PSI - Issue 2_B

Koji Fujimoto et al. / Procedia Structural Integrity 2 (2016) 182–189 Koji Fujimoto, Masahiro Hojo, Akira Fujita / Structural Integrity Procedia 00 (2016) 000 – 000

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out under the load-controlled condition of the sinusoidal loading with the frequency 1 Hz and the stress ratio 0.1 using a servo hydraulic dynamic test machine INSTRON 8500. The maximum load P max was set to be 63-75 % of the static tensile strength obtained by Hojo et al. (2013). The value of P max applied to each specimen is shown in Table 2. The corresponding maximum out-of-plane stress max r  calculated by Eq. (4) is also shown in the same table. Figure 1 (b) is an example of the images of the four-point-bending fatigue tests. After the fatigue test, each delaminated specimen was grinded off at the parts shown by the red diagonal lines in Fig. 2 and fracture surfaces were observed by a microscope.

w : Width of the L-shaped specimen in the z -direction (perpendicular to the x-y plane) r o : Outer radius of the curved section of the L-shaped specimen

P

L-shaped specimen

l t



D

r i

d x

y



d y

x

l b

t

P

(a) Schematics of the four-point-bending test specified by ASTM Designation: D 6415/D 6415M – 06a (2006).

(b) An image of the four-point-bending fatigue test using an L-shaped specimen.

Fig. 1. Experimental apparatus of the four-point-bending fatigue test.

Table 1. Dimensions of the experimental apparatus and the specimen. Variances in t , r i and r o are due to fabrication. l t l b D t r i r o w 75 mm 100 mm 9.5 mm 6.10 mm – 6.32 mm 6.08 mm – 6.20 mm 12.03 mm – 12.11 mm 25 mm

Table 2. Maximum load P max and the corresponding maximum out-of-plane stress max r  applied to each specimen. Specimen No. LS-1 LS-2 LS-3 LS-4 LS-5 P max 3.48 kN 3.52 kN 3.02 kN 3.20 kN 3.82 kN max r  75.6 MPa 76.4 MPa 68.0 MPa 70.4 MPa 80.8 MPa

Delamination (Fracture surface)

Fig. 2. The regions shown by the red diagonal lines were grinded off and the delaminated (fracture) surfaces were exposed for the observation.