AEROFRACTURE ANALYSIS ON UNIDIRECTIONAL COMPOSITE PLATE BY MEANS OF FINITE ELEMENT METHOD AND DOUBLET LATTICE METHOD

• Main Author: Akmal Ramadhan, Faisal
• Format: Theses
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/84459
• Institution: Institut Teknologi Bandung

In the recent decades, composite materials have become key element to construct advanced structure, i.e., aircraft structure. The present work is aimed to provide insight on how fiber orientation and crack existence in dynamic characteristics and aeroelastic instability. A plate-like wing made of unidirectional composite is investigated. Different fiber orientations and configuration with various crack lengths and locations are observed. Modal analyses to obtain the dynamic characteristics, i.e., mode shapes and natural frequencies, are conducted by means of Finite Element Method (FEM). The Modal Assurance Criteria (MAC) is used to quantitatively evaluate the similarity of the mode shapes for different fiber orientations. In addition, the aeroleastic analysis conducted trough the implementation of P-K Method. The dynamic characteristics represented with the MAC results depict that the order of the first six vibration modes, i.e., bending and torsion modes, does not altered by the change of orientation. However, the fiber orientation does affect the value of natural frequencies. Furthermore, the existence of crack could reduce the natural frequencies significantly. Based on the MAC evaluation, as the crack length increases, the order of the mode shapes change and the natural frequency of a particular mode decreases. For the fundamental modes, first bending and torsion, the natural frequencies decrease by as much as 20% as the crack located near the root. For higher order modes, i.e., second and third bending, the natural frequencies decrease the most when the crack located near the antinode of the respective mode. Based on these results, there is very likely that coupling of two or more modes occur as the frequencies become closer. This argument fortified with the results obtained from the aeroelastic analysis. The change of fiber orientation affects the value of divergence and critical flutter speed. There are several orientations that experienced increase or decrease relative to the undamaged model. Furthermore, similar to the dynamic characteristics results, the variation of crack location does not affect the divergence nor flutter speed whereas the crack length does.