FATIGUE OF FOAM CORE SANDWICH BEAMS .1. UNDAMAGED SPECIMENS

The present paper addresses the fatigue characteristics of two cellula r foam core materials as used in load carrying sandwich structures. Th e fatigue loading studied is a constant shear stress which corresponds to the main type of loading that the core in a sandwich structure exh ibits. Based on results from testing stress-life curves are presented for a number of stress ratios (R) and are fitted to a simple two-param eter Weibull function. The influence of the R-value is emphasized and standard Haigh diagrams are constructed. It is seen that the fatigue b ehaviour of the core materials investigated herein well can be describ ed in manners similar to that of classical metal fatigue. A thorough i nvestigation is performed on the behaviour of fatigue crack formation and growth. (C) 1997 Elsevier Science Ltd.