**5. Conclusions**

Considering the conditions applied in the evaluation of pins deposited by CMT PIN process in FMLPs, the following conclusions are listed according to the type of testing.

Non-destructive evaluation:

• By means of the four natural frequency modes obtained after the modal analysis, the presence of the pins in the FMLPs did not result in a significant stiffness increase. There are, in this case, probably two factors acting in opposite directions; the pins would lead to an increase in stiffness due to the anchoring action between metal and composite, but on the other hand the mass increase with more pins inside the panels is a stiffness-reducing factor as in any structure. However, the presence of the pins in the FMLPs significantly increased the damping factor, dissipating the applied vibration wave. Pin deposition was able to reduce the propagation of vibrations at low frequencies (from 0 to 800 Hz) by up to about five times (for some resonance modes).

• CMT PIN process, through its thermo-mechanical working principle, changes the surface profile of the metal sheets on the opposite face in the region of deposition, but only on a microscopic scale. In addition, thermoxidation occurs in these regions, which is not a problem because this inconvenience could be avoided/minimized by the application of purge gas (supplementary protection to that used near the electric arc and inert).

Destructive evaluation:

**Figure 26.** Average results obtained through five measurements of maximum load, displacement at maximum load and

a better union, consequently showing better results. Possibly, failures in pinned specimens would be less catastrophic after reaching the maximum load (after failure), which should be

Considering the conditions applied in the evaluation of pins deposited by CMT PIN process

• By means of the four natural frequency modes obtained after the modal analysis, the presence of the pins in the FMLPs did not result in a significant stiffness increase. There are, in this case, probably two factors acting in opposite directions; the pins would lead to an increase in stiffness due to the anchoring action between metal and composite, but on the other hand the mass increase with more pins inside the panels is a stiffness-reducing factor as in any structure. However, the presence of the pins in the FMLPs significantly increased the damping factor, dissipating the applied vibration wave. Pin deposition was able to reduce the propagation of vibrations at low frequencies (from 0 to 800 Hz) by up to about

in FMLPs, the following conclusions are listed according to the type of testing.

maximum shear stress of the Iosipescu shear test.

exploited in future work.

Non-destructive evaluation:

five times (for some resonance modes).

**5. Conclusions**

116 Optimum Composite Structures

