I was wondering about the status of more environmentally friendly alternatives to epoxy + carbon/glass/kevlar fiber composites. I came across articles that studied the use of PLA in combination with various natural fibers (jute, hemp etc.) with relatively good results related to improvement of mechanical properties and fiber adhesion.
Since there is currently nothing else better to do (country under lock-down) I decided to document an attempt at making the bio-degradable composite and using it to build a drone frame.
As most of the drone parts finally arrived from China, I decided to assemble the components to the frame that I build. Since I do not have any special use case for the drone (besides a test platform for the composite material) I choose common and affordable components:
With the help of many YouTube tutorials I managed to wire and configure the drone with Cleanflight configurator that was supported by my Naze flight controller. I will not go into the details of the assembly and configuration process since I do not think I can add any useful information that is not already available.
With the help on many cable-ties :), the final results looked like this:
I mentioned before that not all of the components arrived. Propellers were still missing so I asked my brother to 3D print me some propellers just to test if everything works as expected. We managed to get the drone of the ground for a few seconds before crashing and braking the propellers.
I will post a video of this strange contraption in flight when the propellers find their way to my postbox :)...
While cutting PLA/jute composite sheets for the drone frame I decided to perform a simple test of material strength just to have a rough comparison with standard 3D printed parts.
I have cut small PLA/jute blocks and printed the same shape on the 3D printer.
I drilled the holes into the blocks and secured them on the table. Pieces were then gradually loaded with a digital fish scale to record the maximum force at the time of failure. I know there are standardized tests for such measurements, but for the first test this method should suffice.
From the results we can not see a significant improvement in case of the PLA/jute composite, but hey at least it did not turn out much worst :).
Based on the failed parts we can see that both the fill factor of the jute and the adhesion between both components could be improved. This is something to think about for the next batch of sheets if it comes to that.
Now there is nothing else left to do than to build the drone frame while waiting for other components to arrive from China.
For my first attempt at making the material for the drone frame I decided to go with a transparent color of PLA material. This will enable me to better judge the success of fiber adhesion and create a material with a natural look.
I chose a relatively fine cloth with jute fibers as the laminat for the composite.
I prepared a small baking tray with the following components from bottom to top:
-cut pieces of PLA (1/3 of composite volume)
-2 sheets of jute cloth
-cut pieces of 1/3 (1/3 of composite volume)
I placed the tray into an old pizza oven I had laying around for 30min at 220 °C in a well ventilated workshop. While checking the progress of PLA melting I pressed repeatedly on the sheets with a flat jig to evenly distribute and flatten the melted PLA.
I am quite pleased with my first attempt, as it seems that some of the panels I made will be usable for the drone frame. PLA mostly managed to get through the jute cloth, but some of the fibers seem more saturated with PLA than others.
Sheets are ready to be cut into drone frame pieces (sending them to my brother, so he could also have some fun during lock-down :)). I hope there will be samples left to perform some testing, comparing the temperature and mechanical properties to plain 3D printed PLA.