Effects of waviness in composite materials

Abstract

This work is first approach study of the effects of fiber waviness on the elastic properties, specially the Young’s Modulus, of Laminate Composite Materials. This study has been carried out at the Institute for Aircraft Design (Intitut für Fleugzeugbau) of the University of Stuttgart (Universität Stuttgart) in Germany under the supervision of Dr. Anthony K. Pickett. The study involved work in three main areas: analytical, Finite Elements Analysis (FEA) and experimental. The analytical analysis has been developed from the studies carried out by H.M. Hsiao and I.M. Daniel from the Northwestern University in Evanston, Illinois, USA, in which they establish a complete and a simplified calculus procedure for different waviness types. In this work, the complete procedure was used. ([1] and [2]) The FEA analysis was carried out using the commercial code from ESI group. As only elastic properties were tested, no delamination on failure models were developed. The experimental analysis included the manufacturing of suitable laminate specimens of carbon fiber. Compression tests until first ply failure were also carried out in order to state the variation of elastic properties for a given relation of wave amplitude and wavelength.