Damages Simulation Of Laminated Plates Subjected To Low-velocity Impact

Because fiber reinforced laminated plates and shells possess high specific modulus and high specific strength in the fiber direction, they are widely used in the aerospace and ship building etc. However, the transverse strength of the laminated plates and shells is very weak, especially at the interfacial layers which are resin rich zones between interlaminar interfaces with different fiber orientations. Therefore, they are prone to suffer interfacial damages when they are under the action of the low-velocity transverse impact.The most common damages of laminated plates subjected to impact are matrix cracking, matrix crushing, fiber breakage and inter-ply delaminations. Among these damages, delamination and matrix cracking are the most dangerous ones, as they can severely affect the strength and stability of the damaged laminates. When the composite laminated plates are under the action of the low-velocity transverse impact, the adhesive layers between laminates with different fiber direction are very likely to suffer delamination. With the initiation and propogation of the damages, the material properties, such as strength and modulus, are degraded progressively. Usually, the action of low-velocity impact on the laminated plates is represented by the equivalent dynamic force in the impact damage simulation. Although the use of the the equivalent dynamic force is computationally efficient, it is not accurate enough. Therefore the transient dynamic damage simulation of the laminated plates under the action of transverse impact is a proper way to investigate the location and size of the impact damageThis thesis studies the simulation of the dynamic impact damages of laminated plates under the action of low-velocity impact. The thesis is composed of the following three major topics:1. The state of research and development of inter-ply delamination of laminated plates is reviewed, and the proper damage criteria are presented. The various one-step degradation method for the impact damage are discussed..2. The transient dynamic code LS-DYNA is employed to simulate the impact damage propagation of the laminated plates under the action of transverse impact at the center of the plates. The modeling technique of dynamic simulation is explored in order to get more accurate damage simulation. The resulting numerical results are compared with the experimental results, and good agreement is achieved. The effect of material models and failure criteria on the inter-ply delamination and matrix cracking is also investigated.3. The accuracy of the delamination simulation using the equivalent dynamic forces for the impactor is evaluated based on the experimental results and the impact damage simulation using the transient dynamic impact simulation.