RESUMO O presente trabalho aborda a determinação das constantes elásticas efetivas de materiais compósitos estruturais de uso aeronáutico por meio de ensaio de vibração. O experimento foi conduzido em um aparato apropriado com interferômetro a laser. Inicialmente, foi realizado um ensaio de vibração do tipo livre para obtenção das frequências naturais intrínsecas à placa de compósito híbrido de alumínio aeronáutico com tecido prepreg de fibra de carbono/epóxi (CARALL). Do mesmo modo, verificou-se por meio deste método, o alumínio 2024 T3 que é uma liga metálica que pode ser aplicada em aeronaves. Tanto o alumínio quanto os compósitos foram modelados em aplicativo computacional (ANSYS) onde por meio do método de elementos finitos obtiveram-se frequências relacionadas aos seis primeiros modos de vibração. O alumínio aeronáutico apresentou uma maior precisão entre os materiais analisados em relação as suas frequências naturais. Em relação as constantes elásticas, a liga de alumínio 2024 T3 apresentou um módulo E1 de 71,3 GPa e um coeficiente de Poisson de 0,31. As constantes elásticas do CARALL foram determinadas como solução de um problema de otimização computacional descrita em linguagem própria contida em uma sub-rotina do ANSYS. Observou-se que o módulo de elasticidade principal e o coeficiente de Poisson são próximos dos valores encontrados numericamente pela regra da mistura (70 GPa e 0.3, respectivamente).

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).

Fiber-metal laminates (FML) composed of alternating layers of unidirectional fiber-reinforced plastic (FRP) laminae and aluminum-alloy sheets offer some superior mechanical properties, compared with either conventional laminates consisting of only FRP laminae or high-strength monolithic aluminum alloys. The environmental factors can limit the applications of composites by deteriorating the mechanical properties during service. Usually, polymeric matrix absorbs moisture when exposed to humid environments and metals are prone to surface corrosion. On the other hand, FML laminates presents more resistance of moisture when compared with their constituents. Evaluation of shear properties is particularly important in the design of mechanically fastened parts and components, which are subject to parallel and opposing loads. In this work, the shear behavior was studied for Glare laminates and its constituents in dry and wet conditions.