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With the high precision requirements and the trend of large-scale composite parts, the development of composite molds is imminent. The short carbon fiber (SCF) composite mold is mainly prepared by the technological process flow of composite sheet injection, the bonding of composite plates, and machining. However, the current process optimization method has not matured adequately, and there are still many shortcomings, for example, low precision and high cost. In this paper, the optimization method of SCF/polyetherimide (PEI) composite molds is proposed. Many experiments have been conducted, and the results show that the coefficient of thermal expansion of composite samples can be effectively reduced and the mechanical properties can be improved by optimizing the SCF weight ratio and carbon fiber length. The bonding strength of composite joints in a high-temperature environment can be improved by optimizing the bonding process parameters and modification by carbon nanotubes. Based on the above optimization method, the SCF/PEI composite mold is prepared, and the C-shaped beam composite part is fabricated by using this mold. Compared with the part made by aluminum mold, the shape accuracy of the C-shaped beam composite part is proven high through digital measurement technology. [ABSTRACT FROM AUTHOR]

The inherent defects of the layer‐by‐layer manufacturing process limit the mechanical performance of 3D‐printed composite parts. This paper explores a process optimization method for continuous fiber composites 3D printing to improve the mechanical performance of 3D‐printed CF/PA6 (Carbon Fiber/Nylon 6) parts. First, the effects of printing temperature, printing speed, layer thickness, and side step on the mechanical performance of 3D‐printed CF/PA6 were studied by conducting variable parameter printing experiments. All optimal printing parameters for CF/PA6 were obtained, and their impact mechanisms were analyzed. Second, the coupling effect of temperature and pressure of post‐processing reduced the internal voids of 3D‐printed CF/PA6 and improved its mechanical properties. The influence mechanism of the coupling effect of temperature and pressure was summarized, and the optimal post‐processing parameters applicable to CF/PA6 were obtained. Based on the above process optimization, the fiber volume content of the printed CF/PA6 reached 41.05%, and the bending strength and elastic modulus reached 651.54 MPa and 79.08 GPa, which were 209.05% and 179.53% higher than those before optimization. Moreover, the tensile strength and elastic modulus reached 730 MPa and 29.23GPa, which were 98.10% and 81.10% higher than those before optimization. The experimental results give a positive validation of the effectiveness and feasibility of the proposed methodology. Highlights: The effects of printing temperature, printing speed, layer thickness, and side step on the mechanical properties of 3D‐printed CF/PA6 were investigated. The optimal printing parameters applicable to CF/PA6 were obtained and their influence mechanisms were analyzed.The effects of the heat press processing method on the internal voids and mechanical properties of 3D‐printed CF/PA6 were investigated, and the optimal post‐processing parameters applicable to CF/PA6 were obtained.The study resulted in optimal printing parameters and post‐processing parameters for 3D printing CF/PA6, which greatly enhanced its tensile and flexural strength and modulus. [ABSTRACT FROM AUTHOR]

Continuous carbon fiber reinforced polymer composite 3D printing has drawn more attention due to its ability to manufacture composite structures with complex shapes. The surface treatment of CF is necessary to improve the combination between carbon fiber (CF) and matrix. In this work, polyurethane with nano‐SiO2 (PU/SiO2) was used to size CF to enhance the compatibility of CF and nylon 6 (PA6). The chemistry and morphology of the CF were characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The interface strength between CF and PA6 was tested by the fiber pull‐out test, and eventually obtained optimized concertation of PU/SiO2 sizing agents (with 25 wt% PU and 0.4 wt% nano‐SiO2). The results show that compared with untreated CF, the interfacial shear strength (IFSS) of CF and PA6 after sizing increased by 316.93%. In addition, several CF/PA6 composite specimens printed by a homemade composite 3D printer were used to do mechanical tests. The results show that the flexural strength increased by 33.87%, the tensile strength increased by 20.75%, and the interlaminar shear strength (ILSS) increased by 66.54%. [ABSTRACT FROM AUTHOR]

In this study, a method for fabricating actuators made of various silicone materials is proposed to improve the flexural performance of soft-body actuators. Specifically, the redundant deformation part of the soft actuator was replaced with a material with higher hardness to limit the redundant deformation of the soft actuator. Materials with lower hardness were used to produce the main deformation part of the soft actuator, so that the soft body actuator could perform greater bending under the same air pressure and create a greater bending force. In addition, the fabricated actuator was divided into three regions in this study: the periphery of the chamber, the chamber wall (the main curved part), and the bottom surface of the actuator. The impact on the overall performance of soft-body actuators when using silicone materials with different hardness in these three regions was explored in this study. According to the idea of the multi-hardness silicone structure, an actuator with seven chambers was fabricated, and the performance of the actuator was improved by 90.72% compared with the uniform material actuator. [ABSTRACT FROM AUTHOR]

Background: When performing the spatial large-scale measurements, the measurement accuracy of laser tracker would decreased with the increase of the measurement distances due to the refraction difference of most optical digital measurement devices. Therefore, this paper proposed a method based on photogrammetry system to improve the large-scale measurement accuracy of the laser tracker. Purpose: The purpose of this method is to improve the large-scale measurement accuracy of the laser tracker by considering the advantages of photogrammetry system such as high measurement accuracy and good portability. Methods: The measurement data from the photogrammetry system would be used as a reference to do correction on measurement results from laser tracker. The coordinate correction method based on Rodrigues' rotation formula has been discussed. The measurement accuracy of the long-distance point of laser tracker can be significantly improved through the coordinate correction method. Conclusion: Based on the advantages of using photogrammetry system, the proposed method can achieve higher accuracy when measuring the common points at a closer distance than the laser tracker can do when measuring objects far away from instrument. The feasibility of the proposed method has been demonstrated by experiment. [ABSTRACT FROM AUTHOR]

This study was to solve the mandrel demolding problem after curing the composite component with complex structure. In this paper, a reusable thermoplastic mandrel with heating softening characteristics was developed by resin transfer molding (RTM). The glass transition temperature (Tg), surface roughness, and reusability of the mandrel, as well as the shape, surface roughness, thickness uniformity, and internal quality of the formed structure, were tested. The result showed that the Tg of the mandrel was between 80 and 90 °C and the surface roughness was less than Ra 0.5 μm. Additionally, the mandrel can be recycled and can still maintain a good shape after 20 times of deformation. By using this method, the demolding process can be realized by heating and softening the mandrel. The profile error of the formed structure was within 0.5 mm, the surface roughness was less than Ra 0.5 μm, the thickness error was within 0.2 mm, and the average porosity of the upper and lower halves of composite parts was 0.72% and 0.61%. All those data showed that the formed part was in good shape and of good quality. The thermoplastic mandrel can solve the demolding problem of composite materials with complex shapes. [ABSTRACT FROM AUTHOR]

Laser tracker has been used in a diverse range of applications due to its high accuracy and efficient, specifically as measuring the coordinates of points or scanning shape of objects. In real applications, we often need to measure common points on multi-stations by using this technology if objects are large scale. To ensure every common point within the range of laser tracker, common points are usually placed far from the laser tracker. However, the long distance between common points and laser tracker will decrease the accuracy of the result. In this research, we proposed a new method where photogrammetry and laser tracker are integrally used to measure common points to reduce measurement error. With the help of photogrammetry, we first constructed the geometric constraints of common points. Then, by using graphic correction method, the coordinates of common points on laser tracker will be corrected. Both of the theoretical and experimental study results indicated the great success of improving the measurement accuracy of laser tracker. We consider that this method we reported can highly increase the accuracy of measurement on laser tracker station-transfer. [ABSTRACT FROM AUTHOR]