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Fabrication and testing of composite sandwich structures with load-tailored lattice cores
Motivated by the potential to increase the performance of composite lattice core (CLC) sandwich structures through load-tailored core topologies, the goal of this thesis is to fabricate and experimentally characterize optimized CLC sandwich structures for multi-axial load cases.
Background: Composite lattice structures are gaining increasing interest for use as core material in ultra-lightweight sandwich applications. The inherent stretch-dominated behavior of the lattice core allows them to reach structural performances superior than state-of-the-art core materials (e.g. honeycombs, foams). At CMASLab, ultra-lightweight lattice core sandwich structures made from carbon fiber reinforced thermoplastics are currently being developed and assessed for their use in aerospace.
Motivation: While periodic lattice cores (e.g. pyramidal) are ideal for withstanding uniaxial load cases (compression, shear), ongoing studies have shown that the performance of these sandwich structures under multi-axial load cases with non-uniform loads distribution (e.g. 3-point-bending, indentation) can be substantially increased by tailoring the arrangement and orientation of the lattice members in the core (i.e. the topology) to the particular load case (c.f. figure). At CMASLab, an optimization framework is currently established allowing to identify such optimum core topologies for mult-axial load cases under consideration of manufacturing constraints.
Background: Composite lattice structures are gaining increasing interest for use as core material in ultra-lightweight sandwich applications. The inherent stretch-dominated behavior of the lattice core allows them to reach structural performances superior than state-of-the-art core materials (e.g. honeycombs, foams). At CMASLab, ultra-lightweight lattice core sandwich structures made from carbon fiber reinforced thermoplastics are currently being developed and assessed for their use in aerospace.
Motivation: While periodic lattice cores (e.g. pyramidal) are ideal for withstanding uniaxial load cases (compression, shear), ongoing studies have shown that the performance of these sandwich structures under multi-axial load cases with non-uniform loads distribution (e.g. 3-point-bending, indentation) can be substantially increased by tailoring the arrangement and orientation of the lattice members in the core (i.e. the topology) to the particular load case (c.f. figure). At CMASLab, an optimization framework is currently established allowing to identify such optimum core topologies for mult-axial load cases under consideration of manufacturing constraints.
The objective of this thesis is to fabricate and experimentally characterize composite sandwich structures with optimized core topologies for multi-axial load cases. The major tasks are:
• Familiarization with an existing numerical framework for core topology optimization of composite lattice core sandwich structures & Identification of optimum structural designs for the load case under consideration • Manufacturing of the optimized structures using a semi-automated thermoplastic spot-welding process developed at CMASLab • Experimental testing of the fabricated composite lattice core sandwich panels according to test standards • Comparison of the performance of the tested sandwich structures with numerical predictions and assessment of the achieved performance increase with respect to structures with non-optimum lattice cores.
The objective of this thesis is to fabricate and experimentally characterize composite sandwich structures with optimized core topologies for multi-axial load cases. The major tasks are: • Familiarization with an existing numerical framework for core topology optimization of composite lattice core sandwich structures & Identification of optimum structural designs for the load case under consideration • Manufacturing of the optimized structures using a semi-automated thermoplastic spot-welding process developed at CMASLab • Experimental testing of the fabricated composite lattice core sandwich panels according to test standards • Comparison of the performance of the tested sandwich structures with numerical predictions and assessment of the achieved performance increase with respect to structures with non-optimum lattice cores.
Christoph Karl
PhD Candidate
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 PhD Candidate ETH Zurich - Laboratory of Composite Materials and Adaptive Structures Leonhardstr. 21, LEE O225 8092 Zurich, Switzerland