Tensile strength of partially filled FFF printed parts: meta modelling. Issue 3 (18th April 2017)

• Record Type: Journal Article
• Authors: Mahmood, Shahrain; Qureshi, A.J.; Goh, Kheng Lim; Talamona, Didier
• Is Part Of: Rapid prototyping journal. Volume 23:Issue 3(2017)
• Page Start: 524
• Page End: 533
• Publication Date: 2017-04-18
• Subjects: Tensile strength -- Fused filament fabrication -- Additive manufacturing -- Meta modelling; Engineering design -- Periodicals; 620.004205
• DOI: 10.1108/RPJ-10-2015-0151
• Languages: English
• ISSNs: 1355-2546

Abstract

Abstract : Purpose: This paper aims to investigate the tensile strength of partially filled fused filament fabrication (FFF) printed parts with respect of cross-sectional geometry of partially filled test pieces. It was reported in the authors' earlier work that the ultimate tensile strength (UTS) is inversely proportional to the cross-sectional area of a specimen, whereas the number of shells and infill density are directly proportional to the UTS with all other parameters being held constant. Here, the authors present an in-depth evaluation of the phenomenon and a parametric model that can provide useful estimates of the UTS of the printed part by accounting for the dimensions of the solid floor/roof layers, shells and infills. Design/methodology/approach: It was found that partially filled FFF printed parts consist of hollow sections. Because of these voids, the conventional method of determining the UTS via the gross cross-sectional area given by A = b × h, where b and h are the width and thickness of the printed part, respectively, cannot be used. A mathematical model of a more accurate representation of the cross-sectional area of a partially filled part was formulated. Additionally, the model was extended to predict the dimensions as well as the lateral distortion of the respective features within a printed part using input values from the experimental data. Findings: The result from this investigation shows that to calculate the UTS of a partially filled FFF part, the calculation based on the conventional approach is not sufficient. A new meta-model is proposed which takes into account the geometry of the internal features to give an estimate of the strength of a partially filled printed part that is closer to the value of the strength of the material that is used for fabricating the part. Originality/value: This paper investigates the tensile strength of a partially filled FFF printed part. The results have shown that the tensile strength of a partially filled part can be similar to that of a solid part, at a lower cost: shorter printing time and lower material usage. By taking into account the geometries within a printed part, the cross-sectional area can be accurately represented. The mathematical model which was developed would aid end-users to predict the tensile strength for a given set of input values of the process parameters.