A Lean Method for Local Patch Reinforcement Using Principal Stress Lines

Abstract

Composite materials offer the possibility to design tailored laminates for a broad spectrum of applications such as airplane wings or monocoques in the automotive industry. Especially when carbon fiber reinforced plastic is used, parts with enormous performance can be designed. The downside of designing a laminate is the complexity of the task itself, as well as the price of the carbon fiber. Placing the expensive carbon fiber only at the necessary positions can help to reduce the costs of the parts and to increase the performance, specifically the stiffness, compared to a glass fiber laminate itself. Designing the laminate gets even harder, an algorithm is needed to support the engineer in this task.

This paper will introduce a lean method using the principal stress line to locate the best position for carbon fiber patches using a Michell structure. The Michell structure is optimized for tensile and pressure forces. Unidirectional tapes have outstanding properties in fiber direction, but weak performance orthogonal to the direction of the fiber. Placing the unidirectional tapes along the Michell structure will load the tapes in an optimal way. First of all the algorithm will determine the principal stress lines connecting load and bearing. These will be used as a starting point for a Michell structure. The generated Michell structure will be optimized to increase the performance. After the substructure is found, it will be mapped back into the original laminate. The new improved laminate will be compared with the original one, concerning weight, stiffness and pricing. A significant reduction in weight could be achieved at a constant price and improved stiffness.