Reliability Analysis On The Impact Reponse Of Stiffened Composite Panels

The composite material in the process of use will inevitably be affected by the threat of the impact. Low speed impact will cause the visible damage of the material which brings difficulty of maintenance. So, it is very necessary to study the response and reliability of composites for low speed impact.In this paper, we use finite element software ABAQUS. The model uses solid element C3D8 R and interface element Cohesive which add between each layer instead of the adhesive layers. The paper adopts Hashin criteria and user subroutine VUMAT which is used to control the degradation of material properties caused by the adsorption of energy during the low velocity impact of composite materials. Based on the finite element simulation, the paper finds the relationship between the impact and energy, the variation trend of the impact curve,the relationship between the damage area and energy. The simulation results of response and damage are in good agreement.Then this paper establishes a stiffened composite panel model in order to simulate the low velocity impact with the same process of composite laminates. Because of the stiffener,the impact force and damage area in three different locations are discussed. Through the simulation, we find that the stiffener strengthens local stiffness, and adsorbs most of the impact energy, reduces the damage of the material degradation, increases the ability of anti-impact. Then we also found magnitude of the impact force is proportional to the distance from the impact point to the stiffener, and the damage area is inversely proportional.The stiffened plate in low velocity impact simulation is used to analyze the reliability in the classical response surface method. The common composite damage forms, tensile and compression of fiber and matrix damage limit state equation are established. It is considered that in the impact process one point of the composites is destroyed, then the composites is not available. Through ISIGHT, ABAQUS and MATLAB software, four response surface functions are established. The results show that the impact speed is the most influential to the reliability and the composite material is very easy to be threaten by the impact.