| Metal-Thermoplastic carbon fiber composite laminates are essential materials for achieving the significant need to meet the safe weight reduction of impact resistant-structural components in the aerospace,defense,transportation,and other fields.This hybrid material usually consists of aluminum alloy mixed with carbon fiber reinforced thermoplastic composites(CFRTP),which combines the outstanding advantages of high impact toughness of aluminum alloy and high crack expansion resistance and damage tolerance of CFRTP.In addition,the CFRTP requires no curing and short molding time,making it possible to process fiber-metal hybrid laminated structures with high efficiency and low cost.However,the thermophysical properties of Al alloys,CFRTP,and other heterogeneous materials vary greatly,making it challenging to achieve synergistic rheology and uniform deformation.And the interface bonding mechanism between heterogeneous materials is unclear.These result in formed components with low interfacial strength,porous defects,and poor interlayer performance,which hardly meet basic device design and use requirements in aerospace,transportation,and other fields.Thus,primary molding interface and mechanism research are urgently needed to form a high-efficiency and high-performance molding process specification for thermoplastic fiber-metal composite laminates.This paper focused on the one-step hot stamping forming process of Al/CF/PEEK hybrid V-shaped structural parts formed by mixing 6061 aluminum alloy and polyetheretherketone resin-based CFRP(PEEK-CF).Combining the bonding-forming process experiment,the macromicroscopic characteristics of the bonding-forming interface and forming performance,the influence law and mechanism of the surface treatment method and bonding-forming process parameters on the interface strength of Al/PEEK and CFRP/PEEK were revealed.Further,stable surface treatment and bonding-forming process systems were proposed to achieve stable forming of Al/CF/PEEK hybrid V-shaped structural parts.The main research contents of the paper are as follows:(1)To enhance the adhesive bonding strength of 6061 aluminum alloy and PEEK adhesive,orthogonal experimental research was conducted on the polishing-phosphoric acid anodizing process of 6061 alloys.Besides,the mechanism,the effect of the anodizing process on improving the bond strength,was revealed by studying the substrate interface’s microscopic morphology and physicochemical properties.The results show that phosphoric acid anodizing under proper conditions can change the failure form of the bonded joint between 6061 alloys/PEEK as well as improve the performance of the joint.The appropriate number of circular pits and nano-scale holes on the surface of the anodized aluminum alloy film is the key to improving the shear strength of the joint.(2)A V-bending stamping die with an integrated autonomous positioning,support,and stamping structure was designed and fabricated,based on the hot stamping one-step forming process route.Combined with DIC digital correlation technology,the load-displacement response,local strain field,local displacement field,and failure process of hot stamping one-step forming V-shaped hybrid members under four-point bending loading with different surface treatment processes were tested and analyzed.The results indicated that the surface bonding of the anodized aluminum alloy is significantly enhanced,which ensures the effective load transfer during the bending loading process.Moreover,the failure of the hybrid member is transformed into the interlaminar failure of the CFRP composite,and the mechanical properties of the hybrid member are greatly improved.(3)The formed components’ macroscopic deformation size and mechanical properties,microscopic interface structure,and failure morphology of the formed components were tested and analyzed.Thus,the influence of stamping speed and forming pressure on the macroscopic and microscopic structure and properties of V-shaped hybrid components was comprehensively evaluated.The results revealed that stamping speed can optimize the spring-back angle of the formed parts,but high stamping speed is not conducive to the forming performance of the components.The forming pressure significantly influences the effective bonding at the joint interface of the hybrid components.The unsuitable pressure will cause different forms of poor adhesion,resulting in multiple cracks and minor delamination of the CFRP composite layer during the loading process and reducing the overall mechanical properties of the component.On this basis,a suitable range of parameters for stamping speed and forming pressure is proposed.Full total figures 71,tables 12,references 79. |
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