Design-driven integrated development of technical and perceptual qualities in foam-formed cellulose fibre materials

Abstract

Design-driven process entailing iterative prototyping was used to develop foam-formed monomaterial structure made of renewable and recyclable biomaterials suitable e.g. for sound insulation in interior spaces. Interactions between wood-pulp fibres, the perforated mould and the forming process opened opportunities for multi-scale material design, which re-defined the direction of the research. This finding entailed the simultaneous formation of macroscopic 3D forms, surface textures, and micro-porous material structures. These multi-scale properties affected the material’s technical and perceptual qualities. The dyed pulp together with the multi-scale forms provided interesting variations in visual quality. Moreover, the surface texture enhanced the material’s tactile properties and gave a higher quality feel and enhanced rigidity.

Appendix: Design-driven process

The research was executed through a design-driven iterative process. The cyclic iterations adjusted the direction of the research through the various development phases as new knowledge was brought to light. The process was flexible in nature, and thus the course and even goals of the research could be clarified and changed as the work progressed. The point was not to establish a fixed hypothesis or point of view from the outset. Rather, learning took place through doing, and the process and prototypes themselves opened up new interesting research trajectories.

The iterative design-driven process included the following phases (Fig. 12):

Fig. 12

This diagram represents the stages and sequences of the design-driven iterative process used in the research. The numbers represent the key phases of the process, such as the designing and testing of prototypes. The loops highlight the iterative nature of the process. For example, the production of a prototype brings forth new information that urges the process a few steps back, for re-adjusting the approach based on the newly acquired information. The various phases are explained in the text below

• 1. Defining an acoustic interior element as the driving application for the research The first task was to find an example application to guide the prototyping. An acoustic interior building panel was considered ideal in terms of the material, the foam forming process and the design-driven approach.

• 2. Designing a rectangular shaped panel with smooth contours Moulding of smooth forms was chosen, as this was expected to be less challenging than forms with sharp angular features. The panel design incorporated two round elevations of different heights to test the moulding of different radii.

• 3. Prototyping the rectangular panel with a plywood mould and white pulp Drying was enhanced by removing water through the holes in the female part by vacuum and by applying additional pressure with the male part, which resulted in quite a dense fibre-network structure. The two elevations on the panel did not form equally well: the higher formed much better than the lower. The plywood mould also broke midway through the testing. The prototyping thus had limited success.

• 4. Designing a triangular shaped panel with smooth contours The design was changed to have steeper forms with tighter radii for inspecting moulding limits. All four “ridges” of the form were equally high, in order to avoid moulding problems with forms of varying heights. Again, the mould consisted of two parts, but this time it was first made out of gypsum to avoid disintegration due to moisture.

• 5. Prototyping the triangular panel with a gypsum mould and dyed pulp The moulding of the material succeeded better than with the first mould. However, the gypsum mould absorbed moisture. This significantly slowed the drying of the formed material, which was kept between the male and female moulds to minimize material shrinkage.

• 6. Prototyping the triangular panel with a polystyrene mould and dyed pulp A densely perforated polystyrene mould was produced to speed drying of the prototype and make the mould lighter and moisture durable. The dense perforation of the mould with its sub-millimetre sized holes was copied during the moulding onto the prototype forming a regular surface texture. At this point the potential of a multi-scale moulding approach was realized.

• 7. Designing the V-pleat shaped panel with angular contours The design was created to study moulding of sharper and more angular forms. The male part of the mould was omitted, and thus forming took place solely by drainage through the female mould. This resulted in thicker prototypes.

• 8. Prototyping the V-pleat panel with a rib-weave wire-gauze mould and dyed pulp The mould was made from rib-weave wire gauze to examine its effect on the prototype’s surface texture. The mould created a densely perforated structure that enabled quick water removal, good moisture durability and a dense texture on the material surface.

• 9. Prototyping the V-pleat panel with a 3D-printed PLA mould and dyed pulp The 3D-printed mould was tested to see whether the use of a low-resolution print would allow water leakage through the small gaps between the print paths. The mould worked well and there were no problems with drainage. There was no noticeable surface texture in the final material structure.

• 10. Designing planar moulds used for surface texture experiments Eleven different planar moulds were prepared containing perforations of varying size, density and shape. The holes were located on a square lattice. The relative penetration area varied between 13 and 44% depending on the geometry. The smallest area (16%) was obtained by three different geometries as shown in Table 2, which allowed estimation of the importance of geometry details in texture formation.

• 11. Prototyping surface textures using laser cut and 3D printed planar moulds and white pulp The planar sheets worked well for studying the moulding of the surface textures.