18 Investigation of Flexural Progressive …
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The purpose of the 3rd loading is to observe the damage evolution of the specimen
after the failure point. It can be found that although the load does not continue to
increase, the AE accumulated counts of the specimen still maintains an increasing
trend. In addition, the amplitude signal distribution of the AE is more concentrated,
and a large number of signals higher than 80 dB and even close to 100 dB appear.
This phenomenon may be attributed to the fact that the previous two times loadings
caused damage to the specimen mainly due to the fibers and matrix of the interface,
while the internal axis yarn and the braided yarn does not completely break, which
also reveal why the composites do not lose its bearing capacity immediately even
after reaching the failure point. However, the last loading may cause the yarn to break
and pull out, resulting in more and higher amplitude AE signals.
Figure 18.4 describes the distribution of AE amplitude and frequency varying
with the duration of the composite samples. The responds of the AE signals at
different loading stages can be seen from Fig. 18.4a–c, respectively. The frequency
and duration of AE signals are related to the damage type of materials, while the
Fig. 18.4 AE amplitude and frequency with increasing duration for specimen in 1st load (a), 2nd
load (b), 3rd load (c)
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The purpose of the 3rd loading is to observe the damage evolution of the specimen
after the failure point. It can be found that although the load does not continue to
increase, the AE accumulated counts of the specimen still maintains an increasing
trend. In addition, the amplitude signal distribution of the AE is more concentrated,
and a large number of signals higher than 80 dB and even close to 100 dB appear.
This phenomenon may be attributed to the fact that the previous two times loadings
caused damage to the specimen mainly due to the fibers and matrix of the interface,
while the internal axis yarn and the braided yarn does not completely break, which
also reveal why the composites do not lose its bearing capacity immediately even
after reaching the failure point. However, the last loading may cause the yarn to break
and pull out, resulting in more and higher amplitude AE signals.
Figure 18.4 describes the distribution of AE amplitude and frequency varying
with the duration of the composite samples. The responds of the AE signals at
different loading stages can be seen from Fig. 18.4a–c, respectively. The frequency
and duration of AE signals are related to the damage type of materials, while the
Fig. 18.4 AE amplitude and frequency with increasing duration for specimen in 1st load (a), 2nd
load (b), 3rd load (c)