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Reduction of Edge Effects in Composite Lattice Core Sandwich Structures through Topology Optimization
The objective of this thesis is to study the reduction of edge effects in composite lattice core sandwich structures by optimizing the topology
of the lattice core, in order to increase the global structural performance under out-of-plane compression loading.
Background: Owing to their high specific strength and stiffness characteristics, composite lattice structures, comprising a repeating unit cell of pyramidally arranged composite rods, have recently gained increasing interest for use as low-density core material in ultra-lightweight sandwich applications. As the lattice members deform predominantly in stretchning and compression upon application of an external load, these structures can reach superior specific performance than state of the art core materials such as honeycombs and foams.
Motivation: The performance of composite lattice cores (stiffness, strength) is commonly characterized considering a representative unit cell with infinite boundaries, yielding uniform stresses throughout the core. In real applications, however, the physical boundaries of the sandwich structure induce a non-uniform stress distribution near the edges (known as edge effects), which are a cause for reduced structural performance. By optimizing the topology of the lattice core, a stress homogenization and thus reduced edge effects can be achieved, allowing to increase the strength and stiffness of the structure.
Background: Owing to their high specific strength and stiffness characteristics, composite lattice structures, comprising a repeating unit cell of pyramidally arranged composite rods, have recently gained increasing interest for use as low-density core material in ultra-lightweight sandwich applications. As the lattice members deform predominantly in stretchning and compression upon application of an external load, these structures can reach superior specific performance than state of the art core materials such as honeycombs and foams.
Motivation: The performance of composite lattice cores (stiffness, strength) is commonly characterized considering a representative unit cell with infinite boundaries, yielding uniform stresses throughout the core. In real applications, however, the physical boundaries of the sandwich structure induce a non-uniform stress distribution near the edges (known as edge effects), which are a cause for reduced structural performance. By optimizing the topology of the lattice core, a stress homogenization and thus reduced edge effects can be achieved, allowing to increase the strength and stiffness of the structure.
The objective of this thesis is to reduce edge effects in composite lattice core sandwich structures through topology optimization of the lattice core, in order to increase their performance under out-of-plane compression loading. The major tasks are: • Familiarization with an existing parametrized FE model for pyramidal lattice core sandwich structures • Investigation of edge effects in pyramidal lattice core sandwich structures through parametric FEA. • Establish an optimization framework enabling numerical topology optimization of the lattice core • Carry out numerical optimizations of the core topology to reduce the edge effects and homogenize the core stresses; Compare the performance increase with respect
to the periodic (non-optimized) structure
The objective of this thesis is to reduce edge effects in composite lattice core sandwich structures through topology optimization of the lattice core, in order to increase their performance under out-of-plane compression loading. The major tasks are: • Familiarization with an existing parametrized FE model for pyramidal lattice core sandwich structures • Investigation of edge effects in pyramidal lattice core sandwich structures through parametric FEA. • Establish an optimization framework enabling numerical topology optimization of the lattice core • Carry out numerical optimizations of the core topology to reduce the edge effects and homogenize the core stresses; Compare the performance increase with respect to the periodic (non-optimized) structure
Christoph Karl
ETH Zurich - Laboratory of Composite Materials and Adaptive Structures
Leonhardstr. 21, LEE O225
8092 Zurich, Switzerland
tel: +41 44 632 0840
email: karlc@ethz.ch
Christoph Karl
ETH Zurich - Laboratory of Composite Materials and Adaptive Structures Leonhardstr. 21, LEE O225 8092 Zurich, Switzerland