Search Results (45)

Jointing is inevitable for CFRTP (carbon fiber reinforced thermoplastic) component applications in the automotive industry. In this study, commonly used jointing methods were applied to fasten CFRTP components. Three types of jointing methods. Ultrasonic welding, bolted joints, and adhesive joining, and three types of CFRTP materials, conventional cross-ply, ultra-thin prepreg cross-ply, and sheet molding compounds, were selected. The influence of the jointing methods on mechanical properties and damage patterns under bending load has been investigated. The finite element models were developed to predict the hazardous area and structural stiffness of jointed structures; the simulation results showed good agreement with experimental ones. The results indicate that the ultrasonic welding could reach similar bending stiffness compared to adhesive joining, whereas the stiffness of bolt jointed structures is relatively lower due to the contact separation induced by the bending deformation. Overall, the finite element model results correlated well with the experimental data. Full article

High-performance discontinuous carbon-fiber-reinforced thermoplastics (CFRTPs) offer promising manufacturing flexibility and recyclability for advanced composite applications. However, their mechanical performance and reliability strongly depend on the internal fiber architecture, which is largely determined by the molding process. In this study, three distinct compression molding approaches—CFRTP sheet molding compounds (SMCs), bulk molding compounds (BMCs), and free-edge molding compounds (FMCs)—were systematically evaluated to investigate how processing parameters affect fiber orientation, tape deformation, and impregnation quality. X-ray micro-computed tomography (XCT) was employed to visualize and quantify the internal structures of each material, focusing on the visualization and quantification of in-plane and out-of-plane fiber alignment and other internal structure features. The results indicate that CFRTP-SMC retains largely intact tape layers and achieves better impregnation, leading to more uniform and predictable internal geometry. Although CFRTP-BMC exhibits greater tape deformation and splitting due to increased flow, its simpler molding process and better tolerance for tape shape distortion suggest potential advantages for recycled applications. In contrast, CFRTP-FMC shows significant tape fragmentation and poor impregnation, particularly near free edges. These findings underscore the critical role of a controlled molding process in achieving a consistent internal structure for these materials for the first time. This study highlights the utility of advanced XCT methods for optimizing process design and advancing the use of high-performance discontinuous CFRTP in industry. Full article

Although fiber–matrix interfacial strengths, which affect the mechanical properties of fiber-reinforced plastics (FRPs), are considered to be determined by complex factors, few studies have systematically evaluated the relationship between the matrix properties and the fiber–matrix interfacial shear strength. In this study, the properties of various thermoplastics were measured, and the matrix tightening stress that constricts the fiber was simulated using finite element method (FEM) analysis. The relationships between the fiber–matrix interfacial shear strength and the matrix properties were clarified. The mechanical properties of carbon fiber reinforced thermoplastic (CFRTP) laminates were also evaluated, and the relationships between the fiber–matrix interfacial shear strength and the mechanical properties of CFRTP laminates were examined. The fiber–matrix interfacial shear strength showed a positive correlation with the matrix tightening stress tightening the fiber in the radial direction, as well as with matrix density, tensile strength, modulus, and melting temperature, while a negative correlation was found with the coefficient of linear expansion of the matrix. A higher fiber–matrix interfacial shear strength can be achieved by using a matrix with higher density, even without direct evaluation of the fiber–matrix interfacial strength, as the fiber–matrix interfacial shear strength showed a strong positive correlation with matrix density. Furthermore, the mechanical properties of CFRTP laminates were enhanced when matrices with higher fiber–matrix interfacial shear strength were used. Full article

The thermal protection system of a re-entry vehicle requires a high-heat-resistant heat shield to protect the spacecraft. Most of the ablative materials developed so far have high heat resistance but have technical issues such as long production times. In this study, we propose a new ablative material (LATS/PEEK) consisting of PEEK and carbon felt as a material that can solve these problems. PEEK has excellent properties such as a short production time and its ability to be produced using 3D printer technology. In addition, PEEK can be molded with a variety of fusion bonding methods, so it is possible to mold the heat shield and structural components as a single structure. However, heating tests conducted in previous research have confirmed the expansion phenomenon of CF/PEEK produced by 3D printers. The expansion of the ablative material is undesirable because it changes the aerodynamic characteristics during re-entry flight. Therefore, the purpose of this research is to clarify the mechanism of the expansion phenomenon of the ablative material based on PEEK resin. Therefore, we conducted thermal gravimetric analysis (TGA) and thermomechanical analysis (TMA) and concluded that the expansion phenomenon during the heating test was caused by the pressure increase inside the ablative material due to pyrolysis gas. Based on this mechanism, we developed a new 3D LATS/PEEK with a structure that can actively release pyrolysis gas, and we conducted a heating test using an arc-heating wind tunnel. As a result, it was found that 3D LATS/PEEK had less expansion and deformation during the heating test than CF/PEEK manufactured using a 3D printer. Full article

Ultrasonic welding (USW) is considered one of the most suitable methods to join semi-crystalline carbon fiber-reinforced thermoplastics (CFRTPs). The degree of crystallinity (DoC) of the semi-crystalline resin will affect the ultrasonic welding process by affecting the mechanical properties of the base material. In addition, ultrasonic welding parameters will affect the joint performance by affecting the DoC of the welded material at the welding interface. This paper investigates the effect of DoC of carbon fiber-reinforced PA6 (CF/PA6) base material and welded material on its ultrasonically welded joints’ performance. Distinct pre-welding heat treatments are conducted on the base material before welding. The DoC is calculated by DSC, while the crystalline phases (α and γ phases) and crystallize size are determined using XRD. The results demonstrate that the heat treatment process of heating temperature of 180 °C and cooling with an oven (180-O) could increase the DoC of CF/PA6 from 27.2% to 33% and the ratio of α/γ from 0.38 to 0.75. The joint strength of 180-O sheets reached 17.7 MPa, which is 26.7% higher than that of the as-received sheets. The DoC of the welded material at the welding interface obtained with different combinations of welding parameters is characterized. Higher welding force and amplitude result in faster cooling rate at the welding interface and more effective strain-induced crystallization, leading to higher DoC of the welding interface. Full article

Steel pipeline systems carry about three-quarters of the world’s oil and gas. Such pipelines need to be coated to prevent corrosion and erosion. An alternative to the current epoxy-based coating, a multi-layered composite coating is developed in this research. The composite coatings were made from carbon fiber-reinforced thermoplastic polymer (CFRTP) material. Uniaxial carbon fiber CF/PPS prepreg tape was utilized, where the PPS (polyphenylene sulfide) is employed as a thermoplastic (TP) matrix. Compression molding was used to manufacture three flat panels, each consisting of seven plies: UD (Unidirectional), Biaxial, and Off-axis. Samples of carbon steel were coated with multi-layered composites. The physical, mechanical, and corrosion-resistant properties of steel-composite coated samples were evaluated. A better and more promising lap-shear strength of about 58 MPa was demonstrated. When compared to the Biaxial and Off-axis samples, the UD assembly had the maximum flexural strength (420 MPa); however, the Biaxial coating has the highest corrosion resistance (445 kΩ·cm²) when compared to the Off-axis and UD coatings. Full article

Continuously reinforced thermoplastic composites are widely used in structural applications due to their toughness, light weight, and shorter process cycle. Moreover, they provide flexibility in design and material selection. Unlike thermoset composites, continuous fiber content to maximize mechanical properties in thermoplastic composites has not been well investigated. In this paper, three thermoplastic systems are investigated to study the optimum content of continuous fiber reinforcement. These systems include carbon fiber/polyphenylene sulfide (PPS), glass fiber/PPS, and glass fiber/high-density polyethylene (HDPE). Tapes were made at several fiber contents, and samples were compression molded and tested using thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile, 3-point flexure, and short-beam shear tests. Results revealed that higher fiber content led to an increase in the glass transition and melt transition temperatures of the polymer. Some mechanical properties increased with fiber content and then began to decrease upon further addition of fibers, while other properties, such as ductility and interfacial bond strength, decreased with more reinforcement. Furthermore, the optimum fiber contents to maximize mechanical properties are different for different properties and different materials. Full article

Diverse industries are witnessing an increase in demand for hybrid structures of metals and carbon-fiber-reinforced thermoplastic composites (CFRTPs). Welding is an essential technique in the manufacture of metal–CFRTP hybrid structures. However, achieving high-strength metal–CFRTP welded joints faces serious challenges due to the considerable disparities in material characteristics. As an effective method to strengthen metal–CFRTP joints, surface texturing on metal is gaining significant attention. This study introduces an emerging surface texturing approach, electrochemical jet machining (EJM) using a film electrolyte jet, for enhancing the performance of AA6061-CF/PA66 hot-pressure-welded (HPW) joints. Parametric effects on surface morphology and roughness in the EJM of AA6061 are investigated. The results show that a rough surface with multiscale pores can be generated on AA6061 by EJM, and that surface morphology can be modulated by adjusting the applied current density and jet translational speed. Subsequently, the effects of different EJM-textured surface morphologies on the performance of HPW joints are examined. Surface textures created by EJM are demonstrated to significantly enhance the mechanical interlocking effect at the bonding interface between AA6061 and CF/PA66, resulting in a substantial increase in joint strength. The maximum joint strength attained in the present work with EJM texturing is raised by 45.29% compared to the joints without surface texturing. Additionally, the joint strength slightly improves as the roughness of EJM-textured surfaces rises, with the exception of rough surfaces that are textured with a combination of low current density and rapid translational speed. Overall, these findings suggest that EJM texturing using a film jet prior to welding is a potential approach for the manufacture of high-performance metal–CFRTP hybrid structures. Full article

Traditional metal–plastic dissimilar welding methods directly heat the metal workpiece, which may cause potential thermal damage to the metal workpiece. Ultrasonic extruded weld-riveting (UEWR) is a relatively new method for dissimilar joining of carbon fiber-reinforced thermoplastic (CFRTP) and metal. In this method, the CFRTP workpiece is melted using the ultrasonic effect and is squeezed into prefabricated holes in the metal workpiece to form a rivet structure. In this method, the metal workpiece is not directly heated, and potential high-temperature losses can be avoided. This paper investigates the process characterizations of UERW of AZ31B magnesium alloy to carbon fiber-reinforced PA66. The process parameters are optimized by the Taguchi method. The joint formation process is analyzed based on the fiber distribution in the cross-sections of joints. The effects of welding parameters on the joint microstructure and fracture surface morphology are discussed. The results show that a stepped amplitude strategy (40 μm amplitude in the first stage and 56 μm amplitude in the second stage) could balance the joint strength and joint appearance. Insufficient (welding energy < 2600 J or amplitude-A < 50%) or excessive (welding energy > 2800 J or amplitude-A > 50%) welding parameters lead to the formation of porous defects. Three fracture modes are identified according to the fracture surface analysis. The maximum tensile shear strength of joints at the optimal parameters is about 56.5 ± 6.2 MPa. Full article

Continuous fiber reinforced thermoplastics (cFRTP) are one of the most promising lightweight materials. For their use in structural components, reproducible and comparable material values have to be evaluated, especially at high strain rates. Due to their high stiffness and outstanding strength properties, the evaluation of the material behavior at high strain rates is complex. In the presented work, a new tensile specimen geometry for strain rate testing is virtually optimized using a metamodel approach with an artificial neural network. The final specimen design is experimentally validated and compared with rectangular specimen results for a carbon fiber reinforced polycarbonate (CF-PC). The optimized specimen geometry leads to 100% valid test results in experimental validation of cross-ply laminates and reaches 9% higher tensile strength values than the rectangle geometry with applied end tabs at a strain rate of 40 s⁻¹. Through the optimization, comparable material parameters can be efficiently generated for a successful cFRTP strain rate characterization. Full article

In this study, we focus on 3D-printed PEEK/CFRTP (Carbon-Fiber-Reinforced Thermoplastic) and PEEK (Polyether Ether Ketone) materials as new space materials. In space, there are intense ultraviolet (UV) rays that are weakened by the atmosphere on Earth, so it is essential to understand the degradation of materials due to UV rays in advance. Therefore, we developed a materials science experiment called the Material Mission, which will be carried out on board Ten-Koh 2. This mission measures the coefficient of thermal expansion (CTE) of the CFRTP samples and the PEEK samples in LEO without recovery. So, we developed a thermal expansion observation system to be installed on the Ten-Koh 2 satellite. In addition, UV irradiation tests simulating the UV environment in LEO were conducted as ground tests. From the results of the ground tests, it was possible to determine in advance the degree of degradation of each material in the UV environment, even up to 100 ESD. By utilizing these results in mission operations, more meaningful measurement results can be obtained, and this mission development can contribute greatly to developing new space materials in the future. Full article

Lightweight component design is effectively achievable through sandwich structures; many past research studies in the aerospace and racing sectors (since the 1920s) have proven it. To extend their application into the automotive and other transport industries, manufacturing cycle times must be reduced. This can be achieved by sandwich materials made of continuous fibre-reinforced thermoplastic (CFRTP) cover layers and thermoplastic honeycomb cores. To widen the application of flat thermoplastic-based sandwich panels into complex parts, a novel forming technology was developed by the Fraunhofer Institute of Microstructure of Materials and Systems (IMWS). Manufacturing defects like wrinkling and surface waviness should be minimised to achieve high reproducibility of the sandwich components. Studying different manufacturing parameters and their influence on the final part is complex and challenging to analyse through experiments, as it is time-consuming. Therefore, a finite element (FE) modelling approach is implemented to reduce such efforts. Initially, a thermoforming model is developed and validated with experimental results to check its reliability. Further, different simulations are performed to optimise the novel sandwich-forming process. In this study, a thermoplastic sandwich made of polypropylene (PP) honeycomb core and polypropylene glass fibre (PP/GF) cross-ply as cover layers was used, and its numerical model was executed in LS-DYNA software release R11.2.1. Full article

In the press and injection hybrid molded parts of fiber-reinforced thermoplastics (FRTPs), failure at the interface between the surface material (the outer shell) and the ribs (the injection part) or that at the injection part has become an issue. Adding a resin layer to the rib roots at the same time that the ribs are molded through injection has been proposed, which may increase the mechanical properties and reduce the material cost. To prevent failure at the injection part, the use of fiber-reinforced resin as an injection material has been suggested. This approach contributes to a higher bond strength by lowering the molding shrinkage rate. In this study, the hat-shaped parts of carbon fiber-reinforced thermoplastics (CFRTPs) with fiber-reinforced and neat resin layers at the rib root were fabricated through press and injection hybrid molding, and their mechanical properties were evaluated through three-point bending tests. The effects of the resin layer at the rib root and the existence or nonexistence of fiber reinforcement on the mechanical properties, as well as the relationship between the material cost and the mechanical properties, were clarified through an experiment and FEM analysis. The bond strength was also evaluated through tensile tests that were undertaken at the rib root. Molded parts with neat PA6 and glass fiber-reinforced PA6 resin layers at the rib roots showed higher bond strength than those without resin layers. In a three-point bending test of a CFRTP hat-shaped part with a resin layer at the rib roots, the use of a 1 mm thick CFRTP laminate for the outer shell and glass fiber-reinforced PA6 resin as the injection material showed the same stiffness as a part that used a 2 mm thick CFRTP laminate for the outer shell. FEM analysis showed that the resin layer prevented the concentration of strain at the rib roots, and the model that used a 1 mm thick CFRTP laminate for the outer shell and glass fiber-reinforced PA6 resin as the injection material showed the best specific stiffness in this study. By adding a resin layer to the rib roots, the fabrication of molded parts with excellent specific stiffness was enabled at a small increase in cost. Full article

Carbon fiber-reinforced thermoplastics (CFRTPs) have attracted attention in aerospace because of their superior specific strength and stiffness. It can be assembled by adhesive bonding; however, the existing evaluation of bonding strength is inadequate. For example, in a single-lap shear test, the weld zone fails in a combined stress state because of the bending moment. Therefore, the strength obtained experimentally is only the apparent strength. The true bonding strength was obtained via numerical analysis by outputting the local stress state at the initiation point of failure. In this study, the apparent and true bonding strengths were compared with respect to three types of strength evaluation tests to comprehensively evaluate bonding strength. Consequently, the single-lap shear test underestimates the apparent bonding strength by less than 14% of the true bonding strength. This indicates that care should be taken when determining the adhesion properties for use in numerical analyses based on experimental results. We also discussed the thickness dependence of the adhesive on the stress state and found that the developed shear test by compression reduced the discrepancy between apparent and true strength compared with the single-lap shear test and reduced the thickness dependence compared with the flatwise tensile test. Full article

Recently, hybrid injection molding—a type of overmolding technology in which a short carbon fiber-reinforced thermoplastic is injection molded over a compression-molded carbon fiber-reinforced thermoplastic (CFRTP) sheet—has been introduced. A heat-and-cool hybrid injection molding technique has also been introduced for practical use. The technique yields high-quality molded products. This is achieved through the heating of the mold cavity surface to a temperature higher than the melting point of the base polymer impregnated into the carbon fiber fabric. However, few experimental analyses of the molding phenomena in heat-and-cool hybrid injection molding have been reported. In particular, the effect of the processing conditions on the transfer of the mold cavity surface shape to the CFRTP sheet has not been clarified in detail. Therefore, it has been impossible to take extensive measures when defects are generated in molded products. In this study, a mold is designed and fabricated for use with far-infrared radiation heating, a variotherm technology that is suitable for the experimental analysis of the heat-and-cool hybrid injection molding phenomenon. In particular, a mold is designed and fabricated to continuously perform the following three processes using only an injection molding machine: (1) the radiation heating of both the CFRTP sheet and the mold cavity surface using a far-infrared radiation heater, (2) the compression molding of the CFRTP sheet, and (3) the injection molding of the melt. The effects of the heating conditions of the mold and the injection molding process conditions on the appearance characteristics of the molded products are clarified using this mold and a far-infrared radiation heater. Full article