Resistência de laminados com furo aberto considerando incertezas nas propriedades admissíveis do material

Abstract

Laminates NCF (non-crimp fabrics) are the union of unidirectional layers through stitching threads. Those laminates gained visibility for structural applications due to its superior post-impact properties, greater speed of production and greater freedom for the orientation of the fibers. Newest techniques made it possible to manufacture lamina of reduced thickness and with a lower degree of undulation of fiber tows, achieving better resistance and thinner laminates. In this work the mechanical properties of NCFs are discussed as well as the mechanical behavior in cases of traction and compression. The stitching thread that holds the lamina stable is responsible for generating tension concentration regions. The fabrication methods significantly affect the final properties of NCFs, which brings attention the development of processes with less impact on the properties of the final structure. In this work, NCF panels with open holes of three distinct diameter sizes are analyzed through the finite element method. Progressive damage routines is applied, through the failure criteria of maximum allowable stress and Tsai-Wu, to determine the final failure of the laminate. The results obtained are compared with the experimental values found in literature. The sensitivity of these failure criteria according to the diameter of the hole was also evaluated. As the material properties values possess dispersion, it was also conducted an analysis of influence of these uncertainties on the ultimate resistance of the laminate.