Core 1 sally, yorgos, katya, cesar emtech 2015

Emergent Technologies & Design Core1 Documentation Lobster Shell Vol.2 | 2016 Sally Al-Badry, Yorgos Berdos, Katya Bryskina, Cesar Cheng

CONTENTS 1.0 INTRODUCTION

P.04

2.0 MATERIAL EXPERIMENTATION

P.06

3.0 SYSTEM DEVELOPMENT - SCALABILITY

P.08

4.0 FABRICATION _4.1 FABRICATION 1 _4.2 FABRICATION 2

P.10 P.12

5.0 JOINERY SYSTEM _5.1 JOINT AND CONNECTION EXPERIMENTS

P.14 P.15

6.0 COMPOSITE MATERIAL _6.1 NEW COMPOSITE MATERIAL

P.16 P.17

7.0 MATERIAL DEVELOPMENT _7.1 COMPLEX MATERIAL

P.20 P.21

8.0 ENVIRONMENTAL PERFORMANCE _7.1 VENTURI EFFECT _7.2 CROSS-VENTILATION

P.22 P.22 P.23

9.0 CONCLUSION

P.24

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1.0 INTRODUCTION This work is to be read as a continuation in the development of a material system which was started during a biomimetic workshop developed at the AA in fall 2015. In previous studies (ref Vol 1), the biological model of the lobster shell was investigated and a design strategy inspired by the natural system was outlined. The goal at the time, and the underlying basis for the current work, was to develop a design approach for a material system emphasizing on the agency of material with the aid of digital fabrication technologies which could offer insight into an alternative to conventional construction systems that often times dismiss the latent properties of materials.

In our research, the exoskeleton of the lobster was selected as the object of study for its effective use of material. The lobster shell is a continuous yet differentiated surface that serves multiple functions. In the lobster exoskeleton, different regions of the shell have different degrees of stiffness responding to specific mechanical and functional requirements. Perhaps, the most striking observation is the fact that all the parts of the shell despite their difference in function are all made from the same material; a fiber polymer called

chitin which is organized across multiple scales to produce variation in form and differentiation in performance.

By the end of our previous study, several material experiments had been conducted in order to understand the relationship between material and geometry. The work was developed schematically at a small scale using rubber-latex and polypropylene sheets. A series of 2D patterns were developed to act in combination with prestretched latex sheets and generate 3D form as a result of material arrangement responding to the elastic force of latex when stretched.

The material system developed, successfully produced variable states of stiffness and flexibility based on the organization of material and the set of relations established in the logic of the system. The design approach developed suggests the possibility of a system with possible architectural applications. Our present work in this volume mainly concentrates on questions of scalability and fabrication of the material system previously developed.

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INITIAL MATERIAL EXPLORATION 2.0 MATERIAL EXPERIMENTATION 1. LIQUID LATEX + PLASTIC MESH LIQUID LATEX + PIANO WIRE

6

2. LIQUID LATEX + PIANO WIRES LIQUID LATEX + PLASTIC MESH

3. LATEX SHEET+ PIANO WIRES LATEX SHEET + PIANO WIRES

4. LATEX SHEET+ POLYPROPYLENE LATEX SHEET + POLYPROPYLENE

LYCRA + P

+ POLYPROPYLENE

5. LYCRA LYCRA + + POLYPROPYLENE POLYPROPYLENE

1. In the first experiment, liquid latex and a plastic mesh membrane were employed to create a sheet of material with the mesh fibers embedded in the latex. By shifting the individual fibers into an undulating pattern arrangement the result we achieve is a reinforced latex membrane which reacts to tensile forces when post-streched creating 3D peaks and valleys across the surface of the material.

2. The next experiment was carried out using liquid latex and piano wires. A weaved pattern in which the space between the piano wires increases across the material is layed out. The combination between these two materials produces a reinforced sheet of latex that performs differently according to the changing spacing between the wires , however, it does not maintain its deformed shape without the use of anchor points at its boundary edges.

3. For this experiment a sheet of latex was pre-streched in two directions and a piano wire weaved pattern was applied onto it. When the bidirectional stress is released the sample deforms and finds its final form. The final global geometry results in a doubly curved surface in a defined stable state.

4. For these experiments a pre-stretched latex sheets in combination with a lasercut polyproperlene 2D pattern were used.

After the pattern is applied, the composite sheet deforms and holds its final form in a stable state. Thickness of material as well as geometrical configuration play a crucial role in the form-defining process.

In the case of polyproperlene, a sheet material that is available in various thicknesses and can be cut to custom dimensions, the parameters that guide form definition can be better controlled.

5. One of the first tests for scaling up was made with pre-stretched lycra and thicker polypropylene (1.8 mm). The thickness of the fibers was increased and in this test the fibers were arranged parallel to each other. Lycra was pre-stretched and connected to the frame with metal screws. This produced enough force to deform the frame due to the parallel fiber arrangement, however, the screws represented additional weight making its own weight to high to be self supportive. To achieve a self-supportive state, post stretching was required leading us to think of other alternatives to improve the structural integrity of the system.

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3.0 SYSTEM DEVELOPMENT- SCALABILITY

SYSTEM DEVELOPMENT

LATEX RUBBER SILICON

RUBBER FABRICS Joints

PINNED ADHESIVES

GROMMET CABLE TIES

SUPER GLUE

SEWING

SPRAY GLUE CONTACT GLUE

8

SHEETS

RODS

3D PRINTING

POLYPROPYLENE

PVC

PVA / ABS

LYCRA NEOPRENE

PANEL REINFORCEMENT

“But yet it is easy to show that a hare could not be as large as a hippopotamus, or a whale as small as a herring. For every type of animal there is a most convenient size, and a large change in size inevitably carries with it a change of form.”

(On being the right size.-Haldane.)

HINGE CONTROL

The diagram on the left shows the basic elements that make up the system and the possible material options that were investigated for transitioning to a new scale. The system requires an active base membrane and a reactive fiber element.

An important condition for the base membrane is to be able to store enough elastic energy at this scale to create the necesMEMBRANE sary action force on the fiber elements to induce deformation and generate 3D form. For the membrane two categories of material were tested; stretchable fabrics and various types of rubbers. For the fabrication of the 2D fiber patterns two paths were explored additive and subtractive manufacturing.

2

PANEL REINFORCEMENT

1 HINGE CONTROL

1

MEMBRANE

PANEL REINFORCEMENT

1. MODEL WITH NO STRAPS HINGE CONTROL

Sheet material as opposed to other material options such as rods or tubes, allowed us to have better control over the STRAPS cross-section of the fiber elements. A first prototype was developed with CNC polypropylene sheets for the fiber elements and lycra for the base membrane. Even though lycra is a stretchable material, at this scale it did not perform adequately and stored enough force to have any effect on the fiber patFLAT FIBERS tern as shown in Fig 1. [top right] To make up for the necessary force and the poor performance of the lycra, we developed a strapping system to reinforce the pattern and create tension in the areas needed. This addition to the system made the prototype a lot stiffer and able to support its own weight.

2

2

2. MODEL WITH REINFORCEMENT 1. MODEL WITH NO STRAPS

2. MODEL WITH REINFORCE

1

STRAPS MEMBRANE

HINGE/ FLEXIBLE 1. MODEL WITH NO STRAPS

HINGE/ FLEXIBLE 2. MODEL WITH REINFORCEMENT

STIFFNESS

STIFFNESS

FLAT FIBERS STRAPS

HINGE/ FLEXIBLE STIFFNESS FLAT FIBERS

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3D PRINTED FIBERS 4.1 FABRICATION: ADDITIVE MANUFACTURING

CHANGING THICKNESS

mm

CHANGING THICKNESS 3mm

HICKER SECTION

THICKER SECTION

STIFFNESSSTIFFNESS

10

1 mm 1 mm

THINNER SECTION

THINNER SECTION

FLEXIBILITY FLEXIBILITY

4.1 ADDITIVE MANUFACTORING Rapid prototyping is a fairly new fabrication technology, with the first available machines coming on the market in the late eighties and early nineties. A lot of research and development has been done in the last two decades, trying to improve the material properties of rapid prototyping technology. This research aims to get the additive fabrication processes one step further towards the implementation of these techniques on various architectural project in different scales and not just to models and prototypes.

During our quest for the most suitable fabrication process that would allow our system to scale up and remain structurally efficient, we explored the possibility of 3D printing the pattern of our panels. This technique would give us two main advantages. The first one is that we could enter one level deeper into the fibrous arrangement of the pattern and start elaborating the geometry inside each fiber itself. This would give us a system closer to the natural way with which the lobster controls the varying stiffness along its shell (Vol1).

Another important advantage was that with 3D printing we would be able to differentiate the thickness of our pattern

locally and regionally, without wasting any material. The differentiating thickness of the fibers, combined with their changing geometry would give a greater control over the variation of the global structure’s stiffness.

We experimented with this technique, initially using a 3D doodler pen and ABS plastic but we were not able to fully control the path that the pen followed and ABS plastic was too brittle. Then we tried 3D printing using an Ultimaker2 printer filled with natural PVA rubber, a very flexible water soluble material. This set of experiments gave us some successful results; the PVA pattern was deformed as expected when glued to the prestreched latex sheet. But this technique was not scalable enough because we were limited by the dimensions of the Ultimaker’s bed (150mm*150mm).

An option for further development using this technique would be researching in robotic end-effectors that could efficiently deposit natural PVA on latex sheets and form our fibrous pattern.

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4.2 FABRICATION: SUSTRACTIVE MANUFACTURING

FABRICATION 2 : SUBTRACTIVE MANUFACTURING USING CNC MILLING

Scalability

Variable Thicknesses laser cutter bed

CNC mill bed

All the panels are made of flat sheet materials

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USING CNC MILLING 4.2 THE OPTION OF CNC MILLING

ill be

The other fabrication option that we explored, which was the one that we finally used for fabricating the larger model, was the subtractive manufacturing and more specifically CNC milling. During the biomimetics material system exploration (Vol1) we used laser cutting to fabricate our panels out of polypropylene sheets. This technique was not directly scalable since we were limited by the laser cutter bed dimensions as well as from the inability of laser-cutter to cut thicker polypropylene sheets (more than 1.5mm) .

each panel and that could further contribute to the control of the structure’s stiffness both in regional and global level.

Using the CNC mill, we were still able to produce our prototype out of flat sheet materials; a stretchable membrane and the polypropylene pattern, which became much thicker (3mm). Furthermore, we could change the thickness of the polypropylene fibers in different areas of

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5.0 JOINERY SYSTEM

MEMBRANE - JOINERY SYSTEM -

CONTACT GLUE

SPRAY GLUE

EPOXY ADHESIVE

SPRAY ADHESIVE

CONTACT ADHESIVE

CABLE TIES

LATEX RUBBER

FABRICS

SPRAY ADHESIVE

CABLE TIES

14

EPOXY ADHESIVE

GROMMETS

GROMMETS

BOLTS

SEWING

EPOXY ADHESIVE

CABLE TIES

CABLE TIES

FABRICS

SPRAY ADHESIVE

SPRAY GLUE

5.1 JOINTS AND CONNECTIONS

LATEX RUBBER

Part of the experiments involved testing options for joining the polypropylene fiber pattern with the elastic membrane. Finding a suitable connection for the fibers and the membrane was essential in the process system. The SPRAY of rescaling the material CONTACT ADHESIVE ADHESIVE success of the system relies entirely on the connection of these two elements. It is possible to find a material for the fibers which works well at a larger scale and also a base membrane that has the force to act on the material at this scale, however if they cannot be connected with each other by means of an efficient joint, the entire system would fail.

A number of experiments were conducted testing two types of membranes; rubber-latex (in various thickness) and stretchable fabrics (lycra and scubba). Since latex is a material with low shear strength, it is impossible to join it to the fiber material with any pin connection without breaking it. For this reason, different types of glue adhesives were tested to try to establish the best connection possible. The advantage of gluing is that the entire surface area of the fibers is bonded to the membrane. The result is a stronger deformation of the composite material as illustrated in the diagram on the right. On the other hand, fabrics failed to bond with most of the glue adhesives tested in the experiments but performed well with the different pinned connections tried (cable ties, bolts, grommets), with the only disadvantage that the deformation was not as desired.

GROMMETS

LATEX RUBBER

CONTACT GLUE

GROMMETS

BOLTS

SEWING

EPOXY ADHESIVE

Figure 1

Figure 2

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6.0 COMPOSITE MATERIAL

COMPOSITE MATERIAL - LATEX-COATED LYCRA LYCRA IS COATED WITH LIQUID LATEX IN ORDER TO CREATE A STRONGER MEMBRANE IN CONTROLLABLE THICKNESSES. COMPOSITE MATERIAL - LATEX-COATED LYCRA THE NEW COMPOSITE MATERIAL RESISTS HIGHER TENSILE FORCES. LYCRA IS COATED WITH LIQUID LATEX IN ORDER TO CREATE A STRONGER MEMBRANE IN CONTROLLABLE THICKNESSES. THE NEW COMPOSITE MATERIAL RESISTS HIGHER TENSILE FORCES.

1 mm FABRIC (LYCRA) FABRIC (LYCRA) LYCRA + 1 LAYER OF LATEX LYCRA + 1 LAYER OF LATEX

1 mm 1 mm 1 mm 1.2 mm

LYCRA + 2 LAYER OF LATEX 1.2 mm LYCRA + 2 LAYER OF LATEX

1.5 mm

LYCRA + 3 LAYER OF LATEX 1.5 mm LYCRA + 3 LAYER OF LATEX

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6.1 NEW COMPOSITE MATERIAL After choosing CNC milling as a fabrication technique for producing our polypropylene panels, we started investigating what sort of flexible membrane we could use to achieve enough deformation and double curvature in a similar way as in the biomimetics project (Vol1).

Latex rubber membranes were providing enough tension when pre-stretched for deforming the 2D panels, but since we scaled up it was not possible to glue the latex sheets efficiently to the polypropylene panels with any kind of adhesives, as shown in the joinery experiments. So we conducted further experiments where we tried to connect the latex sheets to the polypropylene pattern by piercing it (using grommets and cable ties). The result was that the holes produced were acting as weak points of the membrane and the latex tended to tear apart when stretched, most of the times before even connected to the panel. We got similar results when testing gluing or piercing and then stretching other kind of rubber membrane sheets, such as silicon sheets and untreated rubber sheets.

Moreover, we conducted tests using lycra as the flexible membrane that would be

prestreched and then deform the polypropylene panel. The main advantage of lycra was that it could be pierced and stretched without tearing apart. But the main disadvantage was that made us look for an alternative was that lycra did not provide enough retraction force to deform significantly the structure after released. In addition to that, lycra deforms plastically if prestreched beyond a certain point and does not return to its initial state.

These experiments lead us to create a new composite material, which is a combination of lycra with liquid latex, which harnessed the advantages of both materials. It is pierciable and provides enough retraction force when prestreched. This material was produced by coating the lycra sheets with three layers of natural liquid latex, as shown on the opposite page.

In the following pages a material performace analysis of the new composite material is presented. The properties of the material are evaluated in comparison to base material that make up the composite.

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MATERIAL PERFORMANCE LYCRA

LATEX

x = 150% y = 200%

ELASTIC ( x < 150%, y < 200% ) EASY TO ASSEMBLE POSSIBLE TO GLUE TO POLYPROPYLENE

18

LATEX-COATED LYCRA

x = 250% y = 250%

ELASTIC ( x = y, x < 250% ) IT STRETCHES BOTH DIRECTIONS EQUALLY WATERPROOF HIGH CONTRACTION FORCE DIFFICULT TO GLUE TO POLYPROPYLENE TIME CONSUMING ASSEMBLY PROCESS

x = 150% y = 200%

ELASTIC EASY TO ASSEMBLE HIGH CONTRACTION FORCE PIERCEABLE IT DOES NOT GLUE TO POLYPROPYLENE LESS ELASTIC THAN LYCRA AND LATEX

MATERIAL ANALYSIS LATEX COATED LYCRA (Y) (Longer Streching)

LYCRA (Y) (Longer Streching)

BEFORE

f1 f2 1

2

3

4

5

4 X STRONGER THAN LYCRA

AFTER

1

2

3

4

5

Length Strip: 160 mm Displacement: 50 mm Weight: 1 Kg F1: 9.8 N

Length Strip: 160 mm Displacement: 150 mm Weight: 1 Kg Force: 9.8 N

Length Strip: 160 mm Displacement: 150 mm Weight: 5 Kg F2: 49 N

Lycra was deforemed 20mm.

LYCRA (X) (Shorter Streching)

3

3

3

LATEX COATED LYCRA (X) (Shorter Streching) LATEX (Equal Streching) 4

4

5

5

f1 f1

f2

Length Strip: 160 mm Displacement: 115 mm Weight: 1 Kg Force: 9.8 N

Length Strip: 160 mm Displacement: 15 mm Weight: 1 Kg Force: 9.8 N

Length Strip: 160 mm Displacement: 150 mm Weight: 5.8 Kg F2: 56.8 N

Length Strip: 160 mm Displacement: 125 mm Weight: 1 Kg Force: 9.8 N

f2

Length Strip: 160 mm Displacement: 150 mm Weight: 1.3 Kg F2: 12.7 N

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2.0 MATERIAL DEVELOPMENT - COMPLEX MEMBRANE

7.0 MATERIAL DEVELOPMENT

22

20

7.1 COMPLEX MATERIAL 2.0 COMPOSITE TheNEW next step in our material experimen- could be harnessed to optimize the use tations was the further elaboration of the of latex reinforced areas among the lycra MATERIAL

new composite material that we invented fabric. In the specific experiments, we before (the latex coated lycra). We con- achieved more tension force in the middlewe part of the gradually tinued aiming to generateThen, coated thefabric, wholewhich thing with liq- deThe next experimenting step in our material experimengrades towards the edges. a membrane that provides the necessary tations was the further elaboration of the uid latex, as shown on the opposite page. tension to ourmaterial structure efficiently.After an hour, we released the fabric from new composite thatmore we invented Thus, (the to control the areas where the re-the MDF mold by simply pushing the patbefore latex coated lycra).

We conaction force of the fabric was bigger, tinue experimenting aiming to generate wetern pieces. a mechanism allowed a constructed membrane that provides the that necessary tension to our structure us to coat with liquid more latex efficiently. only specificThe resulting new material resembles a Thus, the areas where the re- controlled anisotropic behavior, which areastoofcontrol the lycra. action force of the fabric was bigger, we could be harnessed to optimize the use constructed mechanism allowed To achieve athat, we laser that cutted an MDFof latex reinforced areas among the lycra usboard to coat with liquid latex only specific containing the pattern of the desir-fabric. In the specific experiments, we areas the lycra.areas of our new compos-achieved more tension force in the midable of latex-free ite material. Following this, we covereddle part of the fabric, which gradually deTothe achieve that,MDF we laser cutted MDF negative piece withanthe lycragrades towards the edges. containing the pattern of the desirable and we repositioned the pieces on their latex-free areas of our new composite belonging holes protecting the lycra from material. Following this, we covered the being covered with latex. negative MDF piece with the lycra and we repositioned the pieces on their belongThen, wetraping coatedthe thelycra. whole thing with liqing holes, uid latex, as shown on the opposite page.

After an hour, we released the fabric from the MDF mold by simply pushing the pattern pieces away.

The resulting new material resembles a controlled anisotropic behavior, which 23

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8.0 ENVIRONMENTAL SYSTEM

VENTURI EFFECT y x

5.1 VENTURI EFFECT

yâ&#x20AC;&#x2122; xâ&#x20AC;&#x2122; y x

The material system is waterproof because of Latex Coated Lycra and has an interesting translucent effect because of the layering polypropylene and fabrics. Also, with the developing of this material system was discovered that a variety of global geometries with different panel system design and organization can be generated that can be optimized to response to climate conditions.

One of the variations of a global geometry is creating a different radius condition that provides a venturi effect and accelerates wind in the inner section. In this case the panel organization reduces the amount expansion and constriction of fibers towards the center that creates a smaller section, but it is still creates a continuous pattern.

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BUOYANCY

5.2 CROSS-VENTILATION

y1 x1

the variables that control the relation of the hight (y) and span (x) are:

y’1

-the polypropylene thickness -the strechable membrane -the amount of prestreching -the pattern on the polypropelyne

Another possibility of global geometry that became interesting for the investigation has an opposite effect to the venturi effect. Panel organization and fiber arrangement creates a bigger radius in the middle and smaller in the ends. That with the opening at the different levels creates a buoyancy effect.

x’1

y1 x1

ELASTIC ( x < 150%, y < 200% ) EASY TO ASSEMBLE POSSIBLE TO GLUE TO POLYPROPYLENE

DIFFICULT TO GLUE TO POLYPROPYLENE TIME CONSUMING ASSEMBLY PROCESS

During the development of the material system strategy, certain areas are not connected with the geometry, which could be used as a naturally created system of openings. In this case, openings were placed at the lower level on one side and on the top at the other side to create the movement of the air DIFFICULT TO GLUE TO POLYPROPYLENE DOESto NOT GLUE TO POLYPROPYLENE into and out of the structureITdue differential pressure. Also, TIME CONSUMING ASSEMBLY PROCESS LESS ELASTIC THAN LYCRA AND LATEX the openings have a variety of combinations and can be controlled parametrically by the size and the gap of the openings with geometry that lets us create different shading effects. This opening system can be applied to variety of geometries.

IT DOES NOT GLUE TO POLYPROPYLENE LESS ELASTIC THAN LYCRA AND LATEX

ELASTIC ( x < 150%, y < 200% ) EASY TO ASSEMBLE POSSIBLE TO GLUE TO POLYPROPYLENE

VENTILATION

ELASTIC ( x < 150%, y < 200% ) EASY TO ASSEMBLE

Exhaust air out at high level

POSSIBLE TO GLUE TO POLYPROPYLENE

VENTILATION

DIFFICULT TO GLUE TO POLYPROPYLENE TIME CONSUMING ASSEMBLY PROCESS

IT DOES NOT GLUE TO POLYPROPYLENE LESS ELASTIC THAN LYCRA AND LATEX

VENTILATION Exhaust air out at high level

Exhaust air out at high level

Fresh air in at low level

Outlet

Inlet Fresh air in at low level Controlling shading and ventilation with geometry.

Outlet

23 Inlet

24

CONCLUSION In this work the main aim is to develop the proposed material system and provide solutions for scalability and fabrication.

We were interested in scaling the proposed system to up to human-scale and increase its load-bearing capacity. Different alternatives of materials are proposed to be used as the membrane and the fibers. After investigating different kinds of membranes, we proposed a composite material to create a stronger membrane in controllable thicknesses that could resist higher tensile forces. This composite material is used in combination with thick polypropylene fibers. The fiber arrangement is designed to meet different functional requirements and achieve geometries that exhibit double curvature at local and global scales.

experiments proved that gluing polypropylene with membrane is not possible so we replaced it with cable ties. After all, many fabrication issues have been sucessfully solved by using the proposed composite material as a membrane.

The material system approached demonstrates the possibility of creating a three dimensional doubly curved geometry out of flat two dimensional sheets by taking the advantaged of the materials properties.

On the other hand, the fabrication was another essential aspect to look at. In order to fabricate the proposed system two fabrication options were explored for the generation of fibers; additive manufacturing technique such as 3D printing which is available now with the use of robotic arms and subtractive manufacturing using the CNC milling.

Furthermore, sets of experiments have been conducted to solve the joinery system and to choose the right material; the

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