Objectives
- Produce preliminary design guidelines and assessment approaches for the use of additively manufactured (AM) lattices in structural parts based on a combined modelling and experimental approach.
- Characterise and quantify the statistical deviations of the as-built lattices from their ideal representations using microfocus X-ray computed tomography (XCT) scanning.
- Develop a robust modelling and analytical approach that captures the inherent statistical deviations and allows for determination of design factors for static and fatigue performance.
- Undertake a design-of-experiments (DoE) study for the static properties and fatigue behaviour of lattices.
- Validate the design rules on a representative demonstrator part.
Project Outline
Modelling
Following a review of the state-of-the-art of models and typical geometric imperfections in AM lattices, the most appropriate models for the prediction of the mechanical performances will be implemented. The effect of the geometric imperfections will be incorporated in the model by means of statistics in order to predict the performances of the material accurately. The models will be calibrated and validated using test data from the project, and will be used for the development of design guidelines and models for the use of lattice structures in mechanical components.
Production of Samples
Hundreds of samples will be manufactured based on a DoE plan in order to guarantee a robust characterisation of the mechanical performance. The samples will consider different lattice types, sizes and densities, and will be produced using at least two different laser powder bed fusion machines.
Characterisation and Testing
XCT scanning will be undertaken to quantify the geometric imperfections, including struts off-axis measurement, strut waviness, strut diameter and material accumulation at nodes. The XCT measurements will be used to provide probability distributions of non-ideal geometric features as a function of not just the unit cell design, but also the orientation of the struts. DoEs will be undertaken to design the mechanical tests. The mechanical tests will include at least compression to failure to generate their effective stress-strain curves, and fatigue loading conditions (cyclic compression or tension).
Demonstrator Part Validation
The combined numerical modelling and test programmes will be used to generate design guidelines, including safety factors, for the use of lattices in parts. These will be validated on a representative component, including a curved region with different lattice structures and densities to test the ability of the modelling guidelines to predict and accurately capture realistic-parts, not just flat arrays.
Relevant Industry Sectors
Benefits to Industry
The project will develop state-of-the-art modelling and model validation capabilities for use by industry. This will enable technology transfer, and more rapid qualification of novel components. The knowledge gained through a fundamental statistical examination of different components will help inform material and process selection for industry enabling robust and confident design.
The project will provide a methodology for application to other unit cell designs and materials; the lessons-learned through the DoE will enable more highly-optimised and efficient studies to be undertaken.
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