Investigation of scaling effects on post-fatigue residual strength of Nanoclay added GFRP composites

This paper describes the evaluation of postfatigue residual strength of scaled laminated composites. The effect of thickness size effects of two scaled specimens on residual strength and stiffness of glass fiber reinforced plastic (GFRP) laminate with neat epoxy matrix and Nanoclay (Nanomer® I.30E) containing epoxy matrix are presented in this paper. The residual strength of a both scaled GFRP specimens with neat epoxy matrix and containing Nanoclay of 3% is determined by conducting tensile test on fatigue cycled after 2,00,000 cycles (R=0.1). Tensile strength, residual strength and stiffness of both scaled specimens are compared with baseline or standard specimen of 4mm thick. The strength of thicker specimen (4 mm) is less compared to thinner (3mm and 2mm) specimens. The loss in strength due to fatigue loading varies with thickness of specimens, depends on the stiffness of the specimens. This complicates the transfer of mechanical properties from small scale specimen testing to use in the design of large scale structures. The stiffness increases in ply level scaled specimens and decreases in sublaminate level scaled specimens with addition of Nanoclay compared to pure epoxy matrix. The reduction in residual strength is same for different thicknesses of scaled nano-composite specimens. There is a potential in reducing scaling effects in composites with the addition of Nanoclay in matrix. Copyright © 2013 by ASME.