Research On Low Velocity Impact Damage Of Composite Hull

Composites ship has good propulsive performance, good stability, stronganti-windability, energy conservation, environmental protection and so on. Thismakes it widely be used in military and civilian industries such as fishing vessel,yacht, mine sweeper and hunter, frigate. However, the transverse strength of FiberReinforced Plastics (FRP) is weak in the thickness direction, particularly theadhesive layer between the plies. When composite ship is subjected to variousimpact such as the heavy fall, ship impacting wharf, collision between ships, impactdamage will be produced which is not likely to be observed. If the damage reaches acertain level, it will result in the ship-crack, breaking and even sinking. Therefore,low velocity impact poses a great risk of the structure of composites ship.Based on fracture mechanics, damage mechanics and FRP failure criteria, lowvelocity impact damage model of FRP laminate structure is established in this paper.First, low velocity impact composite damage mechanisms are studied to explore thedamage rule in detail. Then the low velocity impact responses of the composite hullcabin structures are analyzed. Finally the optimal impact design of the hull is gotthrough comparative analysis which will provide a reference for the design shock ofships in the future.Based on fracture mechanics and adhesive theory, a new scheme of theadhesive element is put forward to composite low velocity impact damage failure.Chang-Chang failure criteria and stiffness degradation criteria are used in the model.This model is used to analyze the mechanism of the composite low velocity impactdamage which considers delamination and inner-damage. Low velocity impactdamage failure of composite flat plate, shell, stiffened shell was studied from theradius of curvature, impact energy, laminated projects and the boundary conditionsin detail. The impact damage responses of the shell are compared with the flat panelfrom different factors. The impact responses of sandwich structures are comparedwith T-stiffened shell.A two-dimensional shell element is proposed to simulate real hat sections. Andsolid element is used to simulate sandwich structures. The impact properties ofone-way hat stiffened plate frame, two-way hat stiffened plate frame and sandwichstructures are studied, which are common structures of composite ship. The rules ofthe outer plate and the stiffener are investigated by comparing the impact responses.Meanwhile the impact performance of sandwich core material is analyzed in detail.Finally, the impact resistance of the composite hull cabin is studied. The formof the frame structure, the stiffeners size and skin thickness are compared. A optimization is made for a good impact impact resistance design. The optimalimpact design of the hull will provide a reference for the design shock of ships.