Development and Application of a Model Using Center of Gravity of Hysteresis Loops to Predict Fatigue Damage Accumulation in Fiber-reinforced Plastic Laminates

Abstract

A new methodology for modeling fatigue damage accumulation in fiber-reinforced plastic (FRP) laminates is introduced. This new model, termed the CG method, or the CG Model, utilizes the center of gravity (CG) of hysteresis loops (HL). It is inspired by previous investigations into damage accumulation models based on HL, such as maximum displacement (the width of the HL), energy dissipation (the area of the HL), plastic strain (the width of the interior part of the HL), and stiffness reduction. The CG method combines all these models, relates them to each other, and presents very consistent results. The CG model is especially helpful in cases where the other models cannot be used. This study shows that using the CG model a set of straight lines is created that present the evolution of the positions of the CG of the HLs during fatigue tests. These ‘curves’ may then be employed to build the complete set of curves that, even for untested specimens at different stress levels, accurately predict fatigue damage accumulation in FRP laminates. Employing this method also provides more insight into the damage condition of the specimen than other models allow.