Abstract
Three-dimensional braided composite has a unique spatial network structure that exhibits the characteristics of high delamination resistance, damage tolerance, and shear strength. Considering the characteristics of braided structures, two types of high-performance materials, namely, aramid and carbon fibers, were used as reinforcements to prepare braided composites with different hybrid structures. In this study, the longitudinal and transverse shear properties of 3D braided hybrid composites were tested to investigate the influences of hybrid and structural effects. The damage characteristics of 3D braided hybrid composites under short beam shear loading underwent comprehensive morphological analysis via optical microscopy, water-logging ultrasonic scanning, and X-ray micro-computed tomography methods. It is shown that the shear toughness of hybrid braided composite has been improved at certain degrees compared with the pure carbon fiber composite under both transverse and longitudinal directions. The hybrid braided composites with aramid fiber as axial yarn and carbon fiber as braiding yarn exhibited the best shear toughness under transverse shear loading. Meanwhile, the composites with carbon fiber as axial yarn and aramid fiber as braiding yarn demonstrated the best shear toughness in the longitudinal direction. Due to the different distribution of axial and braiding yarns, the transverse shear property of hybrid braided structure excels over the longitudinal shear property. The failure modes of the hybrid braided composite under the two loading directions are considerably different. Under transverse loading, the primary failure mode of the composites is yarn fracture. Under longitudinal loading, the primary failure modes are resin fracture and fiber slip. The extensive interfacial effects and the good deformation capability of the hybrid braided composites can effectively prevent the longitudinal development of internal cracks in the pattern, improving the shear properties of braided composites.
Highlights
The yarns of 3D braided composites intertwined with one another in space to form a highly integrated 3D mesh structure can fundamentally overcome the problems of poor adhesion between layers and easy delamination, and improve the structural integrity and mechanical properties of composites along the thickness direction [1,2]; such composites have been widely used in the aerospace, military, marine, automobile, and other fields [3,4,5]
The shear failure characterization of braided composites with pure carbon and carbon/aramid hybrid is investigated via short beam shear evaluation with different bearing load directions
It has been found that the maximum load, shear strength, and energy absorption capacity of the specimens under transverse loading are higher than those under longitudinal loading because the axial yarn and braided fiber of the specimens under transverse loading share supporting roles
Summary
The yarns of 3D braided composites intertwined with one another in space to form a highly integrated 3D mesh structure can fundamentally overcome the problems of poor adhesion between layers and easy delamination, and improve the structural integrity and mechanical properties of composites along the thickness direction [1,2]; such composites have been widely used in the aerospace, military, marine, automobile, and other fields [3,4,5]. Carbon fiber is widely used in the field of composite materials because of its high tensile strength. Improving the comprehensive mechanical properties of materials by designing in accordance with the structural characteristics of 3D braided composites is highly significant
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