Electro-Thermal Activated Deformation Behaviour Of Over-Braiding Circular Tube With Carbon Fiber Reinforced Shape Memory Polyurethane Filament

Shape memory polyurethane(SMPU)circular tube is a smart structure design,having been engaged in various applications such as medical and aerospace.Due to the thermal-activated SMPU is non-conducting and its low stiffness and strength under high temperature.Some conductive components are needed to combine with the SMPU for reinforcing the mechanical characteristic and achieving remote control under electric Joule heat.Here we prepared an electro-activated shape memory composite tube incorporated with continuous carbon fiber(CCF)/SMPU filaments by extrusion method.The composite filaments used SMPU as the matrix and CCF as the reinforcing phase.The shape memory composite braided tubes exhibit high strength and recovery force and excellent electro-thermal activated shape memory performance.The research contents are as follows:(1)The interface bonding performance of CCF/SMPU composite filament has been investigated.The influence of continuous carbon fiber on the thermal and thermodynamic properties,as well as modulus and strength of composite filaments has been analyzed.(2)The relationships among radial and axial mechanical compression properties of diamond braided circular tube in braiding angle,interlaced point state and filament type have been revealed.The influence of braided layers on the axial tensile mechanical properties of regular braided circular tubes has been explored.(3)The relationship between shape memory performance and braided structure parameters under environmental thermal stimulation has been studied.The shape recovery mechanism of radial and axial compression at different stimulus temperatures has been explored.The enhancement effect of CCF on shape memory of CCF/SMPU composite circular tubes has been verified.(4)The shape memory electrothermal coupling mechanism of regular braided composite circular tubes under different activated voltages has been revealed.The shape recovery force test system has been designed,and the relationship between recovery force and applied voltage has been investigated.We have found that:(1)The introduction of CCF forms excellent interfacial bonding performance of CCF/SMPU composite filaments.The fluidity of interfacial molecules reduces,leading to a higher glass transition temperature range.The tensile strength and modulus of CCF/SMPU composite filament are enhanced by continuous carbon fiber.(2)The braided circular tubes with different braiding angles exhibit obvious diversity in radial mechanical compression strength.With the braiding angle increases,radial compression load enhances and compression hysteresis intensified.The axial compression load is positively correlated to braiding angle and the diamond braided tubes with braiding angle 60° exhibit excellent axial compressive properties.The fixed interlaced point shows smaller slippage and reorientation of filaments than free interlaced point,and achieves higher compression load.The axial tensile strength enhances with increasing braided layers.(3)The diamond braided tubes exhibit excellent thermal-activated shape memory performance.The highest radial and axial compression shape recovery ratio of diamond braided tubes can reach 91.47% and 100%,respectively.The shape recovery performance is best at a braiding angle of to 45°.The fixed interlaced point has better shape memory characteristics than free interlaced point.As the recovery temperature increases,recovery speed rate and recovery ratio are both enhanced.(4)Regular braided composite circular tubes present excellent shape memory properties of low voltage drive,high recovery ratio and recovery force.The shape recovery ratio is positively correlated with the number of braided layers under lower voltage.The resistance decreases with increasing braided layers and the rapid electrothermal conversion efficiency achieves excellent shape memory recovery.Excessive heat is generated when the voltage rises above 6V,resulting in a decrease in the recovery ratio and maximum recovery force.