## 5 Results
### Comparison between Cyclic and Dynamic Tests Results  
The reduced frequency range of the tension-compression and dynamic tests is different, as confirmed in Figures 10 and 11. The tension-compression tests cover a reduced frequency range between approximately 10\({}^{-7}\) Hz to 10\({}^{9}\) Hz at a reference temperature of 15 \({}^{\circ}\)C. The dynamic tests cover a reduced frequency range between approximately 1 Hz and 10\({}^{12}\) Hz at the same reference temperature of 15 \({}^{\circ}\)C. Therefore, the best fit between the two tests is expected to be for frequencies higher than 1 Hz and lower than 10\({}^{9}\) Hz for which experimental data from the two tests is available. As the two methods of back analysis of the dynamic tests give similar results, only the complex modulus obtained from the 2S2P1D model calibrated using the second method of analysis was chosen for the comparison with results of the 2S2P1D model calibrated from quasi-static tension-compression tests data. The relative difference between the norm (in %) and the phase (in \({}^{\circ}\)) of the complex modulus from the two calibration processes are plotted in Figure 14 where the results are plotted against the reduced frequency at 15 \({}^{\circ}\)C for all specimens. It is shown in Figure 14 that the complex modulus simulated from the two tests are in quite good agreement for the high reduced frequencies (>10\({}^{7}\) Hz), which was expected when dealing with dynamic measurements. The norm of the dynamic complex modulus is around 3-5% higher than the norm of the complex modulus of the tension-compression tests for this frequency range and there is less than 0.2\({}^{\circ}\) of difference between the phase angles from both tests. For lower reduced frequencies (or higher temperatures), the relative difference increases for the norm and reach a value between 12% and 30% at 1 Hz depending on the specimen with an average value of 20.2%. The difference also increases for the phase angle but remains less than 2.5\({}^{\circ}\) for reduced frequencies higher than 1 Hz. The differences observed in Figure 14 show that the dynamic complex modulus has a higher norm and a lower phase angle than the complex modulus obtained from the tension-compression tests. The differences between the two tests increase with temperature. These results are in agreement with results from previous studies using FRFs [18; 19; 20; 21]. The differences between the two tests could be due to two phenomena. First, the level of strain applied is different in the two types of tests (about 50 \(\upmu\)m/m for the tension-compression tests and about 0.1 \(\upmu\)m/m for the dynamic tests). It is known that AM have a nonlinear behaviour showing a strain level dependence even at small strain amplitude [39; 40; 41]. The differences observed in this analysis are in the same direction than the observed nonlinearity: increasing of norm and decreasing of phase angle when decreasing strain amplitude. Then, nonlinearity may account for at least a part of the difference between the two tests. Another possibility is ageing of the materials. The tension-compression tests were performed several months before the dynamic tests  
Figure 13: Difference between the complex modulus obtained from the two methods of analysis of the dynamic tests plotted at a reference temperature of 15 \({}^{\circ}\)C for all specimens: (**a**) relative difference for the norm of the complex modulus (in %); and (**b**) difference for the phase of the complex modulus (in \({}^{\circ}\)). and this could explain why the dynamic complex modulus is stiffer. However, the overall agreement between the two tests is satisfying. The shift factors from the WLF equation obtained from the tension-compression tests and from the dynamic tests are plotted in Figure 15. It is seen that, for the low temperatures, the agreement between the shift factors from both tests is very good.