Numerical investigation on auxetic angle-ply CFRP composite laminates under low-velocity impact loading

Materials with a negative Poisson's ratio are known as auxetic materials, which are highly desirable for improved resistance to indentation and impact. Angle-ply composite laminates with high anisotropy exhibit auxetic behavior within a specific range of layup angles. In this research, the influence of negative Poisson's ratio on the mechanical response and the enhancement of the damage behavior of carbon/epoxy composite laminates under low-velocity impact has been numerically investigated. For this purpose, a MATLAB code based on classical lamination theory relationships was developed to determine the range of layup angles to achieve both negative Poisson's ratio in-plane and through-thickness (out-of-plane). Then, the layups with the most negative through-thickness and in-plane Poisson's ratio values were selected. Also, two new stacking sequences were investigated so that both of them partially exhibited the characteristic of negative through-thickness and in-plane Poisson's ratio. The progressive damage model is written and implemented using a computer code in the Abaqus user-material subroutine. The progressive damage model consists of Hashin and Puck failure criteria and the damage evolution model based on the equivalent strain method to predict the initiation and evolution of damage for matrix and fiber. The results indicate that the new laminate configurations have 66% higher effective longitudinal modulus and 173% higher effective transverse modulus compared to the in-plane and through-thickness auxetic ones, respectively. In addition, the proposed configurations showed less overall damage under low-velocity impact loading compared to the auxetic laminates. Based on the investigations, the new configurations with features such as high impact force, low impact time, and low maximum displacement could be suitable for use in structures with a hardwall design approach.