PSI - Issue 34

H. Oberlercher et al. / Procedia Structural Integrity 34 (2021) 111–120

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Hannes Oberlercher/ Structural Integrity Procedia 00 (2019) 000 – 000

modulus about 25% in 0° fiber direction (See Figure 8). Sample (d) has a bending modulus about 34 [GPa] and a bending strength about 343 [MPa].

Bending modulus 0° [GPa]

Bending strength 0° [MPa]

40

400

20

200

[GPa]

[MPa]

0

0

d

c

b

a

d

c

b

a

Figure 8: Bending properties in 0° fibre orientation with MF 3D-printer

The specimens with the 90° fiber direction showed only low differences to each other (See Figure 9). Sample (d) has a bending modulus about 1.4 [GPa] and a bending strength about 26 [MPa].

Bending modulus 90° [GPa]

Bending strength 90° [MPa]

0,00 10,00 20,00 30,00

2,00

1,00

[GPa]

[MPa]

0,00

d

c

b

a

d

c

b

a

Figure 9: Bending properties in 90° fibre orientation with MF 3D printer

The reduction of the layer height had a positive effect on the fiber distribution in the matrix and decrease the content of cavities in the composite (see Figure 4 (d)). The test sample with the lowest nozzle distance and the highest consolidation pressure, sample d – 0°/90° cross section in fiber direction, provided the best mechanical properties and the most homogeneous microstructure. Conclusion and Outlook The adopted process parameters have shown an improvement of the mechanical properties and the microstructure. Nevertheless, the layering of the MF 3D-printed CFC produces still cavities in the laminte, and the fibers are not homogeneously distributed in the matrix. This leads to a reduction of the mechanical properties. With a first approach of controlled 3DCP technology, a significant improvement of the fiber distribution and the bonding of the individual layers could be achieved. In this study, we have shown that consolidation in a broader sense is a joining process that depends on the material temperature and the consolidation time. The major goal is for the processed semi-finished products to be joint together and form a monolithic structure. This physical process leads to the formation of strength at the joint and can reduce imperfections to a high degree (Guglhör, 2017), (Ehrenstein, 2018). However, a need for further development of the 3D-printed consolidation process and the selection of the process parameters remains. In a further investigation, the detailed content of voids in the laminate as well as the distribution of the fibre matrix will be analysed. Furthermore, a consolidation model for predicting the void content in the 3D printing compound is to be developed, which will also specify the process parameters to be selected for the 3D-printer. With this strategy, an increase of the mechanical properties of the 3D printed composite should be achieved. 4