Week17 : Wildcard week (Composites)

assignment

Design and produce something with a digital fabrication process
(incorporating computer-aided design and manufacturing) not covered
in another assignment, documenting the requirements that your
assignment meets, and including everything necessary to reproduce
it. Possibilities include (but are not limited to) composites, textiles,
biotechnology, robotics, and cooking.

My goal

I am making enclosure for my final project: Protolight by composite.
The mold is going to be designed on CAD and 3D printed. Before applying composite on the actual mold, I am making coupon to check durability of the material and accumulation means.

Download files

The mold data

• Front case

• Back case

Material

Fiber

20 denier sheer tights(left), denim cloth (right).

Resin

• FRP Polyester resin for hand lay-up laminating (only Japanese available)

• Polyester resin curing agent(only Japanese available)

SDS summary

• Has volatility, so wear mask, glasses and gloves.

SDS for FRP

SDS for curing agent

Making coupons

Tested with materials and compilation means.

Number of layers

• 1 layer (denim)

• 2 layers (denim)

• 3 layers (denim / tights)

• 4 layers (tights)

Fiber direction

• Crossover (denim)

• Identical (denim)

Result

2 layers of denim or 4 layers of tights seemed strong enough to make enclosure for lighting fixtures.

As tights are easy to handle during composite operation, I decided to use tights as composite fiber material.

Making mold

Designed mold in Fusion360.

download stl :

• Front case

• Back case

3D print models to use it as molds.

Preparing mold

Put the Saran wrapped mold in the tights.

Applying resin

Pay a tension to curing time (in our case it was 15min), be quick but stir them properly to avoid any curing errors.

Use bigger cup and add smaller mass agent to larger mass agent not vice versa for the same reason.

Soak in resin using hands. Making sure that resin evenly spread and not only covering the surface but penetrate to the deeper layer as well.

Layer construction

1. Mold (3D designed & printed)

2. Saran wrap (for separation)

3. Fiber material (used tights)

4. Resin

5. Saran wrap again (for separation)

6. Plastic bag

Compaction

I first vacuumed to draw suck out remaining air in the plastic bug, then sank them into the water to keep the pressure.

Result

The resin cured successfully. However, the mold stuck inside the composite and could not be removed. Also it was impossible to peal saran wrap from the composite as it was almost unified, so I decided to sand it and see how it would look like.

May be it wasn’t a good idea.

Lessons for next time

• Identical to molding and casting, molds need to be designed in the shape easily removed afterwards. Accumulation direction of 3D printing might affect easiness of slipping out molds.
• Do not pour too much resin as the surface gets wrinkly. Try squeeze out unnecessary resin before compaction.

First time failure (making coupon)

Consideration

In our first trial, there was insufficient curing. We asked the support center for help and did some research on it. Here is possible causes of poor curing.

• When the material start to cure, contained paraffin gathers on the surface to form anaerobic area with in the material and curing process starts.

• Even in the process of curing, if the material exposed to air it stops to cure.

• There could be some ingredients within the fiber we were using that interfere the reaction.

• Simply not stirred enough.

In fact, we haven’t stirred the material and the curing agent enough.

BOM

• FRP Polyester resin for hand lay-up laminating

• polyester resin curing agent

• gloves (Nitrile rubber)

• glasses

• ramber wood (for clamping)

• clamps

• cups (for stirring / heat resistant)

• spoons (for stirring)

• vacuum bag

• plastic wrap

• paper towel （キムタオル）

• scale