Comparison of Analytical and Experimental Natural Frequencies of a Composite Beam

When it comes to composite materials, a fundamental difference arises from the isotropic materials, contrary to the latter case, the stratified nature of composites inevitably generates anisotropy in the structural behavior of the laminates. Instead of two independent variables as for steel or aluminum, glass-reinforced plastic (GRP) requires at least five independent variables, that are calculated upon micromechanics assumptions. This article evaluates the accuracy of a method based on the Classical Laminate Theory to calculate the equivalent laminate properties in computing the natural frequencies of structures in GRP yachts. Natural frequencies are evaluated beforehand with the results of the beam theory, subsequently, Experimental Modal Analysis (EMA) is conducted to validate the analytical results, being a benchmark for comparison. The study aims to assess the validity of a laminate equivalent mechanical properties method when used to determine the natural frequencies, reducing the time needed in the preprocessing phase of most common FEM software.