Strength test of sandwich composite structure and fatigue life study of typical bolted joints

Objectives In the application of sandwich composite materials in ship structures, to ensure the structural strength characteristics, bolt connections are usually used between the sandwich composite structure and steel main hull. However, due to local stress concentration around the holes and the boundary effects at the connection locations, the bolt connection position is often becomes the most critical area of the structure, necessitating strength and fatigue assessments.

Methods For a full-scale steel-sandwich composite panel structure, the strength characteristics of the plate frame under a 0.1 MPa uniform load are studied using experimental and finite element methods. The accuracy of the finite element method is then verified by comparing its results with those from the experimental method. Subsequently, based on the finite element method, fatigue tests for two equivalent bolted joints are designed through structural stress equivalence, and the fatigue life of the steel-sandwich composite structure is evaluated and verified.

Results It is determined that the fatigue life of the panel structure under the design load meets the design requirement of 5 million cycles.

Conclusions Regarding the fatigue problem of large bolted connections, equivalent joints can be designed for fatigue testing, and load equivalence can be achieved through structural stress equivalence.