Prediction Of Damage Behavior In Carbon Fiber Reinforced Magnesium Alloy Laminates Under Repeated Low Velocity Impact

Fiber-metal laminates(FMLs)are novel hybrid composites structure formed from the combination of metal layers sandwiching fiber-reinforced composite layers.Due to their excellent mechanical properties,FMLs have been widely used in the aerospace and other fields.As the lightest structural alloys in engineering applications,FMLs made of magnesium alloys and fibers have potential application values.In order to explore the impact resistant properties of AZ31 B magnesium alloy laminates(Mg/CFRP)reinforced by carbon fiber reinforced composites,a simulation study was performed on the low velocity impact behavior of single and repeatedly impacted Mg/CFRP using ABAQUS/Explicit.The damage behavior of metal layers and fiber plies as well as their interfacial debonding were studied in detail.Interfacial debonding is an important failure mode of FMLs subjected to low velocity impact.In order to simulate the interface debonding process accurately,the exponential cohesive zone model(CZM)describing the interfacial debonding behavior was studied.Based on the CZM,the interface constitutive model was implemented in a user-defined subroutine VUMAT for ABAQUS/Explicit by Fortran language.The VUMAT was validated through consistent comparison between the interfacial debonding simulation predictions and the corresponding experiment data.On this basis,the impact response of FMLs and the interfacial debonding in them were further simulated by using the VUMAT subroutine.Based on 3D Hashin failure criteria and reduction of failed elements,the corresponding VUMAT subroutine was compiled to predict the dynamic impact response and damage behavior of fiber plies;while magnesium alloy was modeled through an anisotropic plastic constitutive model.The numerical simulations of low velocity drop weight impact tests on AZ31 B magnesium alloy laminates(Mg/GFRP)reinforced with glass fiber were first carried out and it is shown that the simulation results are in good agreement with the experimental data.Then the single low-velocity impact behaviors of the Mg/CFRP and hybrid fiber reinforced Mg laminates were numerically investigated.It is found that compared with a single carbon fiber reinforced epoxy composite/magnesium alloy laminate,a single glass fiber reinforced epoxy composite/magnesium alloy laminate has smaller cracks under an impact load,but the former has better impact deformation resistant capacity than that of the latter.Hybrid carbon fiber and glass fiber composite laminates can provide the best impact-resistant properties when the glass layers are at the suitable position.In order to explore the damage mode of Mg/CFRP laminates under the repeated low-velocity impact loading,the repeated impact process was simulated and the effects of different fiber stacking sequences and metal volume fractions on the impact resistant properties were studied in this paper.The results show that the matrix cracking firstly occurred in the impacted side under the repeated low-velocity impact loading.The impact resistant properties are better when the fiber stacking sequence is / /0 90 9 /0 0° ° ° ° within the scope of the study.The higher the volume fraction of the metal layer,the smaller the cracking occurred after the first impact,but the cracking of the laminates spreads faster with the increase of impact times.