## 3 Results
### Impact Test  
In Figures 3-5 are plotted the energy-displacement mean curves for the untreated and aged specimens of the T300/EP Composite, the sandwich with Kraibon SUT and the sandwich with Kraibon HHZ. The error bars are useful to understand the reliability of the tests. The first graph compares the performance of the three configurations at 6 m/s. The following two graphs underline the velocity and aging effect on each damping material applied. The averaged results with the standard deviation of the impact tests are reported in the Table 4.  
In Figure 3, aged and not-aged impact performance of samples was illustrated. A distinct difference between the two types of reinforces can be noted. SUT maintains and slightly improves the performance of the reference material. On the other hand, HHZ layer reduces the energy absorbing properties of the composite structure. While in the first part of the impact test (until 15 mm of displacement), HHZ absorbed more energy respect to T300 and SUT samples, it failed at 20 mm of displacement prematurely by fragile rupture. Both these features can be explained by HHZ higher Young's modulus with respect to T300 and SUT. Figure 4: Energy-displacement mean curves for untreated or aged specimens of sandwich with Kraibon HHZ. Figure 3: Energy-displacement mean curves for untreated and aged specimens of T300/EP composite. Similar tendencies are obtained as a result of aging. HHZ samples at 6 m/s, during an initial energy absorption phase, performed as the 1.5 m/s tested samples aged. There is therefore a similar effect between the increase in speed and the absorption of humidity. At 6 m/s aged instead there is an overlap of the effects (velocity and moisture) with a drastic lowering of absorbed energy. As can be seen in Figure 5, in the SUT samples, the overlapping of the effects is less marked in the initial phase of the test, since the 6 m/s AGED curve overlaps with the untreated and 1.5 m/s AGED curves. However, the comparison between the effect of speed and aging is exclusive to the first phase of energy absorption and does not continue for whole test. The variation in the values of peak force and energy are summarized in Table 5. The following considerations can be proposed:  
1. Damping layers effect: The absolute values of peak force and energy at 6 m/s for untreated sandwich laminates were divided per the values of untreated composites. This value permits to consider the increment due to the integration of damping layer in the sandwich structure for the untreated condition;
2. Aging effect: The values of peak force and energy at 6 m/s for the aged materials were divided per the values of untreated respective configuration. This value permits to consider the effect of the aging for each material respect to the untreated condition;
3. Velocity effect: The ratio between the energy at 6 m/s and the energy at 1.5 m/s was found for aged and untreated specimens. This value permits to consider the variation of energy absorption at the two velocities for the untreated and aged conditions. It was evaluated that this calculation is not so effective for the peak force, due to the poor reliability of the maximum peaks in the load-displacement graphs.