## 3 Results and Discussion
### Influence of the Sensor Position
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Descriptor**} & \multicolumn{2}{c}{**Tensile Test on Composite Glass Fibres**} & \multicolumn{2}{c}{**Tensile Test on CMC Composite with \(\mu\)80**} \\  & \multicolumn{2}{c}{**and Vinylester Matrix with Two Kind of Sensors Located at P1 and P3 on the Surface**} \\  & \multicolumn{2}{c}{**Sensors (micro80 and picoHF)**} & \multicolumn{2}{c}{**of the Specimen**} \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ Rise Time (\(\mathrm{\SIUnitSymbolMicro}\)s) & Q1 & 7 & 6 & Q1 & 21 & 6 \\  & Median value & 12 & 11 & Median value & 33 & 15 \\  & Q2 & 18 & 15 & Q2 & 50 & 35 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ Amplitude (dB) & Q1 & 70 & 70 & Q1 & 50 & 57 \\  & Median value & 77 & 78 & Median value & 57 & 63 \\  & Q2 & 83 & 82 & Q2 & 63 & 72 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ Energy (Attojoule) & Q1 & 8352 & 6629 & Q1 & 150 & 550 \\  & Median value & 25,482 & 18,293 & Median value & 591 & 2857 \\  & Q2 & 77,260 & 40,380 & Q2 & 3424 & 13,962 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ Amplitude/average & Q1 & 0.44 & 0.32 & Q1 & 0.24 & 0.27 \\ Frequency & Median value & 0.56 & 0.39 & Median value & 0.27 & 0.30 \\  & Q2 & 0.68 & 0.47 & Q2 & 0.30 & 0.33 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ Rise angle (dB/\(\mathrm{\SIUnitSymbolMicro}\)s) & Q1 & 4.26 & 5.18 & Q1 & 0.96 & 1.9 \\  & Median value & 6.82 & 7.22 & Median value & 1.48 & 4.22 \\  & Q2 & 11 & 12 & Q2 & 2.20 & 7.78 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ FC (\(\mathrm{kHz}\)) & Q1 & 279 & 401 & Q1 & 230 & 316 \\  & Median value & 306 & 464 & Median value & 243 & 324 \\  & Q2 & 334 & 487 & Q2 & 254 & 358 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ PF (\(\mathrm{kHz}\)) & Q1 & 232 & 541 & Q1 & 150 & 318 \\  & Median value & 244 & 578 & Median value & 156 & 324 \\  & Q2 & 326 & 593 & Q2 & 205 & 336 \\ \hline  & Sensor & Micro80 & PicoHF & Sensor & Micro80 P1 & Micro80 P3 \\ Weighted & Q1 & 232 & 541 & Q1 & 190 & 318 \\ frequency (\(\mathrm{kHz}\)) & Median value & 286 & 516 & Median value & 201 & 323 \\  & Q2 & 313 & 536 & Q2 & 249 & 328 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Median values, the upper and the lower quartiles for several descriptors recorded during tensile test on composite glass fibres and vinylester matrix with two types of sensors located at the same place (micro80 and picoHF) and during tensile test on CMC composite with \(\mu\)80 sensors located at P1 and P3 on the surface of the specimen. Figure 9: _Cont._In order to compare the descriptors recorded directly on the specimen and at the extremities of the waveguide, a comparison of the data recorded by sensor located at P1 at the end of the waveguide and by sensor P3 at the surface is done. It has shown that 17 descriptors out of 25 have a relative difference greater than 25%. We also note that the rise time, the energy and the frequency mainly the peak frequency are greatly affected by propagation distance. These results show that is difficult to assign a damage mechanism to an AE signal only with the value of the frequency.