Research On Model Of SMA-FRP Composite Laminate Subjected To Hydro-Thermal-Mechanical Loading

Shape memory alloy fiber reinforced polymer(SMA-FRP),which combines the advantages of shape changing,damage repairing and mechanical quality improving,can meet the maneuverability of aircraft and have the characteristics of light weight,high strength and hydrothermal resistance as smart composite material.The composite structure of aircraft is subject to thermal cycle,moisture absorption-dehumidification cycle,and the fatigue will be produced,which weakens the mechanical properties.A large number of experimental and certain theoretical studies have been conducted on the strength and damage analysis of CFRP composite materials under hydrothermal conditions,while the research of SMA-FRP as smart material in this area is lacked.Although the literature has been analyzed for the external effects on SMA-FRP,however,the damage caused by the internal strain induced by the hygroscopic cycle and cycles of temperature change need to be counted.Therefore,an accurate hydrothermal fatigue strength analysis method of SMA-FRP is supposed to be developed,which provides a strong support for predicting and evaluating resistance to damage after hydrothermal cycling.A hydro-thermal-micromechanical model of SMA-FRP composite based on Eshelby's equivalent inclusion method and Mori-Tanaka's homogenization theory is introduced first.The inelastic strain tensor of the material,that is,phase transformation strain,thermal strain and hygroscopic strain,are integrated into homogeneous form by this constitutive model,and the effective value of macro-mechanical properties of overall material is also characterized.The simplification of single-layer SMA-FRP composite under uniaxial tensile is analyzed by homogenization theoretical model as well.The superelasticity of SMA-FRP under different hydrothermal preloading is simulated.Temperature changing and moisture absorption have opposite effects on the overall stress.Setting different fiber contents,it is simulated that the phase transformation process inside the SMA fiber is not controlled by its volume fraction change.Subsequently,the SMA-FRP hydro-thermal-micromechanical damage constitutive model is established simultaneously with bringing in damage factor caused by hydrothermal cycles.The numerical simulation results of SMA-FRP degradation under thermal loading,moisture absorption loading and hydrothermal loading verify that the change of coupling cycle significantly aggravates the material damage accumulation process.Finally,based on the ABAQUS software,the uniaxial tensile progressive damage simulation analysis of the material with hydrothermal fatigue is implemented,inducing the evolution process from the initial damage to the final failure of the laminate.This method can systematically break down the effects of complex loading on the failure behavior of SMA-FRP materials under uniaxial tensile conditions.