PSI - Issue 42

Stefan Sieberer et al. / Procedia Structural Integrity 42 (2022) 72–79

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S. Sieberer et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 8. Fractured Specimens 1 and 3.

Fig. 9. Side view of cracks of Specimens 1 (top) and 3 (bottom).

3.2. Fracture of Specimens

The specimens all fractured in the net cross-section perpendicular to the load application in fibre failure. There is no indication of bearing stress induced failure. Figure 8 shows fracture lines of Specimens 1 and 3, respectively. The crack from the static failure extends through the specimen as shown in Figure 9. The load-strain plots shown above indicate that there is linear behaviour until before fracture of the specimens. This shows that the CCF trajectories around the eye are designed to purpose and the load is carried by the fibres. Assuming that in this case stress and strain concentration factors are exchangeable, the rupture stress of the composite R m , c can be calculated as R m , c = K eye F A CCF (4) In this case, the composite strength for Specimens 2 and 3 with lower φ is the same with R m , c , l = 216MPa, and for Specimen 1 with higher fibre volume fraction φ , the value is R m , c , h = 360MPa. Correcting for the fibre volume fraction gives an estimate of the fibre stress at break with

R m , c φ 0

(5)

R m , f =

The approximately calculated fibre strengths for lower and higher φ are R m , f , l = 800MPa, and R m , f , h = 972MPa, respec tively. These values are lower than the manufacturer data for fibres under tensile test conditions, but are comparable to similar structures printed with di ff erent fibre and matrix material (Savandaiah et al. (2022b)).

4. Conclusions

This study has compared the static behaviour of an additively manufactured (AM) lug part with continuous carbon fibre (CCF) reinforcement. The e ff ect of fibre volume fraction φ is highly significant, with a small increase in φ