Research On Tensile Failure Behavior Of Composite Laminates After Impact

As a new kind of material, composite materials have many merits such as high specific strength, high specific stiffness, high fatigue performance, good designable characteristic and high corrosion resistance ability. Nowadays, composite materials have been applied widely in aircraft structures. The impact damages will result in matrix crack, fiber breakage, delamination and so on, which can largely decrease the residual strength and fatigue performance. Therefore, it's very important to research the residual strength of composite materials after impact.In order to analysis the residual tensile strength of composite laminates after impact, a three dimentional equivalent damage model is proposed, which is based on equivalent damage model and three dimentional finite element analysis. Based on ABAQUS, a user subroutine to define a material's mechanical behavior (UMAT) is developed. Compared with the experimental result, the analysis tensile strength is accurate.The main research works done in the dissertation include(1) An equivalent hole model is proposed to predict the residual tensile strength of composite materials after impact and simulate the damage process of composite under tensile loading. Therefore, the tensile strength of composite materials after impact turns to the tensile strength of composite materials with an equivalent hole.(2) In this research, we use three dimension Hashin damage criteria and Camanho material deterioration, and build a three dimensional analysis model.(3) The ply angle can affect the matrix tensile and shear strength, hence, an in situ ply matrix tensile and shear strength formula proposed by Chang K Y is applied in this paper. Every ply is given different properties. In addition, a user subroutine to define a material`s mechanical behavior (UMAT) is developed in ABAQUS.(4) With the three dimensional model proposed in this paper, we predict the residual tensile strength of composite with a hole and simulate the damage process under tensile loading. The residual tensile strength of composite with impact damage and the damage process are also predicted and simulated.