Research On Low Velocity Impact And Compression Of Composite Hat-shaped Panel

Hat-shaped composite material stiffened plate is widely used in aircraft design because of its closed characteristics and strong shear resistance.In engineering practice,composite material stiffened plates are very sensitive to low-velocity impacts.Low-velocity impacts are often not given enough attention.Some potential hazards are easily overlooked and have a greater impact on the safety and reliability of the structure.Firstly,the purpose of this article is to study the factors that affect impact damage and the impact of impact damage on the load-bearing capacity of stiffened plates.The low-velocity impact and the residual strength after compression of large-scale composite hat-shaped stiffened plate structures are studied.Some more data about test and compression test after impact are supplemented by finite element analysis.Secondly,in the low-velocity impact test,the method of falling-weight impact is used,and the depth of the pit after the impact of the stiffened plate is determined by visual inspection and ultrasonic A-scan equipment to determine the location and size of the damage.By studying the influence of different factors such as rib spacing,solidification form,impact head distance from ribs,etc.on impact damage.It can be concluded that different factors affect the impact damage.It was found that the depth of the pit has a great relationship with the position of the impact point,and the impact resistance of the skin between the ribs is significantly lower than the impact point near the ribs.The spacing of the ribs mainly affects the impact resistance of the P4 series points,and the curing method has a greater impact on the rebound effect of the impact point.The initial impact damage of the co-bonded stiffened plate is greater than that of the co-cured stiffened plate,but the rebound effect of the pit more obvious.Finally,in the axial compression test,electric measurement and digital image correlation technology were used to test the full-field deformation and buckling,damage process,and numerical simulation was carried out.When the maximum displacement is reached,the kinetic energy drops to zero.With the rebound of the impact head,the energy is transferred back to the impact head in the form of kinetic energy.The stress in the entire impact process increases first and then decreases.Because of the energy loss during the impact,the final kinetic energy is slightly lower than the initial kinetic energy.The energy loss at points P2 and P3 is within 10%,and the energy dissipation at points P1 and P4 series exceeds 15%.The damage forms of each impact point are mainly fiber tensile damage and matrix tensile damage.The damage location of point P1 is located at the rib,while the other points are on the skin.Among them,the damage area of the P4 series impact points is relatively large,and the damage area of the P3 point is the smallest.The shape of the impact damage received by each layer is related to the ply angle.In the axial compression test,electric measurement and digital image correlation technology were used to test the full-field deformation,buckling and damage process,and the process of low-velocity impact and compression was simulated by finite element simulation.The buckling load or ultimate load of the stiffened plate after impact is significantly smaller than that of the non-destructive stiffened plate.Among them,the load-carrying capacity of the three kinds of stiffened plates with 210 mm rib spacing decreased by 5.01%,18.2% and 10.1%,while the load-carrying capacity of the 260 mm rib spacing with stiffened plates decreased by30.8%,22.8% and 17.9%.The stiffened plate has obvious buckling during the axial compression test,and the buckling position is mainly concentrated in the middle of the stiffened plate.This area is also near the impact point,indicating that the damage caused by the impact pit caused the test piece A relatively large bending deformation occurred.The error between the test results and the finite element results is not large.The main failure mode is the tensile failure of the matrix.It shows that the ultimate load and residual strength of the stiffened plate after impact damage have been significantly reduced,which has a significant impact on the bearing capacity of the stiffened plate.