Obtaining the effective elastic constants under dynamic condition of hybrid laminate for aeronautical use

ABSTRACT

This paper deals with the determination of the effective elastic constants of structural composite materials of aeronautical use by means of vibration test. The experiment was conducted in an appropriate apparatus with a laser interferometer. Initially, a free-vibration mode vibration test was performed to obtain the natural frequencies intrinsic to the hybrid composite plate (aeronautical aluminum lamina’s alternating to carbon fiber/epoxy fabric lamina’s) known as CARALL. Likewise, aluminum 2024 T3 which is a metallic alloy that can be applied in aircraft was verified by means of this method. Both the aeronautical aluminum and the hybrid composite were modeled in a computer application (ANSYS) where, through the finite element method, frequencies related to the first six modes of vibration were obtained. The aeronautical aluminum presented a greater precision between the materials analyzed in relation to their natural frequencies. Regarding the elastic constants, the 2024 T3 aluminum alloy presented an E₁ modulus of 71.3 GPa and a Poisson’s ratio of 0.31. The CARALL elastic constants were determined as the solution of a computational optimization problem described in its own language contained in an ANSYS subroutine. It was observed that the main modulus of elasticity and Poisson’s coefficient are close to the values found numerically by the mixing rule (70 GPa and 0.3, respectively).

Keywords
Hybrid composite; carbon fiber; vibration test; mechanical properties