47


 The four-point bending test fixture is placed in an insulated container and LN2 is

filled up slowly. The LN2 boiling disappears when the temperature of the test fixture

becomes stable. During experiment, LN2 is continuously added into the container so that

specimen is completely submerged since LN2 vaporizes due to the heat loss to

atmosphere. The four-point bending test is performed following the previous procedure

for room temperature tests.


Casel (Mid-layer thickness= 1 8 mm)


 Displacement (m)

Figure 3-16. Load-displacement curves from four-point bending tests at cryogenic
 temperature for the Specimen 1


Case 2 (Mid-layer thickness = 2 4 mm)


0002 0004 0006
 Displacement (m)


0008


Figure 3-17. Load-displacement curves from four-point bending tests at cryogenic
 temperature for the Specimen 2