Mechanical Properties, Structure and Fracture Behavior of Additive Manufactured FFF-ABS Specimens

Abstract

The Fused Filament Fabrication (FFF) method is one of the most important additive manufacturing (AM) technologies. This technology is used today with various kinds of thermoplastic materials, including ABS. The present study deals with the flexural strength and axial deflection of ABS specimens versus relative density, to observe the influence of build-orientations, build model and microscopic level defects of these properties. In this study, the mechanical and structural characterization of AM-FFF ABS material was studied by CAD modelling of different orientations, three point bending mechanical testing, visual testing, and multifocal light microscopy observation, including fractography analysis. To that end, three different standard building orientations (Flat, On Edge and Upright) were printed, and each was built in two different angle orientations (-45o/+45o and 0°/90o). Based on the three point bending testing results, it was found that the specimen with the highest flexural strength was not necessarily the one with the highest deflection. It was also observed that On Edge 0/+90o orientations showed a relatively larger flexural strength difference in comparison to other building orientations (Flat and Upright). When the mechanical properties achieved from a bending test next to the building platform were compared to the properties far from the building platform, only a slight difference was found, which means that the flexural strength difference results from the building strategy and it is not related to the specific bending surface. Based on fractography observation, there is a major difference in the mechanical properties and fracture surface appearance, when the samples are bent between the layers (Upright orientation) or when the samples are bent through the layers (Flat and On Edge orientation).

Structure and Fracture Visualization of Tilted ABS Specimens Processed via Fused Filament Fabrication Additive Manufacturing

“…properties of the tilted FFF-ABS specimens (Fig.3), where  r (%) is the relative density,  (mm) is the axial deflection, and  (MPa) is the flexural strength properties. The properties of the 90° (upright) specimens were reported by Gewelber et al (2020)[3] …”

“…The chosen 3D-printed specimen is a simple rectangular beam with specified geometry and dimensions according to ASTM D790 and ISO 178. The properties of the 90° (upright) specimens used in the current paper are taken from our previous ongoing study as reported by Gewelber et al ( 2020) [3]. The specimens were produced using the solid mode filling mode with a single outer raster line defining the layer's perimeter; each layer is composed of individual raster lines whose orientation varies between the layer at -45°/+45° (crisscross) according to the print strategy; the crisscross strategy is the most frequently employed as the default raster pattern in most FFF extruders.…”

“…Contact pressure is a critical determinant of the bond strength; higher contact pressures leading to larger contact surface area, provide improved mechanical properties. This study is part of ongoing research [3], [16]- [17], seeking to advance knowledge about the mechanical properties, structure, and fracture behavior of FFF-ABS parts by using a three-point flexural test method. The main reason for choosing the three-point flexural bend method over a four-point test method is that the maximum flexural stress appears under the loading nose in this method, while the maximum bend stress is spread over the section of the specimen between the loading points in the four-point bend tests.…”

Mechanical Performance, Structure and Fractography of ABS Manufactured by the Fused Filament Fabrication Additive Manufacturing

“…Fused filament fabrication (FFF) is a commonly used additive manufacturing (AM) process, based on extrusion and mainly applied in rapid prototyping [1] - [11]. With the development of advanced materials and technology, the AM-FFF technique is shifting from manufacturing prototypes to the production of industrial end products.…”

“…With the development of advanced materials and technology, the AM-FFF technique is shifting from manufacturing prototypes to the production of industrial end products. Mechanical properties need to be studied in detail to further bring the FFF technique into volume production in order to fabricate functional parts for new applications in many sectors of biomedical engineering, aerospace, civil engineering, and robotics [1] - [10]. For example, in the automotive industry, the AM-FFF method is used to print fixtures and jigs as well as prototypes for testing [2].…”