Residual strength criterion based on damage metric and Flexural After Impact (FAI) test for composite materials
Ricardo de Medeiros1; Murilo Sartorato1; Sandra Patricia da Silva Tita2; Dirk Vandepitte3; Marcelo Leite Ribeiro1; Volnei Tita1
1 Department of Aeronautical Engineering, São Carlos School of Engineering - University of São Paulo; 2 Department of Materials Engineering, São Carlos School of Engineering - University of São Paulo; 3 Department of Mechanical Engineering - PMA, KU Leuven
doi:10.20906/CPS/COB-2015-0524
Resumo
Composite materials have been utilized for nearly four decades owing to their beneficial characteristics, such as stability, weight and high stiffness. Particularly, in the aerospace industry the use of composites is justified by reducing structural weight with consequent fuel saving and improving performance. During the service life, a composite structure is subjected to various loading conditions, which can give rise to various defects. Composite laminates are especially sensitive to low velocity impacts since even minor damage can cause considerable reduction in structural integrity. Also laminated composite materials are susceptible to damage by out-of-plane impact, often associated with a corresponding reduction of mechanical properties. In fact, the impact energy is absorbed through remarkable internal damage mechanisms without exterior signs detectable by visual inspection. Various types of damages, like delamination, fiber-breakage, matrix cracking and fiber-matrix interfacial debonding can occur, leading to structural failure. To ensure that a damaged structure will not catastrophically fail during service life and will maintain maximum structural efficiency, it is necessary to carry out damage tolerance studies, evaluating the residual properties of the structure after impact. This study present a new criterion to evaluate the residual strength of laminate composite subject to low velocity impact loading. One of the objectives of this research was to investigate the feasibility of an elastic flexural test as an effective metric for the residual properties of an impacted composite. For this, a flexure after impact (FAI) test will be used alongside the standard CAI to compare its practicality as a damage tolerance technique. Low-velocity impact tests and residual strength tests are performed using an instrumented drop-weight machine and static test machine, respectively. The experiments were carried out on laboratory specimens, which are flat and rectangular composite plates. Two different stacking sequen
Palavras-chave: Flexure After Impact (FAI); composite laminates; experimental analyses; residual strength; impact testing