The Relationship of Buckle Pattern Change and Vibration Mode Shifting: Thermal Postbuckling and Vibration of Composite Laminates

The thermal postbuckling and free vibration behaviors of composite laminates were simultaneously investigated using the finite element method. Due to the uneven thermal expansion in the two principal material directions, the buckling mode of the plate may change from one pattern to another in the postbuckling region. Because of this buckle pattern change, the sequence of natural frequencies of the plate is also suddenly altered. By examining the local minimum of total potential energy of each buckling mode, thermal induced in-plane forces, and mode shapes, a clear picture of buckle pattern change and vibration mode shifting is obtained and the relationship between the buckling mode and fundamental natural mode is further clarified. The temperature gradient effect is also discussed in detail.