PSI - Issue 47

Jaroslav Václavík et al. / Procedia Structural Integrity 47 (2023) 282–289 Author name / Structural Integrity Procedia 00 (2019) 000–000

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  = ε i+1 - ε i x i+1 - x i ∙ t CFRP ∙ E CFRP

6

(4)

a) b) Fig. 5. a) Scheme of the position of strain gauges used for debonding criterion) and b) tested specimen

limit, below which no CFRP delamination occurred. The maximum sheer stress value from Fig. 6a) corresponds to the catalogue sheer strength of the adhesive.

Fig. 6 a) Distribution of normal CFRP stress, measured at the CFRP surface and sheer stress in the adhesive, evaluated using (4), b) S-N curve of basic steel sample compared with broken samples with CFRP plate and with points, evaluated from early CFRP delamination of 5 mm The results of the fatigue test are given in Fig. 6b). The evaluated S-N curve of basic steel material is plotted here including broken and unbroken samples and the tolerance limits for 95% probability. For the OSR broken or unbroken samples with any not defined delamination only points are plotted. It is obvious, that the life of the samples with CFRP plates is substantially higher in comparison with the steel samples. S-N curve for defined CFRP delamination of 5 mm however lies under the steel fatigue curve of about 10 %. 3.2. Fatigue tests on large structural node The structural node was selected from the car frame - a longitudinal beam with holes and a crossbar welded together (Fig. 7a) with the aim of reinforcing the beam with the CFRP plate from below or from both sides. The joint was manufactured from steel hollow profiles 100×60 mm with the thickness 3 mm. The structural node at the