Purpose This paper aims to investigate the structural behaviour of polylactic acid (PLA) parts fabricated by fused deposition modelling (FDM) to support the development of analytical and numerical models to predict the structural performance of FDM components and categories of similar additive manufactured parts. Design/methodology/approach A new methodology based on uniaxial tensile tests of filaments and FDM specimens, infill measurement and normalization of the results is proposed and implemented. A total of 396 specimens made of PLA were evaluated by using variable process parameters. Findings The infill and the build orientation have a large influence on the elastic modulus and ultimate tensile stress, whereas the layer thickness and the infill pattern have a low influence on these properties. The elongation at break is not influenced by the process parameters except by the build orientation. Furthermore, the infill values measured on the test specimens differ from the nominal values provided by the system. Research limitations/implications The analysis of the structural properties of FDM samples is limited to uniaxial loading conditions. Practical implications The obtained results are valuable for the structural analysis and numerical simulation of FDM components and for potential studies using machine learning techniques to predict the structural response of FDM parts. Originality/value A new experimental methodology that considers the measurement of the real infill percentage and the normalization of the results for inter-comparison with other studies is proposed. Moreover, a new set of experimental results of FDM-PLA parts is presented and extends the existing results in the literature.
Purpose The purpose of this study is to evaluate the capability and performance of analytical models to predict the structural mechanical behaviour of parts fabricated by fused deposition modelling (FDM). Design/methodology/approach A total of eight existing and newly proposed analytical models, tailored to satisfy the structural behaviour of FDM parts, are evaluated in terms of their capability to predict the ultimate tensile stress (UTS) and the elastic modulus (E) of parts made of polylactic acid (PLA) by the FDM process. This evaluation is made by comparing the structural properties predicted by these models with the experimental results obtained from tensile tests on FDM specimens fabricated with variable infill percentage, perimeter layers and build orientation. Findings Some analytical models are able to predict with high accuracy (prediction errors smaller than 5%) the structural behaviour of FDM and categories of similar additive manufactured parts. The most accurate model is Gibson’s and Ashby, followed by the efficiency model and the two new proposed exponential and variant Duckworth models. Research limitations/implications The study has been limited to uniaxial loading conditions along three different build orientations. Practical implications The structural properties of FDM parts can be predicted by analytical models based on the process parameters and material properties. Product engineers can use these models during the design for the additive manufacturing process. Originality/value Existing methods to estimate the structural properties of FDM parts are based on experimental tests; however, such methods are time-consuming and costly. In this work, the use of analytical models to predict the structural properties of FDM parts is proposed and evaluated.
The prediction of the structural performance of additive manufacturing (AM) parts has become one of the main challenges to boost the use of AM in industry. The structural properties of AM are very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. While AM experimental studies are common in the literature, a limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches, such as the finite element method (FEM); however, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication. In this paper, the analysis and numerical simulation of the structural performance of fused deposition modeling (FDM) samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and polylactic acid (PLA) material. These samples were measured and modeled in a computer-aided design (CAD) system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally, the experimental and numerical results were compared and conclusions drawn.
The prediction of the mechanical properties of AM parts is very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. A limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches such as the Finite Element Method (FEM); nevertheless, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication. In this paper the analysis and numerical simulation of the mechanical performance of FDM samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and PLA material. These samples were measured and modelled in a CAD system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally the experimental and numerical results were compared and conclusions drawn.
Purpose The purpose of this study is twofold: firstly, to investigate the effect of the infill value and build orientation on the fatigue behaviour of polylactic acid (PLA) specimens made by fused filament fabrication (FFF), also known as fused deposition modelling; and secondly, to model the fatigue behaviour of PLA specimens made by FFF and similar additive manufactured parts. Design/methodology/approach A new methodology based on filament characterisation, infill measuring, axial fatigue testing and fatigue strength normalisation is proposed and implemented. Sixty fatigue FFF specimens made of PLA were fabricated and evaluated using variable infill percentage and build orientation. On the other hand, fatigue modelling is based on the normalised stress amplitude and the fatigue life in terms of number of cycles. In addition, a probabilistic model was developed to predict the fatigue strength and life of FFF components. Findings The infill percentage and build orientation have a great influence on the fatigue behaviour of FFF components. The larger the infill percentage, the greater the fatigue strength and life. Regarding the build orientation, the specimens in the up-right orientation showed a much smaller fatigue strength and life than the specimens in the flat and on-edge orientations. Regarding the fatigue behaviour modelling, the proposed Weibull model can predict with an acceptable reliability the stress-life performance of PLA-FFF components. Research limitations/implications This study has been limited to axial fatigue loading conditions along three different build orientations and only one type of material. Practical implications The results of this study are valuable to predict the fatigue behaviour of FFF parts that will work under variable loading conditions. The proposed model can help designers and manufacturer to reduce the need of experimental tests when designing and fabricating FFF components for fatigue conditions. Originality/value A fatigue study based on a novel experimental methodology that considers the variation of the FFF process parameters, the measurement of the real infill value and the normalisation of the results to be comparable with other studies is proposed. Furthermore, a new fatigue model able to predict the stress-life fatigue behaviour of PLA-FFF components considering variable process parameters is also proposed.
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