Week 14

COMPOSITES

ASSIGNMENT

Final Project

  • Read the material safety data sheet (MSDS) and technical data sheet (TDS) for the   resins that you're using.
  • Design and fabricate a 3D mold
  • Produce a fiber composite part in it.

Getting started with this week's assignment, following tasks had to be done :

  1. Designing 3D mold file in Rhino.
  2. Laser-cutting the files and assemble it to make a mold.
  3. Preparing the solution of Resin
  4. Using Burlap and Resin to create a composite.

DESIGNING

I wanted to make a circular anti-clastic surface. I used Rhino for modeling my mold. I followed the following steps:

  1. I started my making a square
  2. Next, lifting 2 opposite end-points to make an anti-clastic surface.
  3. Then I drew a circle
  4. And split the anti-clastic surface along the circle.

Once the basic form was ready, I had to make waffle structure which would act as base for my composite. I used Rhino and Grasshopper for it. I followed the following steps:

  1. First, I used "contour" command to draw sectional lines in X and Y direction.
  2. Next, l used "loft" to form the surface for each cross-section.
  3. Then I used grasshopper to form grooves at intersection for each cross-section.

Files can be found here.

GET FILE

PREPARING THE MOLD

Now that the design files were ready, it was time to prepare the mold. I used the following steps:

  1. Laser-cutting to cut the cross-sections.
  2. Assembling individual cross-sections to form the shape.
  3. Attaching cling-wrap to save the mold for future re-use and easy removal of the composite.

MOLDING PROCESS

For this assignment used Araldrite AW-106 Resin and HV 953 hardener which was available at our Lab. I started by reading the datasheet to understand the behaviour of this resin. It can be downloaded from here.

 

I found the following information very useful for my process of making a composite :

 

  • Araldite AW 106 resin/Hardener HV 953U epoxy adhesive cures at temperatures from 68ºF (20ºC) to 356ºF (180ºC) with no release of volatile constituents
  • Araldite epoxy adhesive components should be stored in their original, sealed containers at room temperature.
  • Handling strength is achieved at 7 hours and cured at 12 hours at 20-25 C
  • The surfaces need to be cleaned before applying the resin.

I used Araldite Epoxy resin and hardener in proportion 1:1 as prescribed. I mixed the 2 solutions thoroughly till it turned homogeneous yellow.

I placed a Burlap sheet on the waffle mold and then applied thin layer of the solution on Burlap. I used a wooden stick to apply the resin and wore safety gloves. I repeated this step thrice to obtain adequate strength.

Next I placed the composite in an Air-tight bag and sucked the Air out using a Vacuum cleaner. This ensured that there are no Air bubbles left.

This puts the composite into compression. I let it dry for next 3-4 hours to gain sufficient strength and stiffness.

It acquired adequate strength in only few hours and became very hard. I removed it from the Bag and used scissors to cut the edge into round shape. This how my composite looked like.