Study On Factors Affecting Impact Resistance Of Double-sided Adhesively Bonded Repair CFRP Laminate Structures

CFRP(Carbon Fiber Reinforced Polymer)composites are widely used in aerospace field because of their excellent properties.Due to the invisible damage of composite materials under low-speed impact,it is necessary to repair the damaged parts.One of the common repair methods is bonded repair.In this paper,the influence of patch parameters on the impact-resistance of CFRP laminates repaired by double-sided bonded repair is studied by means of experiment and numerical analysis,and the patches are optimized to make the repair structures have better impact resistance.Firstly,based on the continuum damage mechanics,the bonding element model,and combined with VUMAT user material subroutine,a three-dimensional finite element model of CFRP laminates repaired by double-sided bonded patches with low-speed impact was constructed.Then,a low-speed impact test platform for CFRP laminates was built,and the experimental force curves and impact energy curves were discussed.The validity of the finite element model of low-speed impact for CFRP laminates repaired by double-sided bonded patches was verified by the test.Secondly,the influence of single parameters of the patch on the impact-resistance of repaired structure was studied.The impact-resistance of repaired structure was measured by the values of delamination area and absorbed energy.The results show that repaired structure with the circular patch has good impact-resistance.When the patch radius is 2.5r,the energy absorbed by the repaired structure and the delamination area of the repaired structure are in a low level.When the patch thickness is 0.45 mm,or the patch off-axis angle is 0 degree,the repaired structure shows better impact resistance.Finally,a surrogate model was proposed based on DOE and Diffuse Approximation method.Through the surrogate model,the optimal combination of patch parameters considering patch thickness,patch radius and patch off-axis angle was determined.The optimization result shows that the repaired structure has the best impact-resistance when the radius of patch is 10.50 mm,the thickness of patch is 0.44 mm and the off-axis angle of patch is 28.42 degrees.