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Composites Manufacturing

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Ahmed Shawky

on 25 October 2014

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Transcript of Composites Manufacturing

Composites Manufacturing
Long Fiber Thermoplastic Matrix Composites.
Hand Laminating
&
Autoclave
Processing of Composites

Filament Winding and
Fiber Placement

Pultrusion.

Liquid Composite Molding.
What are the main components that make up a composite material?
There are two main categories of constituent materials:

- Matrix
- Reinforcement
Introduction to Composites Materials
• What are composite materials?
Composites are made up of individual materials that
bonded together chemically
which are
strong and lightweight.
Structure such as
• Fiber-reinforced polymer
• Honeycomb structure



Hand Laminating:
The depositing of layers is done by hand
Used in low cost components
Resins: Fiberglass, Poly-ester
Autoclave:
The depositing of layers is done by hand
Used in Aircraft industry
Resin: Epoxy
Hand Laminating and Autoclave process
Autoclave
Commonly used in Manufacturing of Aerospace components.
Produce high quality composite components.
Requires a considerable amount of time.
The main steps of the autoclave processing composites are:
Prepregs
Tool (Mold) preparation
Laying up the prepregs
Vacuum Bag
Curing of the part
Prepregs
Prepregging process
Prepregs
Partially Cures resin (30% cross-linked) with fibers.
Prepregs are flexible sticky sheets of fibers about 150 mm thick
Refrigerated shipping- Stored inside -5 °C freezer- have shelf life
Prepregs are available in form of tapes (Unidirectional fibers) or Fabrics (Woven)
Width vary from 25.4 mm- 305 mm
Tool (Mold) Preparation
Mold provides the shape and surface finish of the part.
Curing occurs in high temperature and pressure, so molds required to sustain these conditions
There are generally three categories for tool materials:
I. Reinforced polymers, for low to intermediate temperature ranges
II. Metals, for low to high temperature
III. Ceramics and bulk graphite, for very high temperature

Tool (Mold) Preparation
Release Agent:
This is to facilitate the removal of the part after cure.
Insufficient application of the release agent on the surface of the tool can result in the part sticking to the tool surface.
This may result in damage to both the tool surface and the part.

What are the parts that can be produced?????
Injection molding machine
The main parts of injection molding machine


1. Performs need to be held together by binders. The presence of binders may interfere with the flow of resin to wet the fibers. Binders also need to be dissolved in the resin to avoid the bundling of fibers, which may affect the resulting mechanical properties.
 
2. Performs need to fit well into the tool. For the resin transfer molding(RTM) process, if the preforms do not fit well into the tool such that there is looseness at the peripheries of the preform, liquid resin can run quickly along these easy paths resulting in resin rich areas in the final part.

3. the permeability of the perform depends on many factors, such as the volume fraction of fibers, the compression pressure on the perform, the type of fiber form used, and the stacking sequence of the fibers. The variability of the permeability of the fiber performs makes it difficult to predict the speed of flow of the liquid resin in them. This can result in lack of wetting, voids, and low mechanical properties such as inter laminar shear strength
 
4. the quality of the part can be affected by the presence of voids, dry spots or resin rich areas


The disadvantages of LCM are as follows:
Depending on the fiber volume fraction and the end-use applications,there are many variants of the LCM process as follows:
*Injection molding (IM)
*Structural reaction injection molding (SRIM)
* Resin transfer molding (RTM)

*Vacuum-assisted resin transfer molding (VARTM)
Both mold surfaces is hard
- Advantage: saving money
- Disadvantage: due to low pressure more voids

Seaman composite resin infusion molding process (SCRIMP) one of the mold surface is flexible 

Resin film infusion molding (RFIM) : In this process, instead of injecting resin into the mold, thin films of resin are placed at thebottom of the fiber beds or between different layers of the drypreform. Upon heating and application of pressure, the resin film melts and the liquid resin
permeates into the dry fiber preform.

Mold filling objectives , problems and cures
Objectives
The objectives of mold filling in LCM are to fill the mold completely,

to wet the fibers well, to avoid dry spots and voids, and to avoid modifying

the fiber orientation during the filling process



Problems and Issues Related to Mold Filling
Problems and Issues Related to Mold Filling
Race Tracking
Fiber Washing
Occurrence of Voids
Fiber Wetting
Dry Spots
IN-MOLD CURE
Fundamentals
Optimization of Cure
Cure Problems
Delamination's
Surface Finish
Porous Areas
Incomplete Cure
Introduction
1-Techniques of manufacturing
2-Thermoplastic demands high temp and pressure
3-Permeability is the same
4-Processing need to find new ways to manufacturing


Advantage and disadvantage
Thermoplastic have infinite shelf life
Thermoplastic is more ductile than thermoset
Strain energy is large
Thermoplastic resin can be recycled(can be reheated to take a different form )
Processing time can be fast(heating and cooling can take order of minutes)
for this advantage special technique use to developed thermoplastic composite
Material
Thermoplastic matrix composite are made by combination of fiber material and thermoplastic resin
Types of material:
1. Poly propylene
2. High performance (PEEK)
3. PEAK
4. Poly thermide (PEI)
Strategies of manufacturing
Thermoplastic can be consider to consist two stages:
1. Preliminary
2. Transformed into final composite product

Laying up of prepregs
Determination of number of layers and layer orientation
The number of layers and the orientation of each of the layers can be tailored to meet the mechanical load requirement.
The order in which the layers are stacked on each other is called “Stacking Sequence”
Normally the stacking sequence is written in a laminate code such as [0/90/45/-45]s which can be written in full as [0/90/45/−45/−45/45/90/0]
Laying up of prepregs
The laying up of the prepregs on the surface of the mold consists of not only the laying of the fiber prepregs on the mold, but also the placement of ancillary materials for the following purposes:

• To facilitate the removal of the part after cure (without the
problem of the part sticking to the mold)
• To allow the compaction of the stack of prepregs using vacuum
• To prevent excess resin from running within the plane of the stack
of fibers, which can distort the orientation of the fibers

Laying up of prepregs
• To provide an escape path for volatiles such as water vapor or
gases that are generated during the curing process
• To provide materials that can absorb excess resins that ooze out of
the laminate during the curing and molding process
• To obtain good surface finish on the part



The result of the laying up process is a stack of the prepregs along with
many other layers within a vacuum bag
Laying up process
Before the laying up of the prepregs on the surface of the tool a “Release Agent” needs to be applied; this is to facilitate the removal of the part after curing.

1. Preparation of the mold surface
2. Laying up the stack of prepregs
3. Placement of Bleeder materials
4. Placement of Breather materials
5. Placement of a Caul plate
6. Placement of vacuum bag

Curing and consolidation of the part
The resin needs to be transformed from liquid into solid to make a useful composite
It is important to assure that the fibers maintain their orientation
Sufficient amount of pressure need to be applied
Pultrusion is a manufacturing process that combines many steps in the manufacturing of composites into two steps.
Step a: Beginning from the left-hand side, the fiber tows drawn from fiber racks are routed through a series of guides. The fibers then traverse through a bath of low viscosity resin for impregnation.
Step d: Upon exiting from the resin bath, fibers are collimated into an aligned bundle before entering into a heated die. While inside the die, the following takes place:
—The resin flows and wets the fibers.
—The ensemble of fibers and resin is compacted.
—The resin cures and the fiber/resin system becomes solid.
The state of development of pultrusion as a process manufacturing is still in the experimental stage.

This is due to the integration of many steps into the process which makes it complex.
The permeability of the resin into the fiber bed varies greatly with the fiber bundles
and also varies with the degree of compression of the fiber bed.
The rate of reaction of the resin is rapid due to the fast production rate.
Pultrusion can produce parts with low cost using low-cost materials such as glass and polyester.
MATERIALS
1. Fibers
I. Unidirectional Rovings

• Fiberglass is the most commonly used fiber for pultrusion
• Unidirectional fibers are the least expensive reinforcements available
• used in structural applications where loading is highly oriented along the length of the profile
• Unidirectional loading minimizes friction drag in the die, provides the highest pulling strength possible, and simplifies the design and fabrication of forming guides at the entrance of the die.
• Parts constructed this way might have unacceptable resistance to crushing or splitting parallel to the fiber direction.
• Some means of providing strength in the transverse direction is often mandatory

II. Woven and Nonwoven Broad Goods
• Lowcost commercial pultrusions made of unidirectional glass rovings often include inexpensive forms of nonwoven broad goods called continuous strands and chopped strand mat
• The random orientation of these materials provides some degree of off-axis strength and stiffness enhancement at very low cost.
• Woven materials used in the pultrusion process must be placed between more stable forms such as layers of unidirectional rovings.

2. Resins
• The necessary characteristics for a resin to be used to make pultruded products are that it have low viscosity and that gel time and cure time are short to allow for the high rate of production.
• The resin normally used to make pultruded products is polyester resin, due to its low cost and low viscosity.
• When better corrosion resistance is required, vinyl ester resins are used.
• When a combination of superior mechanical and electrical properties is required, epoxy resin is used. Epoxies are three to six times more expensive than polyester and needs more time to be cured.

FACTORS AFFECTING THE PULTRUDABILITY OF A COMPOSITE COMPONENT:
Two important characteristics affecting the pultrudability of a composite
product are:

• the pulling force required to move the product steadily through the system and the pulling speed
• the pulling speed determines the productivity of the process.

Common types of composite materials traditionally used in aircraft?
Fiberglass
Carbon fiber
Fiber-reinforced matrix systems
Or A combination of any of the above
Common composite materials used in aviation are
Fiberglass
lightweight
extremely strong
robust material
strength properties lower than carbon fiber, less stiff, less expensive
Carbon fiber
high stiffness
high tensile strength
low weight
high chemical resistance
high temperature tolerance
low thermal expansion
high strength-to-weight ratio
is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass
is an extremely strong and light fiber-reinforced polymer which contains carbon fibers.
Fiber-reinforced matrix systems
Fiber-reinforced composites are composed of axial particulates embedded in a matrix material.
The objective of fiber-reinforced composites it to obtain a material with:
high specific strength
high specific modulus
E.G: kevlar

• Fairings
• Flight control surfaces
• Landing gear doors
• Leading and trailing edge panels on the wing and stabilizer
• Interior components
• Floor beams and floor boards
• Vertical and horizontal stabilizer primary structure on large aircraft
• Primary wing and fuselage structure on new generation large aircraft
• Turbine engine fan blades
• Propellers
Applications of composites on aircraft include:
Which part of the aircraft can you find composite materials?
PRELIMINARY MATERIAL COMBINATIONS (PMCs):
In the PMC, it is essential for the matrix to be in the vicinity of the fibers. This is important to reduce the time and pressure required to get the Matrix to get to the fibers during the final product fabrication.The approaches used will be discussed below
1. PRINCIPLES of the MANUFACTURING OF COMPOSITE MATERIALS-
Suong V. Hoa
References:
Department of Mechanical and Industrial Engineering
Concordia University, Quebec, Canada
Presentation Program:
PREZI.Com
Filament Winding:
Filament winding is a process to make a comosite structures such as pressure vessels, storage tanks or pipes
- composite pressure vessels have light weight and high strength

Applications
Oxygen tanks
Used in A/C
Mountain climber
Drive shafts
Winding Process
The operation of filament windings is the reverse of the conventional machining of milling on a lathe

A) In milling process
B) In filament winding
Types of winding:
Polar
Helical
Circuit
Pattern
Layer
Loop
Longitudinal
Combination
Materials
1. Reinforcements
Nearly all filament winding for making pipes or low-pressure vessels
is conducted with continuous E glass roving as reinforcement.
2. Resins
The major matrix system for filament windings are based on epoxy polyester or viny-ester resins
Epoxy resins for filament windings are essentially the same as laminating
Epoxy resins have lower cost and balance of physical and chemical properties
Mandrels
Extractable
Collapsible
Breakable
Dissolvable
Fiber Motion
During processing, the fibers may move causing a change in fiber tension and in fiber position.
Fiber placement process is a process similar to filament winding.
Filament Winding:
Fiber tows are subjected to tension while they are being placed on to surface of mandrel
Used for wet winding and dry winding
Fiber Placement:
Push towards the surface of mandrel
Used for prepregs or tapes
INTRODUCED BY:
Autoclave
Injection molding

The most process used to produce plastic parts
Hinged
Spring
Thread
Holes
2. ASAS Composites Prezi
http://prezi.com/m59uvhcgu57u/asas-composites/
Full transcript