The Establishment And Numerical Simulation Of Polyimide Constitutive Model

Polyimide(PI) is being widely used as a kind of special engineering materials in the aerospace, microelectronics, nanotechnology, LCD, laser and other fields. The most important performance is mechanical properties, so it is necessary to study it. The finite element simulation technology is widely used for its advantages such as high efficiency and low cost, but the ANSYS software for polymer material model is relatively small, less suitable for PI, this limiting the use of the software. Therefore, to establish constitutive model for PI materials, and apply it in the numerical simulation of ANSYS software simulation is very necessary and meaningful.In this paper, PI specimen is made in different temperature and strain rate of uniaxial tensile test, in INSTRON5848 micro force test machine, getting the stress-strain curve under different conditions. The experimental results show that PI has obvious correlation between strain rate and temperature, when strain increased or the temperature falls, tensile strength, yield strength and elastic modulus are increased, elongation at break decreases.On the basis of a lot of physical experiment, we set up and optimize the constitutive model of PI, using numerical simulation model, then the calculated and experimental results are compared and analyzed. Firstly, we should establish a model, to determine parameters, and optimize the model. Secondly, we use the secondary development function of ANSYS software, choose the right stress update algorithm, write the polyimide constitutive model user subroutine and through the simulation of the unit drawing to verify the feasibility of the subroutine. Finally, we use the programmed user subroutine to the PI specimen for different temperature and different strain rate of numerical simulation of tensile. To simulate the stress-strain curve compared with corresponding experimental curve under the condition of curve, results show that the general trend is consistent, the error is within 25%, which verifies the correctness of the user subroutine.