Research On Low Velocity Impact Damage Of Stitched Stiffened Panel

Composite laminates have been widely used in aeronautics and astronautics industry because oftheir advantages of high specific strength, high specific stiffness and designable. For the traditionallaminates, inter delaminations can be easily produced by low-velocity impact, which limits theadvantage of composite laminates. By introducing stitched lines in the thickness direction to stiffenedpanels, stitched stiffened panels not only improve the inter-laminar impact resistance but also retainthe advantages of traditional composite laminates, which offers them broad application prospects. Theresearch on low-velocity impact damage of stitched stiffened panels has considerable theoreticalsignificance and application value.A3D dynamic finite element model was proposed to predict the progressive damage of stitchedand stiffened laminates under low-velocity impact, in which the laminate and stiffener were simulatedby brick element, the interface was modeled by cohesive element and stitching thread was realized bybar element. The strain-based Hashin criterion was employed to determine the inter-laminar damagesand the stiffness reduction was used to simulate the in-plane damage evolution. The stress-basedquadratic criterion was employed to evaluate the initial damage of interface, and the bilinear modelwas adopted to degrade the properties of damaged interface. The reasonability of the model wasvalidated by the comparison between the numerical results and experimental data. There were severalmeaningful conclusions by comparing the impact response and damage progression of stitched andunstitched stiffened panels and discussing several influencing factors, which include impact energy,impact location, stitched parameters and stiffener’s form, of low-velocity impact on stitched stiffenedpanels.