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Experimental investigation of mechanical stiffness in lattice structures fabricated with PLA using fused deposition modelling

Eljihad A., Nassraoui M., Bouksou O.

Journal of Achievements in Materials and Manufacturing Engineering

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2023

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Vol. 119, nr 2

60--71

EN

Purpose The objective of the paper is to design and characterise with polylactic acid (PLA) material three cellular structures in the form of lattices which are diagonal-octet-centred shapes for two sizes 6x6x6 and 12x12x12 with a compression test to examine their stiffness using FDM technology compared to polyjet technology. Design/methodology/approach The study used two analytical approaches to investigate lattice structures: experimental analysis and theoretical analysis. Experimental methods such as compression tests were conducted to determine the characteristics of lattice structures. In addition, theoretical analysis was conducted using Hook's law and Ashby's Gibson model to predict appropriate behaviour. The combination of experimental and theoretical methods provided a comprehensive understanding of lattice structures and their properties. Findings The experimental study examined the impact of the shape and size of a lattice structure on the stiffness and lightness of objects 3D printed with FDM technology by PLA material. The research revealed that the 6x6x6 diagonal lattice structure size provided a good balance between stiffness and lightness. While the 6x6x6 byte structure was even lighter, with a mass ratio of 2.09 compared to the diagonal structure, it was less rigid, with a ratio of 0.43, making the diagonal structure more suitable for certain applications. The study highlights the importance of considering both the shape and size of the lattice structure when designing 3D-printed objects with specific mechanical properties; the chosen structure could be a good choice for applications where stiffness and lightness are important. Research limitations/implications The limitations of the research lie in its limited scope, focusing primarily on the effect of shape (octet-diagonal centred) and unit cell size on Young's modulus of PLA material. Other aspects of 3D printing, such as material selection and thermal properties, were not considered. Furthermore, the results obtained are specific to the printing parameters and experimental conditions chosen, which limits their generalizability to other 3D printing configurations or methods. However, these results have important implications for optimising the PLA printing process. They enable the identification of optimal parameters, such as unit cell shape and size, to produce stiffer, higher-quality structures. In addition, the research is helping to improve the mechanical properties of 3D-printed lattice parts, paving the way for more efficient manufacturing methods and stronger components. Practical implications Our analysis can be used as a decision aid for the design of FDM lattice parts. Indeed, we can choose the diagonal structure of 6x6x6, which would provide favourable stiffness for functional parts. Originality/value The paper explores the compression test of lattice structures using FDM technology, which presents a new direction for additive manufacturing. The study takes an experimental approach to evaluate the reliability of various additive manufacturing technologies for creating lattice structures. The study results provide insight into the most reliable technology for producing lattice structures.

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Old materials – new capabilities: lattice materials in structural mechanics

Augustyniak M.

Journal of Theoretical and Applied Mechanics

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2018

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Vol. 56 nr 1

213--226

EN

Lattice materials (LM) are a novel concept stemming from the combination of crystallography and structural optimisation algorithms. Their practical applications have become real with the advent of versatile additive layer manufacturing (ALM) techniques and the development of dedicated CAD/CAE tools. This work critically reviews one of the major claims concerning LMs, namely their excellent stiffness-to-weight performance. First, a brief literature review of spatially uniform LMs is presented, focusing on specific strength of standard engineering materials as compared with novel structures. An original modelling and optimisation is carried out on a flat panel subject to combined shear and bending load. The calculated generalised specific stiffness is compared against reference values obtained for a uniform panel and the panel subjected to topological optimisation. The monomaterial, a spatially repetitive solution turns out to be poorly suited for stiff, lightweight designs, because of suboptimal material distribution. Spatially non-uniform and locally size-optimised structures perform better. However, its advantage over manufacturable, topologically-optimised conventional designs can at best be marginal (< 10%). Cubic-cell lattices cannot replace conventional bulk materials in the typical engineering use. The multi-cell-type and multi-material lattice structures, albeit beyond the scope of this article, are more promising from the point of view of mechanical properties. The possibility of approaching the linear scaling reported in the recent litterature can make them an attractive option in ultra-low weight designs.

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Zastosowanie optymalizacji topologicznej w kształtowaniu odlewanych konstrukcji szkieletowych

Piekło J., Pysz S., Małysza M.

Prace Instytutu Odlewnictwa

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2014

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T. 54, nr 4

77--87

PL

Konstrukcje szkieletowe są ważnym elementem stosowanym jako absorbery energii w przemyśle zbrojeniowym, lotniczym i samochodowym. Jednoczesne zastosowanie algorytmów optymalizacji topologicznej do kształtowania wytrzymałościowego, programów symulacji krzepnięcia, metod wytwarzania przyrostowego (AM – ang. additive manufacturing) oraz technologii sterujących procesami krzepnięcia, może mieć znaczący wpływ na otrzymanie konstrukcji lekkiej i wytrzymałej. Kształt takiej konstrukcji w sposób optymalny dopasowany jest do przenoszenia obciążeń przy określonym działaniu sił zewnętrznych i sposobach podparcia. Celem niniejszej pracy było przedstawienie możliwości, jakie dają wspólne zastosowanie metod optymalizacji topologicznej oraz metod przyrostowych wykonania oprzyrządowania odlewniczego do wykonania odlewów szkieletowych, odpornych na działanie sił ściskających.

EN

Cellular structures are critical components which perform as energy absorbers in the defense, aerospace and automotive industries. Simultaneous application of topological optimisation algorithms for strength forming, solidification simulation software, additive manufacturing (AM) methods and solidification process control technologies may have a significant impact on building lightweight and strong structures. The shape of such structures is optimally adapted for transmission of loads with certain action of external forces and bearing methods. The purpose of this paper is to present the potential released by joint application of topological optimisation methods and AM methods in building of casting equipment for production of cellular castings which can resist compressive forces.