Fatigue performance of sandwich beams with a pyramidal core

Sandwich beams have been manufactured from AISI type 304 stainless steel faces and AL6XN pyramidal core, and subjected to both monotonic and cyclic three-point bending in order to assess their monotonic and cyclic strengths. Collapse mechanisms maps for monotonic loading, and fatigue maps for cyclic loading are constructed with the aid of simple analytical models for the competing failure modes. These maps serve as useful design guides, and take the sandwich beam geometry as axes. The construction of the maps takes as input independent measured values for the monotonic and cyclic strengths of the faces and of the pyramidal core. Good agreement is found between the predicted and observed failure modes and strengths for both the static and fatigue tests. In particular, S–N fatigue curves for core shear are obtained from single-lap shear tests and from three-point bending tests, and are in close agreement.