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The use of fiber-reinforced composites instead of metal materials as load-bearing components has become one of the effective means of weight reduction in the automotive and aerospace fields. The reusability and reusability characteristics have promoted the promotion and application of thermoplastic composites. However, the interface between multiple materials can be the weakest area of extrusion injection molding (IMAC) components, which limits the optimization and improvement of the overall performance of the composite. In order to understand the influence mechanism of different surface treatment methods on interface properties, recently, scholars from Beijing University of Aeronautics and Astronautics have adopted different surface treatment methods to ** the binding interface properties of carbon fiber (CF) and glass fiber (GF) reinforced PA6 or PA66 matrix composites commonly used in the automotive industry.
In this study, five test components were mainly designed, which were used for the cross tensile test, the three-point flexure test, the single lap shear test, the double cantilever beam (DCB) test, and the end notch bending (ENF) test, as shown in Figure 1. Typical force-displacement curves for the five test specimens are shown in Figure 2 to obtain interfacial performance metrics for surface-untreated bimaterials, including GIC, GIIC, , T, and B[Learn more about 'plastics', 'engineering plastics', 'modified plastics' and other industry knowledge, massive material super physical property tables, super material selection cases, cost reduction and efficiency improvement solutions, welcome to "plastic library network" to understand! 】。The test results show that the interface of PA6 PA66 is slightly lower than that of PA6 PA6, and the other performance indicators are the opposite. The GICs and GICs of the PA6 PA66 bimaterial joints are almost twice that of the PA6 PA6 bimaterial joints, so it can be considered that the binding interface performance of the PA6 PA66 is better than that of the PA6 PA6 material system. For IMAC components, the use of different substrates can improve the interfacial properties, especially the tensile and shear fracture properties.
Fig.1 Schematic diagram of the structure and dimensions of the five test specimens.
Fig. 2 Typical force-displacement curves for five test specimens.
As shown in Figure 3, the typical curves and peak force pairs of the DCB test of bimaterial joints under different interface treatments show that all specimens exhibit linear behavior before crack propagation. For PA6 PA66 and PA6 PA6 interfaces, both sandpaper sanding and sandblasting can improve the interface load-bearing capacity, as sanding and sandblasting increase the interface roughness and therefore improve the fracture resistance of the interface. For the PA6 PA6 bonding interface, the optimization effect of sandblasting treatment on the interface bonding strength is better than that of sandpaper sanding treatment[Learn more about 'plastics', 'engineering plastics', 'modified plastics' and other industry knowledge, massive material super physical property tables, super material selection cases, cost reduction and efficiency improvement solutions, welcome to "plastic library network" to understand! 】。With the increase of the number of meshes of sandpaper and sandblasting screen, the interfacial fracture energy of bimaterial components gradually increases, and the maximum fracture energy is about 9 of the surface untreated specimen31 times. For the PA6 PA66 interface, the effect of sandpaper sanding on fracture energy is better than that of sandblasting. The fracture energy of the composites is slightly higher than that of the uncoated composites after coating treatment before interface bonding. As shown in Figure 4, the interfacial fracture energy decreases gradually with the increase of the mesh number of sandpaper and sandblasting screens. After surface treatment, more defects are introduced to reduce the ability to resist shear stress, so the interface fracture energy decreases after surface treatment.
For bonding systems, there are typically four main failure modes: bond interface failure, cohesive failure, matrix failure, and hybrid failure, all of which are possible for the bimaterial interface studied here. When the interface has a variety of failure modes[Learn more about 'plastics', 'engineering plastics', 'modified plastics' and other industry knowledge, massive material super physical property tables, super material selection cases, cost reduction and efficiency improvement solutions, welcome to "plastic library network" to understand! The methods used to improve the performance of the interface are also more complex. Although different methods for improving interfacial properties are proposed, the internal mechanism is not clear, and improving the resistance of one failure mode may deteriorate the resistance of the system to other failure modes, so it is necessary to find the most excellent performance improvement method to ensure the safety of composite materials under complex service conditions.
Fig.3 Comparison of typical curves and peak forces of bimaterial joints under different interface treatments.
Fig.4 Comparison of typical curves and peak forces of bimaterial joints under different interface treatments.
The study was published in Composite Structures under the title "Study on the Interfacial Properties of Bi-Material Structures Manufactured by Injection Molding After Compression".
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