EXPERIMENTAL AND FINITE ELEMENT ANALYSIS FOR COMPOSITE AIRCRAFT STRUCTURES.

World over composite materials are being increasly employed in a variety of aerospace applications because of its inherent advantages. The present work examines both experimental and analytical (FE) analysis conducted on a composite wing box of an aerobatic aircraft. Results are referred in the form of gain, phase, and coherence for a selected number of locations on composite the wing box are further processes to yeild to the the main eigenvalues and eigenvectors. The natural frequencies and mode shapes of the wing box considered as the main dynamic characteristics are only given. The experimental investigations of the wing box are reviewed briefly in this paper. Representitive finite element models simulating the actual composite wing box are subsequently developed. The paper further looks in to the pertinent details relating to these developments and gives an approach used in establishing the final finite element model, employed for comparative study. The paper also discusses the finite element models generated, using MSC/PATRAN, and analyzed using the standard FE, MSC/NASTRAN software. Results from both of the above analysis are compared and discussed. It is shown how often, particularly in the case of composite structures, differences may arise in these comparisons. These differences are discussed and measures sought to identify and or eradicate the differences. The attemp at this stage, is to evaluate the magnitude and possible reasons for the differences and to seek measures to minimize them. Complexities of composite structures are well known as are the difficulties of attaining appropriate composite structure section properties. It is felt that the analytical (FE) model generated is true representitive of the real wing box.