Issue 60

A. Elakhras et alii, Frattura ed Integrità Strutturale, 60 (2022) 73-88; DOI: 10.3221/IGF-ESIS.60.06

mouth displacement. Also, modulus of elasticity can be obtained from the load-CMOD curve for notched for FD FRC specimens as follow[2,21,24]:     0 2 6 i L a V E C d b (7)

0.66

  

2

3

(8)

   0.76 2.28 3.87 2.04   





V





2





1

Ci is the initial compliance calculated from the load-CMOD curve, and V( α ) is the geometry factor. It is worth noting that the apparent flexural modulus of orthotropic laminates can be calculated by the Chord or Secant method recommended by ASTM D7264/D7264M [39]. On the other hand, Eqns. (7,8) were previously adopted to estimate the modulus of elasticity of FRC [21,24]and FGC [2]. Therefore, the modulus of elasticity was calculated for FRC and FGC specimens using Eqns. (7,8). Eqn. (7) calculated the modulus of elasticity for FD FRC as an apparent value to the whole composite layered FGC beams. To calculate a representative E, especially for FGC specimens, notched FGC specimens with relative notch depth ( α o =1/6) were tested for this study, as the FD of bottom layer for MC-FGC with α o =1/3 was fully cracked.

R ESULTS AND D ISCUSSION

Flexural behavior of MC-specimens he results of flexural strength for MC-FD FRC, and MC-FGC specimens at first crack initiation and maximum stress for specimens with different sizes and L/d ratios equal 4, 5, and 6 are given in Tab. 2.

T

Specimens

MC-FD FRC

MC-FGC

fl f at Maximum stress, MPa

at first cracking, MPa

at Maximum stress, MPa

L/d ratio

b×d×L, mm

Beam Code

B4-1 B4-2 B4-3 B5-1 B5-2

4 4 4 5 5 6

150×150×600 150×187.5×750 150×225×900 150×150×750 150×180×900 150×150×900

3.17 2.79 2.60 2.57 2.90 2.74

3.70 3.78 3.23 3.34 3.34 2.84

2.75 3.18 2.58 3.04 2.65 2.62

B6

E, GPa

27.00

33.30

Table 2: Results of flexural strength of MC-FD FRC and FGC specimens.

Fig. 4 shows stress-CMOD curves of MC-FD FRC and MC-FGC specimens with different sizes and span- depth ratios equal four, five, and six. The regulation factor was calculated for the tested specimens according to the suggested multi- linear mean curve. The suggested multi-linear mean curve was calculated based on average points of stress and CMOD at each observed variation on the curve slope for the four specimens in each case. For clear observation of the points at first cracking and maximum stress, the mean curves of MC-FD FRC and MC-FGC specimens were re-drawn up to CMOD equals 5 mm, as shown in Fig. 5.

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