## 2 Materials and Methods  
The reproductions of slamming impact were made with the equipment presented in Figure 2. It is composed of a variator-electric motor assembly coupled to a cam with a shaft supported by two flexible supports to dissipate the reaction energy of the cam when pressing the panel and protect the drive from possible excessive lateral loads. The cam is keyed while remaining fixed to the shaft and rotates between 200 to 320 RPM. The panel was installed at its base with gauge screws that allowed exerting pressures between 0 to 1200 kN/mm\({}^{2}\) and the panel is adjusted crosswise to the cam. A revolution counter was installed, and the temperature control was carried out with a thermal imager, to avoid that the temperature does not reach the glass transition temperature of the material due to friction. Two types of panels were made of GFRP, without viscoelastic layer which was called \"unmodified\" and with viscoelastic layer which was called \"modified\". Some were made from Gurit WE-91 triaxial (0\({}^{\circ}\)/45\({}^{\circ}\)/90\({}^{\circ}\)) pre-impregnated OoA (Out-of-Autoclave curing), cooled to -18 \({}^{\circ}\)C, vacuum cured. The panels were manufactured using 3 fabrics of 1 mm each, cut to 270 \(\times\) 270 mm corresponding to the  
Figure 1: Organization of the research presented. frame dimension of the test equipment. In the panels with the viscoelastic sheet, it was included after the first triaxial sheet. All the panels included a strain gauge at 40 mm from the impact zone. For the manufacture of the viscoelastic sheets, a printer was used with two independent extruders so that there is no contamination between the materials. They were printed on a thermal surface. For the manufacture of the outer capsule, 3 mm acrylonitrile butadiene styrene or ABS was used. A linear thermoplastic polyurethane or TPU was used for the inner elastomer. Figure 3 shows a generic viscoelastic layer. Depending on the manufacturing date for the experiments, the color type of the ABS varies, so there are black and blue. The curing process of the panels was with a vacuum pressure bag and in an oven at a temperature of 120 degrees Celsius for 90 min. This process was applied to unmodified panels as well as modified panels. A 12-m-long vessel constructed from GFRP was selected, and the maximum allowable slamming pressure values were calculated. This pressure occurs from the midsection towards the bow at the bottom of the ship. The purpose was to perform the slamming reproductions with lower values, in such a way that the failure of the material is due to propagation of the damage due to the cyclic load. The ABS classification rules for high-speed boats, Chapter 3, Section 2.2 [13] were used for the calculation. The ship's bottom pressures were calculated for the fully loaded condition, operating at maximum speed according to the selected geographic navigation area: The Galapagos Islands. Three-point bending tests were performed to experimentally determine the pressure threshold from which damage begins to occur on the unmodified material. Cured specimens were cut from a panel into strips 15 mm wide by 250 mm long. They were flexed beyond their elastic limit until the  
Figure 3: Generic viscoelastic layer. Figure 2: Reproduction equipment for slamming impacts. tension machine registers non-linearity, indicating the appearance of the first micro-cracks equivalent to the damage threshold as seen in Figure 4.  
A machine for vertical weight drop testing was built. The impactor carriage falls by gravity on two chrome rails to reduce the effect of friction. The panels to impact were installed at its base, with all its edges embedded. It has an anti-bounce system with a laser reader to control the number of impacts. It has an acceleration sensor or gravitometer installed that sends the information to a data acquisition system and tabulates the acceleration G-force versus the time of impact. The equipment has a frame-shaped structure to which all parts are secured.