Study On The Mechanical Properties Of Shape Memory Alloy Hybrid Composites Subject To Low Velocity Impact

Fiber reinforced composites are widely used in aerospace,medical,and construction fields due to their excellent mechanical properties such as specific stiffness,strength,and fatigue resistance,as well as ease of fabrication and designability.Composites are extremely susceptible to out-of-plane loads during production and use,resulting in invisible damage,mainly including matrix cracking,interlaminar delamination,and fiber breakage.These invisible damages degrade the overall mechanical property of the composites,thereby reducing the safety of the structure.The interfacial adhesion between fiber and matrix is one of the most important factors affecting the properties of composites.Therefore,it is necessary to conduct in-depth research on the interfacial heterogeneity and complex failure mechanism of composites to reveal the debonding damage mechanism,thus improving the reliability of composite structures.In this paper,the low-velocity impact behavior of shape memory alloy(SMA)reinforced foam sandwich panel and the interface performance of SMA fiber/matrix are studied,mainly including the following aspects:(1)Experimental study on the mechanical properties of SMA fiber reinforced composite foam sandwich panels subject to low velocity impact.In this paper,the impact mechanical properties of five new types of SMA foam sandwich panels under 50 J impact energy were studied.The impact mechanical response and damage failure morphology were analyzed to reveal the impact damage failure mechanism.The results show that all sandwich panels experienced penetration failure,including matrix cracking,delamination,interfacial debonding,and fiber breakage.Compared with the traditional sandwich panel,the impact resistance of SMA fiber reinforced foam sandwich panel is improved,the load threshold is increased,and the delamination area is reduced.(2)Numerical simulation of the low velocity impact resistance of SMA fiber reinforced composite laminates.In this paper,the finite element method was used to simulate the progressive damage failure process of SMA fiber reinforced composite laminates.Through the analysis of the impact mechanical responses,impact contact force,displacement,and impact absorption energy over time,as well as the impact damage mode and degree,the enhancement mechanism of SMA fiber on the mechanical properties of composite laminates under low velocity impact is revealed.(3)Numerical simulation of interfacial performance of SMA/resin matrix based on cohesive zone model.Based on the cohesive zone model,a spatially varying tensile strength Weibull random field was mapped onto the finite element mesh of the fiber/matrix interface,and integrated with the cohesive element to capture the complex three-dimensional interfacial debonding behavior.A new SMA single fiber pull-out model was constructed to predict the mechanical behavior of the SMA fiber/resin matrix interfacial debonding,and to analyze the evolution of progressive damage of the SMA/resin matrix interface,revealing the interfacial debonding mechanism.The effects of shape memory alloy aspect ratio and embedding depth on the interfacial properties of SMA/resin matrix were also simulated and studied.