Research On Slamming Damage Of Composite Hull Into Water

Composite material(Fiber Reinforced Plastic, FRP) has high specific strength, high specific stiffness, strong design ability and good anti-fatigue performance, etc., and the composite manufacturing craft can achieve the design concept of high speed, low emission, long life, excellent comfort and so on. So it is widely used in civilian and military shipbuilding industry such as fishing boats and hunt ing minesweepers. With the development of high speed ship, when the hull is separated from the water surface, the phenomenon of slamming is very easy to occur when the ship is into the water again, resulting in damage to the local structure of the composite ship. The generation and propagation of composite damage is a gradual process, and a variety of internal damages are not visible to the naked eye. Therefore, the existence of slamming damage poses a great potential threat to the security of FRP ship.Based on fracture mechanics, damage mechanics and FRP failure criteria, FRP laminate structure model is established using the finite element software ANSYS/LS-DYNA in this paper, and the simulation of low velocity impact damage of FRP laminates structure verifies the correctness of the model. Based on the ALE algorithm and hydrodynamic slamming, the slamming damage mechanis m of FRP laminates was analyzed, and the damage law of FRP laminates under the slamming action was explored. Then the slamming response of different types of composite cabin structure is analyzed. Finally the design scheme of composite hull against slam is determined through the contrast analysis which provides guidance for the future design of the composite ship strike against slam.First of all, to simulate the slamming damage of composite laminates, this paper adopts a new interface element model based on the bonding mechanism and uses strain energy release rate criterion to simulate the interlaminar damage. Single layer plate model is used by Change-Change failure criterion and stiffness degradation criterion to simulate layer damage. The slamming damage mechanism of FRP is analyzed by using FRP laminates model. And the slamming damage failure of composite laminates is studied mainly from the laying up orientation, the plate thickness, the rise angle, the water entry angle and the water entry velocity. Each factor has a great impact on the damages of FRP laminates.Secondly, by using FRP laminate model simulation outer panel, solid element simulation profile structure, the against slam characteristics of the FRP ships used T-shaped stiffened plate frame, one-way hat stiffened panels and two-way hat stiffened plate frame are studied respectively, and the different effects of the outer panel and the aggregate of FRP boat against slam performance are compared and analyzed. It is concluded that the outer plate is the main bearing part of the slamming load.Finally, from the aspects of the skeleton structure of cabin, the size of the aggregate structure and the thickness of hull plate, the against slam performance of composite hull cabin is studied. Through comparative analysis, we get the optimal design scheme of composite hull cabin against slam.The optional scheme of composite ship will provide a reference for the design of anti-slamming composite boat.