The Research Of Fracture External Fixator Based On Shape Memory Polymers

Shape memory polymer is a class of smart material which can produce the large recoverable deformation under the external excitation condition.It has a structure carrying capacity and an active deformation function.Nowadays, the shape memory polymer is designed to be biocompatible, controlled biodegradable and have other biological characteristics, so it has been widely applied to the field of the biomedicine.Fracture is a common Trauma in daily life, however,for traditional methods of fracture treatment there are still many technical problems that can not be overcome.For example,the tightness of plaster bandage is difficult to control, easy to compress tissue and cause allergies.The latter fractured limb may be displaced due to loose tube type.In this paper,focused on the traditional method of fracture treatment problems and defects,it provides a stable, plastic, elastic adjustable, lightweight external fixator based on shape memory polymers.(1)Introduce the biological and the mechanical characterization of shape memory polymers.By dynamic mechanical analysis(DMA) experiments, isothermal creep, stress relaxation and fatigue experiment to characterize the basic thermal mechanical properties, the related material constants are obtained.(2)Base on Tobushi’s proposed shape memory polymer viscoelastic constitutive theory, and extend from one-dimensional to three-dimensional. For ABAQUS secondary development,it can be imported into ABAQUS UMAT subroutine which has realized the simulation of the thermodynamic behavior of shape memory polymer.This paper simulates the shape memory process through the steps of heating and loading,cooling and unloading and reloading to simulate the deformation of shape memory polymer and the initiative back to the original shape.(3)The helical structure of shape memory polymer is designed, and the external fixation model of tibiofibula and femoral fracture are established respectively.By using ABAQUS finite element software the stress,the strain and the displacement of the screw and human body are analyzed. And then infer the reliability of the structure and calculate the small displacement of the human body at the broken ends.(4)Introduced the process and the fabrication of the external fixator based on shape memory polymers in detail. Then the adaptive response of shape memory polymer is verified by experiments, which can reflect the operability and the superior performance of the external fixator.