PSI - Issue 28

James Allum et al. / Procedia Structural Integrity 28 (2020) 591–601 J.Allum et al. / Structural Integrity Procedia 00 (2019) 000–000

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eighteen specimens utilised for mechanical characterisation. The final specimen dimensions were (H) 45 mm x (W) 5 mm, with a gauge thickness of 0.5 mm, defined by the extruded-filament thickness in the gauge. All specimens were cut using the same protocol and were dimensionally the same, with the only difference between the types being the orientation of their extruded filaments. F specimens were divided into two groups of six specimens. One F group received no further processing and were designated F NG (Fig. 2 (a)). The other F group were scored transversally using a surgical blade at five equidistant regions of the gauge section on both the front and back faces of the specimens to generate manual grooves (Fig. 2 (b)); these specimens were designated F G . Consistency in the cut was ensured by using only the weight of the blade to generate downward pressure when scoring. Six specimens were manufactured in the Z direction (Fig. 2 (c)). All specimens were stored in bags with silica desiccant to reduce any possibility of moisture absorption.

Fig. 2. A schematic diagram of an F specimen (a) and a Z specimen (b) - cut from their respective boxes. Dashed lines denote the contours of the test specimen with respect to the box from which they are cut. The cross-sectional close up schematic of each specimen type demonstrates the variation in extruded filament orientation of the F (a) and Z (b) specimen, which can also be seen in the dogbone cross-section.

Fig. 3. A schematic of each specimen type with a cross-sectional close-up showing the filament-scale geometric features. The FNG specimen (a) has extruded filaments aligned longitudinally and no visible transverse features in the cross-sectional view. The FG specimen (b) has five equidistant manually applied transverse grooves on each face (one set of which are shown in detail on the cross-sectional close-up), which mimic those naturally present in the Z specimen (c), shown in detail in the cross-sectional close-up. Filament orientation is indicated for each specimen type.