Work Behavior Analysis Of Stiffened Composite Panels Based On Measured Strain Data

Experimental and numerical investigations of stiffened composite laminatedpanels have been conducted for many years. A method, treating finite elementanalysis as theoretical guidance, comparing with the measured strain data andexperimental phenomenon, has been developed. A large number of finite elementanalysis data and experimental data have been obtained. Furthermore, the bucklingload of experimental component could be indentified by analyzing theload-displancement curve of key measuring points. However, this analytical methodis traditional and simplex. The analysis of both finite element analysis andexperimental data is not enough. The data mining is still in the low level. And alsothe intrinsic relationship between the data and the characteristic of the structureimplicated in the data internally have not been revealed.Differing from the traditional analytical method, this dissertation proposes anew analytical method of performance for stiffened composite panels from the viewof energy based on the concept of structure stress state mode. The relationshipbetween generalized strain energy density (GSED) method and structure stress statemode of experimental component is also discussed. Thus, the best area ratio ofreinforced truss and skin among three types of panels is determined.Firstly, the GSED method is proposed, which can deal with large amounts ofstrain data. It is able to express the characteristics of the component’s performanceby summing the squares of normalized data.Secondly, quasi strain energy density (QSED) is defined based on the definitionof strain energy density (SED). On this basis and combining with experimentalphenomenon, the sensitivity analysis of each experimental component is completed.Moreover, the rate of component’s QSED changing with the load and thecharacteristics of the component’s performance when experimental load was largerthan buckling load is conducted.Finally, the concept of structure stress state mode is defined. The C-2typepanel is identified as the one has the best area ratio of reinforced truss and skinamong C-1, C-2and C-3three types of experimental components by analyzing theirstructure stress state mode.In conclusion, strain data becomes the bridge between the experimental loadand the characteristics of the component’s performance in the proposed GSEDmethod. And the new concept of structure stress state mode defined in thisdissertation can reveal the characteristics of the component’s performance in detailand visually. The research provides the new analytical theory for the further studies of structural experiment.