Temperature field characteristics of CF/PEEK thermoplastic composites formed by automated fiber placement using hot gas torch with slit structure nozzle

In-situ consolidation forming of high-performance thermoplastic composites by Automated Fiber Placement(AFP)is of significant interest in aerospace.During the laying process,the heating temperature has a great influence on the quality of the formed components.A threedimensional heat transfer finite element model of Carbon Fiber(CF)/Polyether Ether Ketone(PEEK)heated by Slit Structure Nozzle Hot Gas Torch(SSNHGT)assisted AFP is proposed.The influence of gas flow rate,heat transfer distance,and laying speed on heating temperature is analysed.The results show that the overall temperature increases and then decreases as the gas flow rate increases.With the increase in heat transfer distance and laying speed,the overall temperature decreases.Meanwhile,the gas flow rate has the greatest influence on the temperature of CF/PEEK being heated,followed by the laying speed and finally the heat transfer distance.Furthermore,the model can also be extended to other fiber-reinforced polymer composites formed by hot gas torch assisted AFP,which can guide the optimization of process parameters for subsequent heating temperature control.

Fractal Design Boosts Extrusion-Based 3D Printing of Bone-Mimicking Radial-Gradient Scaffolds

Although extrusion-based three-dimensional(EB-3D)printing technique has been widely used in the complex fabrication of bone tissue-engineered scaffolds,a natural bone-like radial-gradient scaffold by this processing method is of huge challenge and still unmet.Inspired by a typical fractal structure of Koch snowflake,for the first time,a fractal-like porous scaffold with a controllable hierarchical gradient in the radial direction is presented via fractal design and then implemented by EB-3D printing.This radial-gradient structure successfully mimics the radially gradual decrease in porosity of natural bone from cancellous bone to cortical bone.First,we create a design-to-fabrication workflow with embedding the graded data on basis of fractal design into digital processing to instruct the extrusion process of fractal-like scaffolds.Further,by a combination of suitable extruded inks,a series of bone-mimicking scaffolds with a 3-iteration fractal-like structure are fabricated to demonstrate their superiority,including radial porosity,mechanical property,and permeability.This study showcases a robust strategy to overcome the limitations of conventional EB-3D printers for the design and fabrication of functionally graded scaffolds,showing great potential in bone tissue engineering.

Fractal Design Boosts Extrusion-Based 3D Printing of Bone-Mimicking Radial-Gradient Scaffolds

Although extrusion-based three-dimensional(EB-3D)printing technique has been widely used in the complex fabrication of bone tissue-engineered scaffolds,a natural bone-like radial-gradient scaffold by this processing method is of huge challenge and still unmet.Inspired by a typical fractal structure of Koch snowflake,for the first time,a fractal-like porous scaffold with a controllable hierarchical gradient in the radial direction is presented via fractal design and then implemented by EB-3D printing.This radial-gradient structure successfully mimics the radially gradual decrease in porosity of natural bone from cancellous bone to cortical bone.First,we create a design-to-fabrication workflow with embedding the graded data on basis of fractal design into digital processing to instruct the extrusion process of fractal-like scaffolds.Further,by a combination of suitable extruded inks,a series of bone-mimicking scaffolds with a 3-iteration fractal-like structure are fabricated to demonstrate their superiority,including radial porosity,mechanical property,and permeability.This study showcases a robust strategy to overcome the limitations of conventional EB-3D printers for the design and fabrication of functionally graded scaffolds,showing great potential in bone tissue engineering.