PSI - Issue 40

S.A. Bochkareva et al. / Procedia Structural Integrity 40 (2022) 61–69 Bochkareva S. A., Panin S. V. / Structural Integrity Procedia 00 (2019) 000 – 000

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The level of stresses corresponded to the PEEK yield point of 105 MPa, while the one of delamination strains was equal to its fracture strain value of 10%. Analysis of theses surfaces and the corresponding relief images (Figure 4) enabled to conclude that the greatest stresses and strains were at the beginning and at the end of contact due to macro-bending of the plates. For a more detailed analysis, an enlarged part of the computational domain of the ‘PEEK - PEEK’ welded joint after tension is shown in Figure 5, a. The scale was increased mostly over the vertical direction along the Y axis. As a result, the fact that delamination initiated at the beginning and at the end of the contact was emphasized. In addition to macro-bending, the sample exhibited a slight micro-bending in the weld region.

Fig. 5 – An enlarged part of the computational domain of the ‘PEEK - PEEK’ welded j oint after tension (a) and the relief image of the elastic modulus surface (b) Figure 5, b shows a relief image of the elastic modulus surface, where the level lines emphasize areas of the fracture initiation: at the beginning of the contact layer on the bottom plate and at its end on the top one. In the case when the rigid interlayer in the ‘PEEK -PEEK prepreg/USW- PEEK’ welded lap joint was presented, the highest stresses were inside it, while the greatest strains were at the edges of the contact (Figure 6). The plates were joined with the prepreg interlayer 200 µm thick, which possessed orthotropic properties Kosmachev et. el. (2021): the elastic modulus was 130 GPa in the longitudinal direction, while it was 9 GPa in the transverse one. Its ultimate strength was 2900 GPa and 40 MPa, respectively, and elongation was 2% in the longitudinal direction and 5% in the transverse one. An image of a part of the computational domain in the ‘PEEK -PEEK prepreg/USW- PEEK’ welded joint is shown in Figure 6. In contrast to the previous case (Figure 5, a), micro-bending in the joint area was not observed, since the interlayer was stiffer than the plates.