Guest lecture: Analysis of Skin/Stiffener Separation
18 september 2017 12:45 - Locatie: Lecture Room H, FACULTY OF AEROSPACE ENGINEERING, KLUYVERWEG 1, DELFT
Carlos G Dávila, NASA Langley Research Center, MS190, Hampton, USA, Carlos.G.Davila@nasa.gov
Summary: Skin/stiffener separation is the most common mode of failure in stiffened composite structures and it remains extremely challenging to predict. In the last 15 years, several powerful analysis tools and non-destructive inspection techniques have emerged that provide a much greater understanding of the initiation and propagation of delaminations. However, test results show that separation failure in co-cured skin/stiffener interfaces is much more complex than a delamination: separation is characterized by dense networks of interacting cracks and crack path migrations. These crack networks result in measurable large-scale and sub-ply-scale R curve toughening mechanisms, such as fiber bridging, crack migration and blunting, and crack delving, that are not present in standard material characterization tests for delamination. Consequently, a number of unknown issues exist regarding the level of analysis detail that is required for sufficient predictive fidelity. The objective of the present paper is to examine some of the difficulties associated with modeling separation failure in stiffened composite structures.
Short Bio: Carlos Dávila is a Senior Aerospace Research Engineer in the Structural Mechanics and Concepts Branch at NASA Langley Research Center in Hampton, Virginia. He obtained his Ph.D. degree in Aerospace Engineering in 1991 from the Virginia Polytechnic Institute. Upon graduation, he went to work at NASA Langley, first as a National Research Council Associate, then as an employee at the Vehicle Technology Directorate of the Army Research Laboratory, and finally as a NASA Civil Servant.
His research interests include the development of finite element methods for the prediction of damage propagation and residual strength of composite structures. He is the recipient of the NASA Exceptional Technical Achievement Medal for his work on damage models for composite materials..