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Abstract: 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. [Copyright &y& Elsevier]

Abstract: The paper addresses the problem of sandwich beams/panels with junctions between different core materials. The physics of the impairing local effects induced by a mismatch of the elastic material properties at core junctions is discussed, and the results of an experimental investigation concerning the quasi-static failure behavior of sandwich beams with conventional butt and “structurally graded” core junctions is discussed. The term “structurally graded” core junctions include scarf junctions and junctions provided with local reinforcing patches of the faces. The influence of the junction interface geometry on the quasi-static deformation, failure initiation and crack patterns are studied experimentally for sandwich beams loaded in the three-point bending. It is shown that “structurally graded” core junctions perform better than conventional butt junctions, and thus improve the strength of the structure. [Copyright &y& Elsevier]

Abstract: This paper presents a simple analytical model for the prediction of thermo-elastic deformation (spring-in) of angled composite sandwich panels. The development of the model is presented and the simplifying assumptions are clearly defined. Contributions from different mechanisms are clearly shown which gives a good understanding of the problem. The analytical model is validated against a finite element model and the validity of the simplifying assumptions is examined. The agreement between predicted spring-in from the analytical model and the finite element model is very good for the studied sandwich panels with composite skins and varying core materials. The difference in spring-in predictions is less than 0.05° for all cases studied. The simplicity of the model together with the limited number of input parameters makes it a practical tool for composite manufacturing engineers and designers. [Copyright &y& Elsevier]