Effect of the fibre length on the mechanical anisotropy of glass fibre–reinforced polymer composites printed by Multi Jet Fusion

Figures & data

Figure 1. MJF printing of GF/PA12 composites with bioinspired mechanical anisotropy.

Figure 2. SEM images (a–c) and length distributions (d–f) of Fibre-124, Fibre-226, and Fibre-271.

Figure 3. Avalanche angle distributions, median avalanche angles (A_m), and bulk densities (D_b) of Powder-124 (a), Powder-226 (b), and Powder-271 (c).

Figure 4. Thicknesses of different specimens prepared at layer thickness = 90 μm (a) and lamp speed = 16 inch/s (b).

Figure 5. Porosity of different specimens: layer thickness = 90 μm (a); lamp speed = 16 inch/s (b).

Figure 6. TGA (a) and DSC (b) curves of Specimen-271, Specimen 226, and Specimen-124.

Figure 7. Optical microscope images of polished X-Y, Y-Z, and X-Z planes in Specimen-124 (a–c), Specimen-226 (d–f), and Specimen-271 (g–i).

Figure 8. Fibre orientation in the polished X-Y planes of Specimen-124 (a), Specimen-226 (b), and Specimen-271 (c).

Figure 9. Simulated composite powder beds with different types of GFs: (a) Powder-124, (b) Powder-226, and (c) Powder-271 and the percentage of fibres orientated along the powder spreading direction within 20° versus the fibre length.

Figure 10. SEM images of the fractured surfaces of Specimen-124 (a–c), Specimen-226 (d–f), and Specimen-271(g–i) (the lamp speed = 16 inch/s; the layer thickness = 90 μm) in the Z-, X-, and Y- orientation.

Figure 11. Mechanical properties of different specimens (a, c, and e: layer thickness = 90 μm; b, d, and f: lamp speed = 16 inch/s) in the Y-orientation.

Table 1. Mechanical properties of different specimens (the layer thickness = 90 μm) in the Y-orientation.

Lamp speed (inch/s)		14	16	18	20
UTS (MPa)	Specimen-124	50.78 ± 0.57	54.43 ± 0.09	53.78 ± 0.84	55.62 ± 0.58
	Specimen-226	66.26 ± 0.46	67.31 ± 0.87	68.69 ± 0.44	65.35 ± 0.95
	Specimen-271	60.85 ± 0.27	62.78 ± 0.38	63.52 ± 0.38	63.80 ± 1.00
Tensile modulus (GPa)	Specimen-124	3.63 ± 0.08	4.07 ± 0.11	3.81 ± 0.35	3.90 ± 0.22
	Specimen-226	5.47 ± 0.33	5.84 ± 0.54	5.07 ± 0.42	4.53 ± 0.48
	Specimen-271	4.47 ± 0.98	4.31 ± 0.22	4.74 ± 0.46	4.14 ± 0.07
Elongation at break (%)	Specimen-124	5.58 ± 0.09	6.22 ± 0.31	5.54 ± 0.50	5.07 ± 0.36
	Specimen-226	3.32 ± 0.43	3.61 ± 0.23	3.99 ± 0.51	4.20 ± 0.39
	Specimen-271	3.55 ± 0.18	3.73 ± 0.37	3.28 ± 0.20	3.46 ± 0.42

Figure 12. Stress–strain curves (a–c), UTS (d), tensile modulus (e), and elongation at break (f) of Specimen-124, Specimen-226, and Specimen-271.

Table 2. Dependence of the mechanical properties of different specimens in the X- and Z-orientations (lamp speed = 16 inch/s; layer thickness = 90 μm).

Specimen		Specimen-124	Specimen-226	Specimen-271
UTS (MPa)	X-orientation	52.58 ± 0.09	48.24 ± 1.24	40.23 ± 1.28
	Z-orientation	51.43 ± 2.65	38.54 ± 2.70	29.57 ± 6.54
Tensile modulus (GPa)	X-orientation	3.67 ± 0.57	3.05 ± 0.23	2.46 ± 0.31
	Z-orientation	2.84 ± 0.22	2.53 ± 0.24	2.16 ± 0.19
Elongation at break (%)	X-orientation	7.42 ± 0.08	5.53 ± 0.33	5.81 ± 1.56
	Z-orientation	6.90 ± 1.33	5.19 ± 1.26	2.55 ± 0.41

Table 3. UTS and tensile modulus (in the powder spreading direction) of PA12-based specimens fabricated by SLS and MJF.

Material	Technique	Fraction (wt%)	Size	UTS (MPa)	Tensile modulus (GPa)	Source
PA12	SLS	0	–	45.10	1.72	(Salazar et al. 2014)
	MJF	0	–	44.5	1.37	(Cai et al. 2021)
GB/PA12	SLS	40	60 µm	29.30	2.43	(Cano, Salazar, and Rodríguez 2018)
	MJF	40	58 µm	30.0	2.3	(O’Connor and Dowling 2020)
CF/PA12	SLS	–	–	66.7	6.3	(Jansson and Pejryd 2016)
	SLS	30	7 µm (diameter)/150–250 µm (length)	80	5.80	(Jing et al. 2017)
AF/PA12	MJF	12	500 µm (length)	66.44	5.34	(Chen et al. 2022)
GF/PA12	SLS	25	200 µm (length)	43.70	2.71	(Salazar et al. 2014)
	MJF	20	11 µm (diameter)/122 µm (length)	48.3	4.02	(Liu et al. 2021)
	MJF	20	16 µm (diameter)/226 µm (length)	67.31	5.84	This work
	MJF	25	16 µm (diameter)/226 µm (length)	64.88	6.21	This work

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