Structural optimization methods leading to variable stiffness laminates have high potential for improving the mechanical properties of a structure. Besides fiber laying techniques, an attractive possibility for manufacturing variable stiffness composite structures is a so-called patched laminate. In a patched laminate a layer does not necessarily consist of a single piece of fabric, but is assembled from a (high) number of fiber patches. This segmentation of a laminated structure into patches results in the following advantages and disadvantages:
+ possibility to tailor the laminate according to the local load state
+ superior mechanical properties compared to constant stiffness laminates
+ reduction or recycling of preform cutoffs
+ cost reduction
-reduction of mechanical properties due to interrupted fibers
- increased modeling complexity
Although having several advantages, the patched lami-nates approach poses the problem of their numerical modeling. Due to the discontinuous fibers and the magnitude of overlaps, classic modeling approaches fail. Therefore, a 2D shear lag calculation method was developed. In order to properly exploit the potential of the shear lag approach, a method for the automated creation of patched laminates simulation models has to be developed.
Structural optimization methods leading to variable stiffness laminates have high potential for improving the mechanical properties of a structure. Besides fiber laying techniques, an attractive possibility for manufacturing variable stiffness composite structures is a so-called patched laminate. In a patched laminate a layer does not necessarily consist of a single piece of fabric, but is assembled from a (high) number of fiber patches. This segmentation of a laminated structure into patches results in the following advantages and disadvantages: + possibility to tailor the laminate according to the local load state + superior mechanical properties compared to constant stiffness laminates + reduction or recycling of preform cutoffs + cost reduction
-reduction of mechanical properties due to interrupted fibers - increased modeling complexity
Although having several advantages, the patched lami-nates approach poses the problem of their numerical modeling. Due to the discontinuous fibers and the magnitude of overlaps, classic modeling approaches fail. Therefore, a 2D shear lag calculation method was developed. In order to properly exploit the potential of the shear lag approach, a method for the automated creation of patched laminates simulation models has to be developed.
• Literature research on graph theory and boundary representation models
• Development of a graph representation concept for patched laminates
• Development of a routine for determination of model domains and boundaries
• Development of a routine for the automated application of mechanical model and boundaries
• Development of a demonstrator structure
• Experimental validation of simulation
• Literature research on graph theory and boundary representation models • Development of a graph representation concept for patched laminates • Development of a routine for determination of model domains and boundaries • Development of a routine for the automated application of mechanical model and boundaries • Development of a demonstrator structure • Experimental validation of simulation
ETH Zürich
Ralph Kussmaul
LEE O 224
Leonhardstrasse 21
8092 Zürich
Phone: +41 44 632 37 50
kralph@ethz.ch
www.structures.ethz.ch
ETH Zürich Ralph Kussmaul LEE O 224 Leonhardstrasse 21 8092 Zürich Phone: +41 44 632 37 50