Development of an in-panel attachment method for fiber-placed composite lattice and grid-stiffened structures

Abstract

Composite grid-stiffened and lattice structures have been the focus of an increasing amount of research over the past decades, mainly because of their excellent structural performance. Most of the previous and current research focuses on analysis, manufacturing, and optimization of the base structure. Although more and more is becoming known about grid structures, methods for introducing loads mid-panel are scarce. With some applications requiring hundreds of attachment points, the potential impact of the attachment points is significant. Therefore, development of an efficient attachment method can allow grid structures to be used in an increasing number of applications. Recognizing the state of the art, a new concept for in-panel attachments is developed, which adds a laminate patch between the ribs of the structure to allow traditional fastening methods to be used. To analyze this concept, a rapid analysis method is constructed which makes use of several analytical methods and a fully parametrized finite element model to predict the strength of the attachment point. The feasibility of the concept and the used analysis method are validated by destructive testing of multiple test samples, and correlating the obtained data to the model. Resulting from the observations, several improvements are made to the model. Although some issues in the base structure are identified in the process, the feasibility of the novel attachment method is shown.