins that can serve as eco-friendly materials. However, the weak interfacial bonding shape between natural fibers and thermoplastic resins leads to low mechanical properties in the natural fiber-reinforced polymer composite. This study examined the usage of basalt fibers (BFs) and polypropylene (PP) to address this issue. Plasma surface modification (PSM) was performed on the surface of the BF to improve the interfacial bonding force between the fiber and the thermoplastic resin. Studies on monomer selection (HMDSO), plasma generation conditions (3 kV), and surface modification time (20–150 s) were conducted to determine the optimal conditions for PSM. FT-IR analysis was performed to confirm the surface modification and the fracture surface was observed after the mechanical properties were measured. The experimental results confirmed the effect of PSM on the BF resulting in about 10% improvement on the related mechanical properties.

Laminated carbon fiber-reinforced plastics (CFRPs) have been applied to complex structures in various industries owing to their excellent physical and mechanical properties. However, the use of such plastics is limited because their through-thickness failure presents an important structural vulnerability. This study aimed to develop an epoxy characterized by excellent interlaminar toughness that could be applied to filament-wound CFRP cylinders. The epoxy was modified with carbon nanotubes (CNTs) and halloysite nanotubes (HNTs), and the toughening effect of these nanomaterials on the CFRP composite was examined. The combination of CNTs and HNTs remarkably enhanced the interlaminar toughness of the epoxy and structurally improved the cohesiveness of individual nanoparticles, resulting in the partial reinforcement of the laminated structure of the CFRP. The reinforcements of the epoxy and interfacial bonding force between the epoxy and carbon fibers were also improved by the hybridization of small amounts of the CNTs and HNTs. In particular, the HNTs significantly improved the through-thickness characteristics of the CFRP by providing strong bridging effects. The interleaved CNT/HNT design developed in this work was suitable for application to hybrid-reinforced laminated CFRPs and may be considered a potential nanomaterial technology that could ensure the stable performance of CFRP-based structures against failure.

There are numerous methods for reinforcing laminate composites using nanoadditives. However, the random dispersion of nanoparticles in polymer resins leads to critical defects owing to excessive dispersion. This study investigated a method of depositing halloysite nanotubes (HNTs) on a carbon fabric surface via electrophoresis deposition (EPD) for reinforcing the through-thickness strength of carbon fiber-reinforced plastic (CFRP) composites. The voltage during the EPD process was set as 6–12 V, which is the working range for nanoparticles during EPD. In addition, CFRPs were fabricated from modified carbon fabrics using vacuum-assisted resin transfer molding. The optimum voltage was determined as 6 V. At higher voltages, the mechanical properties deteriorated owing to the distribution of HNTs and damage to the fibers. The performance of the EPD-modified CFRPs was better than that of neat CFRPs. The highest strength was observed at 0.7 wt.% HNTs and 6 V, which indicated the feasibility of the EPD process and a well-dispersed morphology. The strong interaction of HNTs with carbon fabric influences the through-thickness mechanical properties of CFRP composites.

As the IMO has strengthened its environmental regulations to increase the energy efficiency of ships, the IMO has also begun to consider operational economics such as reducing energy consumption by reducing the weights of ships and their parts. This study conducts an analysis examining the application of a ship radar mast. The applicability of the laminated composite material was analyzed through tension, shear, compressive, and tension-tension fatigue tests and the FRP fatigue limit for one million cycles by the slope of the [Formula: see text]–[Formula: see text] curve was found to be about 231 MPa. It is expected that this method can be utilized in the design stage by predicting the fatigue life of radar masts for ships through fatigue testing.

Wire-directed energy deposition (wire-DED) is used to create a shape in a layer-by-layer manner by depositing a consumable welding wire, where a welding arc is the source of heat. This technology can be used to fabricate large components with higher deposition rates compared to other 3D metal printing methods. Despite these benefits, the components of wire-DED are affected by heat distortion and residual stress. Therefore, the prediction of deformation before fabrication using wire-DED is essential for determining the range of machining for the final products. In this study, the deformation and time required were evaluated using various simulation models of wire-DED.

The chemical bonding of substrate and adhesive occurs in thermoplastic adhesive bonding, and the molecular deformation caused by the difference in chemical bonding affects the adhesive properties. Therefore, it is essential to investigate the correlation between the molecular deformation of interphase and the strength change behavior. As adhesive bonding involves the combination of two materials with different coefficients of thermal expansion, it is important to analyze the behavior at high temperatures. Therefore, to determine the effects of the molecular deformation of the interphase caused by differences in the adhesive type on the high-temperature performance when adhesive bonding is applied to thermoplastic composites, fusion and adhesive bonding were applied to carbon fiber/polyetherketoneketone thermoplastic composites. The lap shear strength test was conducted at three different temperatures to evaluate the adhesive performances. Scanning electron microscopy was used to determine the fracture mode and the molecular deformation of the interphase was analyzed by Fourier transform infrared spectroscopy. Temperature does not affect the strength of fusion bonded composites. When polyetheretherketone is used as an adhesive, the strength decreases as the temperature increases. When polyetherimide is used as an adhesive, the strength first increases at [Formula: see text]C and then decreases at [Formula: see text]C. The amount of C–O–C and C=C bond formation, diphenyl ketone group, and imide carbonyl group in the interphase followed the same trend as the strength.

A framework was presented for a fatigue failure model of fibrous composites using a multiscale approach, which uses the fatigue data of the fiber and matrix materials, respectively. Using this model, fatigue failure of fibrous composite materials and structures can be predicted from the constituent material behaviors. To that end, fiber bundles were tested under cyclic loading to determine their residual strength and stiffness. A successful completion of the model is expected to replace many fatigue tests as the configuration of the fibrous composite is varied.

The natural nanoclays and basalt fibers are attracting a considerable amount of interest due to their outstanding properties. Halloysite nanotubes (HNTs) incorporated basalt fiber reinforced polymers (BFRPs) exhibit promising potential applications in marine industries, such as offshore oil platforms and pipelines, due to their high mechanical strength and robust chemical durability. However, their damping capability, which is of great importance for large structural component applications, has not been yet thoroughly investigated. The main goal of this study is to investigate the damping property of nanoclays incorporated BFRPs, by combining the experimental patterns with the respective computational insights. Multiple-structured nanoclays were successfully synthesized by following various experimental approaches. The “stick-slip” mechanical model was implemented in order to elaborate on the energy dissipation issue, due to the development of interfacial frictional slip, whereas the experimental outcome was compared with the respective computational results in order to test the validity of our theoretical approach. Along these lines, the dynamic properties obtained by experimental analysis divulged a fair degree of agreement with the computational results. The fabrication of composites by incorporating HNTs with moderate aspect-ratio value and interfacial bonding can be considered as a quite promising solution in improving the energy dissipation performance.

Permeability is a critical parameter not only in flow simulation analysis but also in liquid composite molding process. When a liquid resin is infused into a dry preform, the impregnation is mainly characterized by the permeability. The permeability of a dry preform can be obtained through theoretical and experimental methods. In the theoretical estimation of permeability, the effects of fiber arrangement as well as fabric type and form for various types of preforms are not sufficiently reflected in the calculation. Thus, there is a gap between the theoretical and experimental permeability. Recently, experimental determination has been gaining considerable attention as a mean to obtain accurate permeability values; however, it requires a number of trials. In this study, the permeability of the Hexforce G0926 5HS (five-harness satin) carbon fabric preform is estimated using representative theoretical prediction models, the Gebart and Kozeny–Carman equations. In addition to the Kozeny–Carman permeability (using the Kozeny constant values from literature), the Kozeny constant obtained through experiments was used to obtain a modified Kozeny–Carman permeability. All three calculated permeabilities were compared and verified with the fabric manufacturer’s reference value. The results showed that the modified Kozeny–Carman permeability using the experimentally determined Kozeny constant was closest to the reference value at 57% fiber volume fraction. Further, the predicted permeability was compared with other experimental permeability values from literature over the 40%–65% range of fiber volume fraction. We found that the modified Kozeny–Carman permeability once again came closest to the literature values. Finally, an optimized fitting equation was proposed to replace the Kozeny–Carman equation for predicting the permeability of Hexforce G0926 5HS carbon fabric over the 40%–65% fiber volume fraction range.

The material with irregular atomic structures such as polymer material exhibits low thermal conductivity because of the complex structural properties. Even materials with same atomic configurations, thermal conductivity may be different based on their structural properties. It is expected that nanoparticles with conductivity will change non-conductive polymer base materials to electrical conductors, and improve the thermal conductivity even with extremely small filling amount. Nano-composite materials contain nanoparticles with a higher surface ratio which makes the higher interface percentage to the total surface of nanoparticles. Therefore, thermal resistance of the interface becomes a dominating factor determines the effective thermal conductivity in nano-composite materials. Carbon fiber has characteristic of resistance or magnetic induction and Also, Carbon nanotube (CNT) has electronic and thermal property. It can be applied for heating system. These characteristic are used as heating composite. In this research, the exothermic characteristics of Carbon fiber reinforced composite added CNT were evaluated depend on CNT length and particle size. It was found that the CNT dispersed in the resin reduces the resistance between the interfaces due to the decrease in the total resistance of the heating element due to the addition of CNTs. It is expected to improve the life and performance of the carbon fiber composite material as a result of the heating element resulting from this paper. Keywords: Carbon Nanotube (CNT), Carbon Fiber Reinforcement Plastic (CFRP), Heater, Exothermic characteristics

This study analyzed the relationship between the defect area identified through a C-scan and the void volume in CF-PEKK composite materials through the water absorption behavior to predict the void volume. The water absorption content varies with the defect area; however, the defect area identified through a C-scan and the water absorption content did not show a proportional relationship. This is because voids are distributed in the through-thickness. The results indicated that the absorption behavior could be used to predict the void volume. Irreversible absorption was found to be independent of the void volume. Further, no matrix degradation was seen with water immersion at [Formula: see text]C; however, some local swelling was seen.

The purpose of this study is to develop a lightweight design model for an 18ft leisure boat. The existing leisure boat is manufactured using glass fiber-reinforced plastics (GFRP) material and the hand lay-up process. Carbon fiber-reinforced plastics (CFRP) was applied to the new design to reduce the boat’s weight, while an automated tape laying machine was applied to the lightweight boat’s manufacturing process to increase boat manufacturing productivity. The newly designed CFRP model is 25% lighter than the existing GFRP model. It was confirmed that the newly designed lightweight hull has sufficient structural integrity compared to the existing hull through the structural integrity evaluation by the FEA.

In the present study, optimal dispersion conditions were developed to disperse nanocomposites containing halloysite nanotubes (HNTs) and unsaturated polyester (UP) resin using ultrasonic dispersion method. Due to the presence of a substantial amount of water in HNTs, their properties depend on the operating temperature when dispersing. It is, therefore, important to understand the structural changes of HNTs that occur when changing the operating temperature. HNTs heat-treated at various temperatures have different structures and mechanical/chemical properties. Therefore, in this research, HNTs were treated at two temperatures, 773.15 K and 973.15 K (500 °C and 700 °C), and the correlation between UP resin and heat-treated HNTs was studied in detail. The quantities of HNTs were 0.5 and 1 wt pct, for the 773.15 K and 973.15 K (500 °C and 700 °C) heat treatment temperatures, respectively. The contents of HNTs were restricted in order to demonstrate the aggregation phenomenon. The dispersion was carried out by ultrasonication. All structural changes including dispersion behavior were examined by TEM. The mechanical properties were assessed by impact tests. The results showed that the high impact strength of the nanocomposite containing 1 wt pct of 973.15 K (700 °C) heat-treated HNT was superior. In other words, it can be said that the rheological property of the matrix resin depended on the quantities of HNTs and the heat treatment temperature.

The failure mechanism of composites dominates the matrix, fiber and interface, and in general, the matrix corresponds to the definitive cause of damage. A filament–wound composite structure involves a notable bridging effect owing to the matrix between the layers, and particle additives are generally adopted to strengthen the matrix. However, particle additives exhibit a low performance when applied to structures, owing to the dispersibility and particle agglomeration. In this study, the strengthening performance of carbon nanotube (CNT)/epoxy interleaves was experimentally verified to facilitate their implementation in the structural design of a filament–wound cylinder structure. The burst pressure, compression, bending and interfacial bonding strength of the cylinder improved by approximately 20%, 161%, 16% and 36%, respectively, and the positioning of CNT/epoxy interleaves was a more notable influencing factor compared to the proportion of CNTs in the entire winding layer. The number of macro voids decreased inside the epoxy modified CNT. The findings demonstrated that the incorporation of CNTs through CNT/epoxy interleaves could facilitate the matrix strengthening and enhance the interfacial bonding.

This study achieved a homogeneous hierarchical distribution of non-conductive halloysite nanotubes (HNTs) on unidirectional glass fabrics using electrophoretic deposition (EPD). Silane modification was successfully applied to HNTs and glass fabrics. The HNTs and glass fabrics were covalently bonded by condensation polymerization between the carboxyl and amino groups during the EPD process. The HNT-grafted glass fabrics were fabricated into glass fiber-reinforced polymers (GFRPs) using vacuum-assisted resin transfer molding. These results demonstrate an effective enhancement in the through-thickness of HNT-grafted GFRPs. The enhanced mechanical properties of the hierarchically and covalently distributed HNTs were attributed to the excellent interfacial bonding and nanobridging of the HNTs.

While thermoplastic polymers exhibit several desirable properties, their applicability is limited by their high viscosity and extreme processing conditions. To overcome these limitations, in this study, we used the thermoforming process to produce carbon fiber/polyetherketoneketone (CF/PEKK) laminates, which were pre-made through an oven-based consolidation process using prepregs. The laminates were produced at three different heating rates ([Formula: see text]C/min, [Formula: see text]C/min and [Formula: see text]C/min). The laminates produced at the heating rate of [Formula: see text]C/min showed improved interlaminar shear strength, [Formula: see text] tensile strength, and average interlaminar fracture toughness. On the other hand, heating at rates higher than [Formula: see text]C/min increased the initiation value of the interlaminar fracture toughness ([Formula: see text] but resulted in nonuniform composites of poor quality. This is because increasing the heating rate reduced the uniformity of the heat distribution with the laminates, resulting in the polymer molecules exhibiting different binding rates and thus nonuniform cross-linking. Thus, the proposed method is a suitable one for producing high-quality thermoplastic composites.

Vacuum-assisted resin transfer molding (VaRTM) is becoming one of the most robust alternatives for autoclave processes. VaRTM, which applies the resin injection method in a vacuum environment, generally uses fiber reinforcement and a polymer matrix separately in the process. The VaRTM is mainly dominated by the characteristics of constituent materials, such as preform permeability and resin viscosity. Among them, process design with the arrangement of resin inlet/outlet locations is closely related to process defects, and inappropriate inlet/outlet layouts cause voids, etc, which has a decisive effect on quality degradation. Therefore, in this study, a highly curved and twisted spar structure was fabricated by the VaRTM, and both flow simulations using Programs for Applied Mechanics–Resin Transfer Molding software and experimental test parts built with three different inlet/outlet line conditions were performed and compared to predict and improve impregnation quality. There was good agreement between the simulation and built test specimen for the three cases that the shorter inlet and outlet length resulted in improved impregnation quality. It was verified that impregnation and inner quality could be improved through flow simulation analysis during the VaRTM process.