Study On The Low Velocity Impact Mechanical Performance Of Composite Laminates With Shape Memory Alloy

Fiber-reinforced resin matrix composites have lots of advantages such as the higher modulus and strength to mass ratio,simple preparation and easy processing,which have been widely applied in aerospace,automobile industry and construction area etc.However,due to the relatively poor impact resistance,invisible damage can be easily induced in composites subjected to out-of-plane impact loading,the impact damage such as matrix cracking and delamination,will make the overall mechanical properties of composites reduced,which makes a negative influence on the security application of composites for long service life,so the study on the impact resistance and improvement methods of composites is very important.As composites are sensitive to the low-velocity impact,the method of incorporating shape memory alloys(SMA)into the composites is used to improve the impact resistance of composites.The hyperelastic property of SMA makes it the better capacity to dissipating energy,when SMA fibers are embedded into composites,they can effectively reduce the impact damage of composites,so the impact resistance of composites is improved.In this paper,the low velocity impact behavior of SMA hybrid composites has been studied by experimental and finite element simulation methods.The main contents are the following:Firstly,the vacuum assisted resin infusion(VARI)molding process was used to prepare basalt fiber-reinforced composite laminates without and with SMA fibers.The composite laminates containing two perpendicular layers of SMA fibers were divided into four types according to position of SMA fibers.The low-velocity impact tests were carried out at three different impact energies(30J,60J and 90J)for each kind of composite laminates.The macroscopic and microscopic damage morphology and the impact mechanical responses(impact contact force-time curve,displacement-time curve and absorbed energy-time curve)were analysed to determine the effect of SMA fibers on the impact resistance of composite laminates subjected to low-velocity impact test.The experimental results show that the low-velocity impact resistance of composite laminates is effectively improved by embedding SMA fibers.Compared to the traditional composite laminates,the impact contact force of the SMA hybrid composite laminates is increased,the impact damage and the deflection are decreased and the recoverable energy is also increased.Compared with other modes,better impact resistance of composite laminate is achieved with one layer of SMA fibers embedded into the top of the laminate and another layer the bottom.Then,the VARI process was again applied to prepare the SMA fiber reinforced foam core sandwich panels.The facesheets were made of glass fiber-reinforced composite laminates without and with one layer or two layers of SMA fibers,the core was polyvinyl chloride foam.The influences of eight kinds of location of SMA fibers on the impact resistance of foam core sandwich panels subjected to 35J impact energy were studied.The macroscopic and microscopic damage morphology and impact responses of impacted sandwich samples were analysed to reveal the effects of SMA fibers on the low-velocity mechanical behavior of foam core sandwich panles.The experimental results show that the impact resistance of SMA fibers reinforced foam core sandwich panels is enhanced compared to the traditional sandwich panels,the improvement of impact performance of sandwich panel is more apparent with SMA fibers incorporated into the bottom of the facesheet,and the impact resistance of sandwich panels with two layers of SMA fibers is better than the ones with one layer of SMA fibersAt last,the low-velocity impact mechanical behavior of SMA fiber reinforced foam core sandwich panels was simulated by a three dimensional finite element model,the simulation results were basically consistent with the experimental results.the impact mechanical behavior of SMA fiber reinforced sandwich panels subjected to different impact energies was studied by the validated model,the trend of the impact responses of sandwich panels to the impact energy was revealed,the critical impact energies to penetrate the front facesheet and to break the rear facesheet were predicted.The effect of SMA fiber quantity on the impact mechanical behavior of SMA fiber reinforced foam core sandwich panels was further studied,the simulated results showed that the more SMA fibers were embedded,the less the impact damage of sandwich panels was induced and the better the impact resistance of sandwich panels was achieved.