Mechanical Characterization of Solid Oxide Fuel Cells and Sealants

 
Data from 4-point bending test in this work used in the FEM simulation of creep.
 
Temperature (°C) 
E 
(GPa) 
[140]
Poisson’s ratio 
[140] 
 A 
(s
-1 
MPa
-n
)
 
n 
Q 
(kJ/mol) 
800 
29 
0.29 
5.7 × 10
-4
1.4
147 
4.3.4.
Bending strength 
Bending tests were performed using an electromechanical testing machine (Instron 1362). The 
central displacement was measured with a sensor attached to the tensile loaded sample surface. A 
ceramic extension rod connected to a linear variable differential transformer (Sangamo, LVDT, 
range ± 1 mm, precision 1.25 μm) provided the value of actual displacement. The load was 
measured with a 1.5 KN load cell (Interface 110 BLR). The testing set-up permitted 
measurement was carried out from room temperature up to 1000°C. In this work two different 
bending techniques have been used, four-point bending test and three-point bending test, with 
head-to-head and bar-shaped specimens, respectively.

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Experimental 
69 
4.3.1.1
Four-point bending test
Besides creep behavior, four-point bending tests were also carried out to characterize fracture 
stress, following the ASTM C1-161 standard. The particularly designed head-to-head specimens 
used in this work are described in section 4.1.2. The elastic modulus and corresponding stress of 
4-point bending can be expressed as: 
𝐸 =
3 ∙ ∆𝐹 ∙ 𝐿
3
16 ∙ 𝑏 ∙ ℎ
3
∙ ∆𝑓
(4-6) 
𝜎 =
3 ∙ 𝐹 ∙ 𝑚
𝑏 ∙ ℎ
2
(4-7) 
where 
ΔF
and 
Δf
are the force and deflection in the linear region of load-deflection curve, 
respectively. 
F
is the applied force, 
L
is the length between supporting rods, 
b
and 
h
is the 
specimen width and height, respectively. The elastic modulus is determined from the linear 
region of the load-deflection curve. The fracture stress is determined from the maximum applied 
load.
The four-point bending tested sealant specimens are listed in 
Table