Mechanical response of linear viscoelastic composite laminates incorporating non-isothermal physical aging effects

This paper presents a method of predicting the mechanical response of compo site laminates including the effects of linear viscoelasticity and physical aging. Effective-time theory has been used to characterize the physical ag ing behavior of each linear viscoelastic lamina. In accordance with experim ental findings, the aging behavior of each lamina is allowed to differ in t he shear and transverse directions. The mechanical loading is restricted to the linear range, which decouples the aging and load behavior. A recursive algorithm has been used to solve the hereditary convolution integral that governs the response of each ply. Classical thin-laminate theory is then us ed to assemble the individual ply response equations and determine the over all laminate response to general in-plane force and moment loading. The met hod automatically recovers the ply-level stresses and strains, which are of ten critical to strength and durability predictions. The model can use eith er lamina compliance or modulus properties as its basis. Several illustrati ve examples of long-term laminate response to variable loading are presente d and the impact of physical aging is explored. It is shown that for multid irectional laminates, the stiffness of the lamina in the fiber directions c an allow simplifications of the model. (C) 1999 Elsevier Science Ltd. All r ights reserved.