Effect of Natural Aging on Mechanical Properties of Laminated Composites

Abstract

Composite materials are materials formed by combining two or more components that are macro-dimensionally different from each other. These different materials that make up the structure, age depending on time and environmental conditions like all materials. This aging can occur naturally over time from external factors, or it can be artificially aged by placing the specimen in a certain temperature environment. It is possible to observe some changes in mechanical properties due to the aging process. However, studies involving natural aging are not diverse to determine changed mechanical properties. Since long periods are needed for natural aging, artificial aging under controlled conditions with the help of the special equipment is frequently seen in studies. The aim of this study is to determine the effect of natural aging on elastic constants and the buckling response of laminated composite materials. In order to determine elastic constants of aged and unaged plates, tension and in-plane shear tests are performed on [0]8 and [90]8 E/glass-epoxy composites, respectively. In addition, the effect of natural aging on the buckling load for rectangular plates of various length/thickness ratios, and ply orientation is examined for clamped-clamped boundary conditions. For this purpose, numerical and experimental studies are conducted on aged and unaged specimens. Buckling analysis of the laminated composites is performed by using finite element analysis software ANSYS. Comparisons were made between the test results and predictions from finite element analysis. Good agreement is obtained between the numerical and experimental results. The results show that the long-term natural aging process decreases the elastic constants and buckling load of the composite materials.