A univariate iterative correction strength prediction method for composites considering residual stresses

Abstract

Traditional strength-ratio prediction method has limitations in considering residual stresses and is prone to misjudging failure modes at low mechanical stress states. To solve this problem, a univariate iterative correction strength prediction method is proposed in this paper. The method considers the residual stress as a constant value and adjusts the mechanical stress variable coefficients iteratively to update the synthetic stress state and make a failure judgment. Case validation shows that the method can accurately predict the damage modes and ultimate loads of composites independent of the mechanical stress levels. Further studies reveal that the residual stress significantly reduces the tensile strength of the laminate (up to 50.8 %) and changes the failure modes (matrix compression failure to tensile failure); the residual stress has a translational effect on the failure envelope, which alters the overall damage envelope of the laminate by translating the damage curves of each single ply. In addition, the proposed residual strength concept can simplify the stress analysis process. The research results provide theoretical support for structural design and strength assessment of composite materials.