1. An introduction to composites design and manufacturing

2. Potential Instructors
Bo Pollett
Fred Briggs

3. Class list
11/23/13 – 13:00
Corry Lazarowitz
David Stewart

4. Overview Introduction to Composites Manufacturing Techniques
Part Selection
Simple parts
Complex parts
Vacuum Mold Making
Vacuum Thermoplastic Forming
EEOP
Tool Prep
Wet Layup
Trimming

5. Introduction
A composite part is defined as something that is made with more than one material
The most commonly engineered composites are filament reinforced plastics like carbon fiber and epoxy

6. Materials Overview - Fibers
Different fibers provide different physical properties as well as a different look. Here are some general material categories:
Fiberglass is a great all around material with medium strength, a low cost and lower weight than wood, plastic, or metal
Carbon fiber ranges from still to really stiff and is well suited for aircraft and performance applications where weight reduction is worth the high cost
Kevlar is in between fiberglass and carbon in terms of stiffness, cost, and weight, but has a very high impact energy resistance and is well suited for impact resistant applications like boat sails and sports equipment

7. Materials Overview - Matrix
The glue that holds the fibers together is called a matrix. It is usually a long chain hydrocarbon based plastic, but there are lots of specialty matrix materials as well. Here are a few examples of common matrix materials:
Polyester or Vinylester resin is a 1 part liquid that required a few drops of MEKP catalyst to begin hardening. It is low cost and low strength material. Good for everyday applications like civil engineering or commercial products like surfboards.
Epoxy is a 2 part resin that has very specific mixing ratios based on the manufacturer. This resin is stronger than the esters but also more expensive.
Ceramic matrix is a powder that is kiln fired like clay to create a brittle but very high temp composite. This is often found in rocket motor parts or brake pads.

8. Manufacturing With a Mold Tool
Painting resin on fabric is called “wetting out”
Placing carbon fabric on a tool and painting it with resin will cause the carbon to harden in the shape of the tool
Mold Tool
Wet Layup
Cured Part

9. Mold Tool Basics
Mold tools for a new part are often made with a cnc machine
If a part already exists, a mold tool can be made for less cost by using the original part as a “master” or “plug”
The mold tool will be an inverse of the part, called a “splash”
It is important to factor in material thickness when deciding which side of a part to use for the splash
A splash can be made using various methods and materials
Vacuum thermoplastic forming
Composite wet layup
Resin casting
Latex painting
Different tool making methods have unique strengths and weaknesses

10. Simple Parts Select a part to use as a “master” or “plug”
The part should have a smooth surface
The part cannot be “trapped”
The part must have holes sealed up with tape or clay
The part should have a continuous edge that can be extended
The part should be 1-sided or multi- sections

11. Complex Parts Closed structures require special layup methods
Closed or trapped structures require special tooling
Complex and accurate cutouts must be made with a cnc router or a waterjet cutter
Core or other inter-laminate inserts

12. Vacuum Thermoplastic Forming
Vacuum forming can be used to create composite molds
Place the plug (original part) on the vacuum table
Hold the plug in place with tape, clay, or pins
Create an extended edge of part (EEOP) if the plug has hard edges (see next slide)
Heat plastic sheet
Place hot plastic sheet over part and apply vacuum
When plastic is cool, remove it from the vacuum table
Locating pins and edge of part scribes can be added to the plug in order to improve the accuracy of the final product

13. Extended Edge of Part (EEOP)
An EEOP will allow the tool layup to go beyond the edge of the part creating a continuous edge
The composite part will be trimmed afterward and maintain the exact same shape as the original part

14. Tool Prep
The resin will soak into the fabric and cure in any shape, which is why an accurate mold tool is important
Resin will stick to almost anything when it cures, so a release agent like wax must be applied to the mold tool before putting resin on it
The plastic sheet tool may be flimsy and require reinforcement of some kind

15. Wet Layup
Begin by preparing all the material you will need for the whole layup process, a checklist can help
Covered work table, gloves, mixing stick, resin, mold tool, paintbrush, cut fabric, cleaning supplies
Mix the resin as specified by the directions, the ratio has to be very accurate and mixing has to be very thorough
Paint a layer of resin on the tool
Lay the first ply of fabric on the tool being sure to press it into all the corners
Gently brush a layer of resin on top of the fabric, be sure not to pull the fabric or it will come off the surface of the tool
Add the next layer of fabric and repeat until every ply has been used
The amount of fabric and thickness of resin coats will determine the strength and weight of the part
Set the part aside so it can cure undisturbed at F

16. Trimming The part will come out of the mold with long, rough edges
The part will have to be trimmed back to the original edge of part line
This can be done with scissors or may require a rotary tool depending on the thickness and material
The final edges should be sanded to remove any splinters
Be careful when cutting or sanding composites, the material has very sharp edges and makes toxic dust, always wear proper breathing and eye protection when trimming

17. Safety Precautions
Wear a mask when working with resin and work in a well ventilated area. Working outdoors on a warm day is the best option. Be sure not to work in an area where others may be effected by the fumes of the resin.
Resin can “cook off” if it is left in the cup too long. This is due to the fact that a higher volume causes more reactions and a more exponential runaway of the chemical reaction. This reaction can reach 300F and cause burns or damage. If this occurs, put the cup into a well ventilated area immediately away from other people or objects.
Fibers can cause rash or skin discomfort. Wear gloves when handling large amounts of material. Do not get material in contact with face, eyes or soft tissue.
Wear a mask when sanding or trimming composites. Composite dust is especially dangerous since it is so fine. Sanding or trimming can cause dust to get into the air, lungs, and eyes. Be sure to sand in a well ventilated area away from other people. Carbon dust is also conductive and will cause electronics to short out. Kevlar materials are especially tough and can overheat and destroy power drilling and cutting tools. Be sure to have proper cutting bits and blades for composites. When drilling composites, be sure to clamp down parts so that they cannot get caught in a drill and begin spinning.

18. Process Overview
Gather prep materials: scissors, painters tape, release agent
Prepare mold surface: mold tool sealed or a permanent plug sanded
Optional vacuum bagging materials: plastic film, peel ply (breather), bleeder cloth, sealant tape, suction ports (frogs), vacuum line, vacuum gauge, vacuum pump
Cut fiber to size: woven sheet, filament tow, braided sock, etc.
Gather mixing materials: Mixing materials: cups, stir sticks, gloves, mask, cleaning agents, brushes
Mix matrix: polyester resin, vinylester resin, epoxy, etc.
Apply fibers and resin to mold surface, ensure complete wet out
Allow matrix to cure per manufacturers instructions
Apply vacuum bag for lower weight final product
Remove part from mold using rubber or plastic shims
Trim part with proper rotary tools, be sure to use a mask and proper ventilation

19. Resources

20. Questions

21. Project 1 – Light Switch Plates
Thermoform a light switch plate
Be sure to cover the holes with tape or clay
Leave witness marks to make trimming easier
Use the thermoform as a tool for layup
Use one ply of carbon and one ply of glass
Vacuum bag all the plate covers in one envelope bag
Use the Blacktoe CNC router to trim the holes
A jig may be used to locate the hole centers and make the process go faster

22. Project 2 – Wine Bottle Holder
Lay carbon up carbon ply on the convexed surface
Add class plys for strength if needed
Place the core on the center of the convexed surface
Add glass plys for strength if needed
Cover with carbon ply
Peel ply the bag side
Vacuum bag
Demold and trim
Clear coat the bag side for gloss finish