PSI - Issue 13

Emre Özaslan et al. / Procedia Structural Integrity 13 (2018) 535–541 M.A. Güler et al./ Structural Integrity Procedia 00 (2018) 000 – 000

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specimens which had same specimen width to hole diameter ratio, but different sizes were tested to investigate the size effect. Finite element analysis was performed to determine stress concentration factor and to predict the strength for all specimen configurations. 2. Experiment The material used in this study is “MTP H 510 CFA 200 12 UD RC42” carbon/epoxy composite. All tests were executed with INSTRON universal test machine that has 100 kN load capacity. Five specimens were tested to obtain the repeatability for all specimen configurations. Firstly, material characterization tests were performed. The ply elastic properties were obtained using ASTM D 3039/D 3039M-00 and ASTM D 3518/3518M-94 standards and are presented in Table 1, where 1 E and 2 E are the ply longitudina l and transverse Young’s moduli respectively, 12 G is the ply shear modulus, and 12 v is the ply major Poisson’s ratio. The ply strength properties are listed in Table 2, where t X and t Y are the ply longitudinal and transverse tension strength respectively, c X and c Y are the ply longitudinal and transverse compressive strength respectively and S is the ply shear strength.

Table 1. Material properties of the carbon/epoxy material

Value ( MPa )

Material Property

1 E 2 E 12 v

100000

7400 0.32 3767

12 G

Table 2. Ply strength values of the carbon/epoxy material

Strength ( MPa )

Strength direction

t X c X

1200 -1500

t Y

23

c Y

-150

S

73

A test matrix was created to investigate the size effect phenomenon in composites that have circular holes. The specimen types are listed in Table 3 and geometrical dimensions are shown in Figure 1. The specimens OHT1 to OHT4 were tested to investigate the effect of specimen width (W) to hole diameter (D) ratio on the stress concentration and strength. The specimens OHT2, OHT5 and OHT6 were tested to examine the size effect on the stress concentration and strength. All specimens had same ply sequence that was 2 [45/90/-45/0] s . All specimens had a thickness of 4.16 mm. Video extensometer was used to collect strain data to compare finite element results and test results.

Fig. 1. Geometrical dimensions of the specimens