Issue 46

C. Bellini et alii, Frattura ed Integrità Strutturale, 46 (2018) 319-331; DOI: 10.3221/IGF-ESIS.46.29 329 common threshold in the aeronautic field, coupled to undesired resin and fibre content, was found. It was also noted that near these points, immediately outside the Teflon ® sheet, there was a greater presence of resin, which formed a step as visible in Fig. 12. Figure 10 : Depth modification by Teflon ® sheets in the intersection points. After this preliminary optimization step, the new experimental testing campaign confirmed the improvement of the structural characteristics of the produced parts, even if the material quality in the transition zones between the nodes and the single ribs was still scarce. Therefore, the application of more advanced design tools, as FEM simulation, was necessary to attain the required quality level of the structure. Figure 11 : Defect absence in the circumferential head trajectory. Figure 12 : Detail that highlights areas with lower compaction. Specimen Resin content [%] Fibre content [%] Void content [%] Average St. Dev. CoV Average St. Dev. CoV Average St. Dev. CoV 1 37.24 1.34 3.60% 59.82 1.27 2.12% 2.94 0.07 2.54% 2 38.47 1.59 4.13% 58.76 1.35 2.30% 2.77 0.06 2.33% 3 37.82 1.27 3.36% 59.35 1.24 2.09% 2.83 0.07 2.39% 4 38.53 1.65 4.28% 58.37 1.43 2.45% 3.10 0.07 2.15% 5 36.62 1.17 3.19% 59.53 1.36 2.28% 3.85 0.09 2.36% 6 47.35 2.37 5.01% 38.64 2.45 6.34% 14.01 0.69 4.92% Table 6: Calcination test results after preliminary process design optimization.