Structurally graded core junctions in sandwich beams: fatigue loading conditions

Sandwich beams with inclusion of different core materials were the subject of the experimental study [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in sandwich beams: quasi-static analysis. Compos Struct, in press], which focused on the static performance of such sandwich elements. The concept of structurally graded core junctions, suggested in [Bozhevolnaya E, Thomsen OT. Structurally graded core junctions in sandwich beams: quasi-static analysis. Compos Struct, in press], presents different geometrical shapes of the core interfaces (e.g. bias junctions) as well as core junctions with locally reinforced faces. The novel design of core junctions was shown to provide larger critical static loads and more beneficial crack initiation and propagation patterns in sandwich beams. This paper is devoted to a comparative study of the performance of sandwich beams with conventional and structurally graded core junctions under fatigue loading conditions. An experimental investigation of the fatigue behaviour of the sandwich beams was performed using a three-point bending loading scheme. A rigorous statistical treatment of the experimental data has shown that structurally graded core junctions perform much better than conventional butt junctions. Thus, the fatigue life of the sandwich beams with structurally graded core junctions was up to 30% higher than the fatigue life of the sandwich beams with the conventional junction design.