For this week were introduced to composites and the different ways we could achieve the results as well as the respective procedures, materials and tools. This is the process that is found in many industries, a common example of this would be carbon fiber composites and fiberglass.
This week we had to digitally fabricate a mold in a certain shape and use what we learned to cast a composite.
Individual Assignment:
Read the safety data sheet (SDS) and technical datasheet (TDS) of the resin that would be used.
Using digital fabrication, create a mold that would be used to cast the composite.
Composites, also known as Fiber-Reinforced Polymer (FRP) composites, are made from a polymer matrix that is reinforced with an engineered, man-made or natural fiber (like glass, carbon or aramid) or other reinforcing material. It is a great fabrication technique as it is relatively low cost and does not need expensive machines. It has been around for more than 6000 years Wattle and daub is one of the oldest man-made composite materials. Concrete is also considered a composite as it is mainly the binding of different materials with different physical and chemical properties. In this case there are main layers stated below:
The matrix protects the fibers from environmental and external damage and transfers the load between the fibers.
The fibers, in turn, provide strength and stiffness to reinforce the matrix and help it resist cracks and fractures.
Fibers -Provides strength and stiffness (glass, carbon, aramid, basalt, natural fibers). I used Cotton cloth as fiber
MATRIX - Protects and transfers load between fibers (polyester, epoxy, vinyl ester, others). I used Epoxy Resin as Matrix.
These two together makes the FIBER COMPOSITE MATRIX and creates a material with attributes superior to either component alone.
The resin availabe at the lab and that would be used is the VIMEPOX BETON-IMP. It is a two component transparent epoxy agent.
Component A is the transparent solvent based epoxy resin.
Component B is the Transparent solvent based hardener.
Based on the datasheet, the resin should harden and set after 10 hours at 20 degrees celcius.
For more information it is advised to read the datasheet if you will be performing any tasks with this resin, SDS
After reading the safety data sheet, it was explicit about the level of precautions that need to be taken, a safety suit, gloves, glasses and mask need to be worn at all times. Any resin is considered highly toxic on its own and when its ongoing the chemical reaction to solidify. And since we are using fiberglass, its as dangerous as the resin as small fibers could easily penetrate the skin and go into the bloodstream and particles of fibers in the air could be inhaled. So safety first with this assignment.
As for the digital fabrication:
First we had to decide which fabrication type would be used in order to design accordingly. I decided to go with the laser cutter, so needed to design a form of press fit kit that would be suitable for use as a cast.
For the design process, I was using Fusion360. I had two designs in mind, one that is an object on its own which is a frisbee, and the other was the body of a torch and then add electronics as in a fan a yellow/red led and a thin piece of fabric that would immitate a flame on the top end.
Here is a video showcasing the design history of the torch, it was relatively simple, I used the sketch to create circles of the dimensions I wanted and offseted planes to create the smaller ones after copying and moving 3 of each circle size and finally outlining the sides extruding it into a body and copying moving 3 other to complete the shape
And another video to showcase the simple propeller design, I basically drew it in a sketch with a center cirlce and used lines and 3 point arcs to make the blades. I made two since I wanted to try pressing the cast in between to see the difference in casting techniques.
For the settings of the laser cutter check the previous weeks for guidance. Because it depends on material and thickness as well as the kerf.
After the assembly was finished it was time to start casting, the first step was to wrap the pressfit shape with a form of fabric, we used women stockings that were available and it did the job. And started sticking the fiberglass layers around while generously applying the resin mix where the ratio is 3.44:1 A,B.
After setting fiber glass and layering the resin on all sides of the torch, I went on wrapping it with another pair of fabric to hold it tight and give it an exterior texture. And added another layer of resin to its surface.
As for the blade it was a different procedure, I simply cut fiber glass layers and used tissue paper to create the composite so I can compare techniques and experiment. Again by applying resin at each layer.
Then added the second part of the blade to press onto the first one squeezing the composite layer in between. I used zipties to press them together from the sides of the blades.
And finally as per the Datasheet, we leave it curing for atleast 10 hours.
Now for some clarity and humbleness, The final result did not come out as expected. The design of the torch had many sharp edges, using the first wrap was probably not the best idea as it took away its shape and now looks more like the dark tower from lord of the rings. Hopefully adding the electronics to it in the near future would make its design a bit more relevant. As for the blade shaped frisbee, it seemed more like a paperplane-ish frisbee as I needed to add many more layers to achieve minimal frisbee like thickness and rigidity. All the mistakes are taken into consideration for future projects, yet it was still a great hands on learning experience overall.
Since the first try of composite was not as successful as anticipated. I gave it another go, this time using a different design where it would be one sided. The idea was to have a sort of shell that would be attached to a wall and have a light inside going around it indirectly. Since we are quite limited with materials and equipment (vaccum machine, board to mill, milling bits, small fiberglass to bend on small objects). I decided to do the best with the available.
For my base layer (mold), I designed triangles that would fit into each other to form a slope and a sort of geometrical design.
Once the design was made, I proceeded and saved the design as dxf to be able to export it to Cura and laser cut the parts using MDF.
Having all the parts cut out, I had some wood glue in between, clamped them down and waited till the next day for them to be firmly stuck to each other.
Now that the pieces are well together forming a firm mold to cast on, I proceded by adding the first layer that would not stick to the mold and be easily removed.
Followed by another layer of stretchy fabric to take the shape of the mold and be a base layer for the others
15 minutes later, I added another thick layer of cloth to create volume and have a good base for the final layers of fabric to follow.
Again with a buffer zone of 15 minutes between each layer I proceded to add 6 layers of fabric (blue and white) to give it some texture and color. I made sure to stick the layers properly to each other to keep the initial shape of the 'steps' between each triangle.
After setting all the layers, not having a vaccum machine. I went on and inserted the cast and mold into a plastic bag and used a vaccum cleaner to suck the excess air out of the bag while keeping my hand around the hose so air does not go back in, once all air was out I twisted the plastic and held it in place so air does not go back in. I think it did a good job vaccuming as I could see the plastic showing the shape of the design. I will keep this for about 15 hours for it to dry and harden properly.
Vaccum bagging is a clamping method that uses the vaccum pressure to hold the resin coated components used in a composite in place and stuck to each other during the curing process. This also increases the bond between the layers as the resin would sweep through the pores of each layer binding them together and letting excess resin flow over the top layer.
The effectiveness of vaccum bagging allows the laminating of a wide range of materials from traditional wood veneers to synthetic fibers and core materials.
Vaccum bagging offers many advantages over conventional clamping or stapling techniques. Although the conventional techniques have a similar result. Using atmospheric vaccum (pressure) would give a more accurate overall binding of composite materials.
The next day, I unwrapped the plastic bag and this is the final result:
This is the result after 24 hours. It is considered solid and has a nice 'knock' to it. I re vaccumed it and will leave it for one more day as there were still some parts that were not fully dry.
p.s: for instructions regarding safety and resin handling please refer to the intro at the top of this page.
