A Procedure for the Numerical Determination of the Strength Criterion Parameters of a Three-Dimensionally Reinforced Composite Material

A numerical procedure for determining the parameters of the quadratic strength criterion for composite materials is presented, which considers the difference in tensile and compressive ultimate stresses. In addition to the reinforcement geometry, the elastic properties and ultimate stresses of fibers and the matrix are used as input data. The developed approach is based on the finite element modeling of a representative element of the volume of a three-dimensionally reinforced composite material. The boundary conditions are formulated, which makes it possible to reproduce the stress state within this volume under different types of homogeneous (on average) loads of the composite material. The local maximum equivalent stresses were determined separately for fibers and the matrix, which were used to determine the calculated ultimate stresses of the composite. The numerical results for flat specimens under tension in two directions and shear in the specimen plane were experimentally verified. The maximum difference between the calculated and experimental values of ultimate stress is 6.13%, which makes it possible to use the proposed procedure in design works.