PSI - Issue 34

H. Oberlercher et al. / Procedia Structural Integrity 34 (2021) 111–120 Hannes Oberlercher/ Structural Integrity Procedia 00 (2019) 000 – 000 7 6 and Figure 7. The three test runs with different layer heights show also an irregularity in the microstructure. Sample (a) shows a higher percentage of voids in the composite compared to the sample with the same layer height with the MF consolidation printing technology. The fibre distribution in the matrix is also well distributed in all samples. However, it turns out that by increasing the pressure with the consolidation unit, a smoother and more even top and bottom surface could be produced. 117

Figure 6:Single line samples of the 3DCP.

Figure 7 shows a two-layer laminate with seven lines. In a first test with the same process parameters as the MF 3D printer, the same problem as described in chapter 3.2.1 appears. The seven lines in the layer are good contacted but especially between the layers there are more cavities. It is obvious that not enough heat is supplied to the joining zone so that the substrate reaches the melting temperature and fuses with the printed filament. In order to generate more heat in the matrix material, the printing speed was reduced. Sample (c) with the lowest printing speed about 5 mm/s shows a homogeneous laminate with a good monolithic structure between the lines and layers (See Figure 7 (c)).

Figure 7: Seven lines with two layers with different printing speed.

3.3 MF CFC 3-printer bending test results The study showed a stepwise improvement of bending strength about 50% as well as an improvement of the flexural