Computational tool for fatigue analysis in composite material
Ricardo De Medeiros1; Giovani Sacchetto Daniel1; Marcelo Leite Ribeiro1; Volnei Tita1
1 Department of Aeronautical Engineering, São Carlos School of Engineering - University of São Paulo
doi:10.20906/CPS/COB-2015-0525
Resumo
The failure of composite laminates under fatigue loading is usually characterized by a combination of various damage modes such as delamination, matrix cracking, debonding, ply failure, and fiber breakage. These damage modes have been known to cause changes in material properties such as the residual strength, stiffness and life. Thus, it is possible to obtain a measure of the damage in composite laminates by measuring the changes in these properties. The mechanics of fatigue failure of laminated composite materials are completely different from that of conventional materials. The mechanics of fatigue failure of conventional materials involve the initiation and propagation of a single crack, which causes the material to fail. Laminated composite material can arrest the propagating crack to within a single lamina, thus avoiding immediate failure. Only after accumulation of cracks the laminate fails. The fatigue life of the laminate is best described by S-N curves. Unlike conventional materials, in which failure occurs due to a single crack, in composite materials there is a process of accumulation of many cracks. Therefore, fatigue life is expressed by loading history and residual strength is determined subsequently by the load which will cause eventual failure. Given the aforementioned context, the present study aimed to develop a computational tool that was able to consistently predict both the fatigue life of composite structures like the residual strength of these structures under the action of cyclic loads. Thus, a model based on the residual resistance, which involves numerical integration, is implemented in a computer program called Safecom (System of Fatigue Analysis in Composite Structures), which is evaluated for five case studies from literature: laminate without notch, laminate with micro-cracks, laminate with notch circular under compression and laminate with notch circular under tension. It is possible to conclude that there is a great convergence between the predicted results by computational tool a
Palavras-chave: Composite material; Damage tolerance; Residual strength; Fatigue