Modeling of Relaxation Behavior of Composite Materials

Advanced polymer matrix composites are gaining significance in modern products and technology due to their exceptional attributes which are unattainable by conventional materials. Understanding the mechanical degradation of polymer-based materials is of practical importance in improving the reliability and lifespan of the associated structures and systems. This paper aims to approach, investigate, and analyze the viscoelastic behavior of glass fiber-reinforced epoxy composite through the stress relaxation phenomenon. This was achieved by conducting uniaxial tensile stress relaxation tests and then constructing a numerical model based on the generalized Maxwell model and the Prony series. The experimental results showed that the relaxation of normalized stress (ratio of the instantaneous stress to the initial relaxation stress) does not depend on the loading process. The viscous model with the Prony series of three components successfully predicted the influence of stress loading history on the stress relaxation behavior of glass fiber-reinforced epoxy composite, which was in close agreement with experimental observations (error less than 5%). Consequently, it can be concluded that the developed simple Maxwell material model allows to predict the relaxation behavior of resin-based composite materials.