Prototyping and testing: series of steps and questions to be answered

To investigate the behavior of the floating module, a series of prototypes will be produced and tested in compression. First step is to identify the properties of the core and work towards its optimization in terms of strength and lightness. Once satisfactory results are reached, the optimized core will be laminated with a layer of FRP and, consequently, the properties of the composite module will be defined, through compression tests.

More specifically, the research will be organized as following:

By this stage the questions that need to be answered are summarized as such:

 Core

          

              PET bottles:

o      Grams of dry ice needed

o      Compressive strength of the carbonated bottled containing the dry ice

o      Packing method (vacuum membrane, band, adhesive?)

o      Should the void space between the bottles be filled?

o      Relation/Connection with the FRP layer

              PET Foam:

o      Is the lowest-density version of this foam material (80kg/m³) suitable?

o      Relationship with the exterior FRP layer (needs protection? Infusion holes in foam?)

o      Relationship with the bottles’ caps- should a sheet layer be placed in between?

Then the second phase contains the core with the surrounding FRP layer:

 Issues to be determined by this stage:

FRP layer

            Resin:

o      Resin to be used (in terms of strength, sustainability-recycling, durability)

o      Total thickness of the material

o      Volume shrinkage? Absorption from

             Fiber reinforcement:

o      Fiber reinforcement to be used  (in terms of strength, sustainability-recycling)

o      Type of fabric

o      Volume percentage of reinforcement

o      Direction of reinforcement

             Gelcoat:

o      Is it necessary?

o      If so, what kind of gelcoating should be applied

Floating Component

o      Compressive and bending strength

o      Total mass. How can the optimum strength-mass ratio be achieved?

o      How is the highest part (more foam) behaving in comparison with the lowest

When the stage of prototyping and testing is over, digital simulations will be required, to further understand the behavior of the platform as a whole:

Both for the physical tests and the digital simulations a list of criteria will be made, for the assessment of the different alternatives.

Issues for investigation

At this stage of the design, a composite floating module is developed based on a series of assumptions that have to be clarified in order to guarantee for its efficiency. The designed composite material (GFRP+PET foam+PET bottles) needs to be tested through the production of 1:1 physical prototypes in terms of strength and stiffness. The performance of the module needs to be evaluated and consequently optimized, according to the results of the tests. Once the consistency of the composite structure is precisely defined and its structural properties and behavior are known, simulations have to be done using computational tools, to understand the performance of the floating platform as a whole. 

Alongside the above mentioned research, it is important to investigate the possibility of switching from non-recyclable GPR polyester to indefinitely recyclable self reinforced PET resin, to form the shell of the floating modules. The ability of this thermoplastic composite material to perform structurally needs to be verified.

Starting with the prototype making, first, 3 study cases will be explored and compared on basis of their performance.  According to the results, the next steps of the experiment will be defined. 

Case 1

Case 2

Case 3

Developing the floating platform to meet the design objectives

The floating platform of the house consists of two parts, the floating elements- responsible for the buoyancy- and the structural frame, that form a stiff base for the development of the house. Its geometrical configuration and the material selection are such to comply with the criteria of lightness, waterproofness, simplicity in detailing, usage of waste materials and sustainability. 

Structural concept of the ReVolt House

To begin with, the floating elements are situated at the lower part of the system, in contact with the water. They are formed into hexagonal modules, in order to be evenly distributed inside the circular outline of the house. In section they are shaped in such a way as to create a catenary dome that reassures their co-operation and their staying in place. This dome configuration of the floating platform causes the peripheral elements to submerge deeper into water, receiving larger water pressure and therefore producing larger support reactions at the points where the loads from the walls are received.  Even more, the dome is the optimal choice in terms of stability, forcing the house to behave as a catamaran in all directions. 

The floating elements, according to their position in the dome, are categorized in 4 different types. In one of the categories, at the periphery of the house, the hexagons adjust their shape to fit with the circular boundary of the construction. 

The draught of the house is minimised by reducing the density of the floating platform, without losing however on strength or ability to withstand water pressure. This is achieved by designing the hexagonal modules along the concept of sandwich panels, where the thin exterior layers and the interior foam work together to produce a strong yet lightweight structure. 

Considering the infill of the floating modules, the idea of replacing a standard foam infill with pressurized air that enables the thin skin of the module to withstand the water pressure, can lead to a stronger, lighter and more sustainable structure. The hexagons are therefore filled with polyethylene terephthalate (PET) bottles for carbonated drinks containing powdered dry ice that turns into carbon dioxide, pressurizing the bottles’ vessels. The PET bottles, due to their shape, are distributed in a hexagonal pattern, and joined together with a compression belt. A thin layer of PET foam is introduced at the upper part and the sides of the modules, to achieve the required shape for each hexagon module.  It must be noted that the choice of PET bottles as a construction element relies to their good strength to density ratio, their low cost, and at to the fact that it reduces the embodied energy of the hexagons, by reusing already produced elements. Moreover, taking into account that, due to the organisation of the plan, the mass of the house is not homogeneously distributed, the bottles provide the flexibility to adjust the weight from the platform and reach equilibrium, by filling the bottles in the problematic areas with sand. 

Floating platform: plan, section, details

Regarding the PET foam, it is a foam material produced from recycled PET bottles, and with higher mechanical strength and better insulating properties from eps or pu foam usually applied in sandwich panels. 

The outer layer of the hexagons consists of a 4mm thick glass fiber reinforced (GFR) polyester surface. This decision is based again on the superior strength to density ratio that glass fiber reinforced polymers (GFRP) show but also to the minimal maintenance costs that they demand and their excellent behavior in water.  In addition, because of their non-corrosive behavior, water pollution is avoided, a case very common with steel pontoons. 

Section of floating module

The structural frame of the platform, out of GFR polyester I-beams, comes on top of the hexagon modules in a triangular grid, and is joined with them to ensure that they work as a unified rigid the structure.