• UFRJ Nautilus

Choosing Materials for the Structure of our AUV - Part 2

Updated: May 7


Continuing the study of material selection for our AUV, we will talk about some more materials that we use and that we think about using in the team, and their main characteristics, advantages and disadvantages.


Fiberglass:


Fiberglass, whose most appropriate name would be Fiberglass Reinforced Polymer, is a material resulting from the superposition of very thin ductile and flexible glass filaments. Polymerization is done by applying some type of resin (in general, polyester), which is responsible for the union of these fibers.


At BrHue, this material was used to make the drawers that hold the electronics inside the main hull. It was chosen because it has a number of advantageous characteristics, such as: lightness, high mechanical resistance and low thermal conductivity, which is very useful because the temperature of certain electronic components usually rises during operation.


Widely used in the nautical industry (in the manufacture of hulls from small to medium-sized vessels and kayaks, for example), fiberglass has become a powerful option for manufacturing the structure of our next AUV. It is worth remembering that factors such as lightness must be considered a lot in the manufacture of a new robot for competition, so that we are not penalized for exceeding the weight limit, and also the high mechanical resistance of this polymer would guarantee us a greater durability of the autonomous vehicle. Furthermore, as it is a recyclable material, we would have a chance to combine technology with sustainable development.


Example of a yacht hull made of fiberglass

Stainless steel:


It is a highly corrosion resistant metal alloy. This is due to the fact that it has chromium in its composition, which makes this material, when in contact with oxygen (responsible for oxidation), create an impermeable protective film, preventing it from being corroded.


In addition to this advantage, through the analysis of its mechanical properties and a structural simulation made in Ansys, we saw that stainless steel would be the ideal material for making the rods that support the electronics drawers inside the main cylinder. Among the different materials analyzed, it was the one that presented the least degree of deformation, when the weight of the electronics was equally distributed in the clips responsible for fixing these drawers.


Structural simulation of the rod made of stainless steel

In the image, we see that the material provides us with a high safety factor, which indicates less possibility of plastic deformation with the weight of the distributed electronics.


A disadvantage of stainless steel, however, is the fact that it is not a very light component. Consequently, it is not something that we consider a lot when we think about making our next structure. However, due to its ease of purchase and good cost benefit ratio, there are high chances that certain components of our next AUV will be made of this material.


Carbon fiber:


It is a material resulting from a long chain of united atoms, which form resistant crystalline chains. A single fiber of this polymer is about 0.005 to 0.01 mm in diameter. However, by joining thousands of wires like this one results in an extremely strong material, managing to overcome the resistance of materials such as steel.

The fact of having a great lightness is what makes the industry, more and more, choose carbon fiber as raw material for the manufacture of its components. It is one of the main composite materials used in the aeronautical industry (because it can efficiently withstand high mechanical efforts and stresses), as well as in the manufacture of Formula 1 vehicle components, which have been able to achieve higher speeds thanks to the innovation of this fiber.


In view of this, carbon fiber, currently, also proves to be a great option for making our next structure.