8.6 Composite materials
Specification content
The working properties, stock forms and sizes, common uses and environmental impact of the following:
– foam core/foam board
– foil backed and laminated card, e.g. Tetra Pak®
– manufactured boards ○ chipboard ○ engineered wood ○ medium density fibreboard (MDF) ○ plywood ○ blockboard
– fibre reinforced materials ○ glass fibre reinforced plastic (GRP) ○ carbon fibre reinforced plastic (CFRP).
A composite material is a material that combines two or more materials with different properties
Learning Outcomes
By the end of this unit you should have developed a knowledge and
understanding of:
the specific names and classifications of composites
what constitutes a composite material
the performance characteristics of different types of composites
why different types of composites are suitable for different applications
common composite based products
the benefits of using composite materials
Introduction - Composite materials
A composite is a mixture of materials combined to enhance their individual properties.
Composites can be put in three main categories.
Composites generally fall into one of three groups; fibre based composites, particle based composites and sheet based composites.
The most important of these for your studies are the fibre reinforced composites since they are most commonly used in the manufacture of products!
Fibre Based
Reinforced with fibres
GRP, CFRP
Particle based
Reinforced with particles
Concrete, GRC, Cermets
Sheet based
Boards made from wood pulp, chips or layers
Chipboard, Conti board, MDF, Plywood, Stirling board
The term ‘man-made board’ is sometimes used to describe manufactured boards such as MDF and Chipboard where wood has been combined with resin to form a ‘new’ material - These type of boards have increased stability and resistance to warping etc. and have equal strength in all directions unlike natural timber.
Fibre-based composites
These composites have the following characteristics:
good strength to weight ratio.
resistance to corrosion.
good fatigue resistance
low thermal expansion
Glass Fibre or Glass Reinforced Plastic (GRP)
Glass Fibre shapes are made by ‘laying up’ as in the diagram.
Glass is spun to produce a fibre which is then coated to aid bonding to the resin.
The fibres of glass are available in a variety of thicknesses from coarse to very fine.
The Polyester Resin used is quite brittle on its own and the glass fibres are relatively useless without the resin to bind them together.
The composite material produced is called Glass Reinforced Plastic or GRP.
A mould is required for GRP and these can be produced quite cheaply but their surface can often affect the final quality of the GRP shell.
Inserts such are reinforcing struts and mounting plates can be included while the material is being ‘laid up’.
Violin and case
boat hull
boat hull
Surf board
Carbon Fibre Reinforced Polymer (CFRP)
Carbon Fibre Reinforced Polymer (CFRP) such as matting has become popular in the production of F1 car bodies, tennis racquets and other performance equipment.
Carbon fibres are woven into a matt which is cut to shape. This is what gives carbon fibre its distinctive look.
This is then placed in a mould where it is impregnated with resin and forced into shape.
The mould parts are then baked at 170 degrees C for up to 8 hours to promote the rigid cross links in the resin.
Sheet-based composites
These have been covered in the Woods section as they are generally considered manufactured boards.
Plywood
Hexaboard
Contiboard
Paperboard based composites
Foam core/foamboard
Foam core, also known as foam board, is a lightweight and versatile material commonly used in various applications. It consists of a foam core sandwiched between two outer facing sheets, typically made of paper. This construction makes it easy to cut, shape, and mount, making it a popular choice for both professional and DIY projects.
Positives:
Lightweight: Easy to handle and transport.
Easy to cut: Can be cut with a utility knife or specialized foam board cutter.
Smooth surface: Provides a good surface for mounting prints, photos, and other materials.
Affordable: Generally inexpensive compared to other mounting options.
Negatives:
Denting and crushing: The foam core can be easily dented or crushed, especially with rough handling.
Warping: Can warp or bend over time, especially in humid environments.
Not archival: Standard foam core is acidic and can damage artwork over time.
Typical Uses:
Mounting: Photos, posters, artwork, and other flat materials.
Signage: Creating signs, displays, and promotional materials.
Model making: Architectural models, dioramas, and prototypes.
Craft projects: DIY projects, school projects, and arts and crafts.
Environmental Impact:
Foam core is typically made from polystyrene, a type of plastic that is slow to degrade and can contribute to environmental pollution. While some manufacturers are starting to use recycled materials in their foam core production, it is still important to dispose of foam core responsibly. Some recycling facilities may accept foam core, but it is best to check with your local waste management provider for specific guidelines.
foil backed and laminated card
Foil-backed and laminated card, like Tetra Pak, is a versatile packaging material made from layers of paperboard, polyethylene, and aluminum foil. This combination creates a sturdy, lightweight, and protective barrier, making it ideal for various applications.
Positives:
Durability: The multiple layers provide strength and resistance to tearing and punctures.
Protection: The foil layer acts as an excellent barrier against oxygen, moisture, and light, preserving the contents and extending shelf life.
Lightweight: The material is relatively light, making it easy to transport and handle.
Printable: The paperboard layer provides a good surface for printing, allowing for attractive branding and labeling.
Negatives:
Recyclability: Separating the different layers for recycling can be challenging, leading to lower recycling rates compared to other materials.
Environmental impact: The production of aluminum foil is energy-intensive and can contribute to environmental concerns.
Examples of use:
Food packaging: Milk cartons, juice boxes, and other liquid containers.
Pharmaceutical packaging: Blister packs for medications.
Cosmetic packaging: Sachets for creams and lotions.
Environmental impact:
While foil-backed and laminated card offers excellent protection and convenience, its environmental impact is a concern. The difficulty in recycling and the energy-intensive production of aluminum contribute to its environmental footprint. However, advancements in recycling technology and the use of recycled materials are helping to mitigate these concerns.
Applications for composites
Kitchen Knives
Traditionally made from metal, knives can now have ceramic edges which result in a sharper and more durable cutting edge.
flooring
Traditionally made from wooden planks, flooring is now made from sheets of chipboard or MDF due to stability and low cost.
bicycle frames
Once made of Steel, then Aluminium alloy, frames on more expensive bicycles are now made of Carbon fibre. The first example of this was the Boardman bicycle which helped its rider win gold at the 1992 Barcelona Olympics. Carbon fibre frames are now common but have a higher price point than aluminium frames.
Summary
composites are a mixture of materials combined to improve their properties.
manufactured boards such as Plywood and MDF are composites because they are a combination of wood and resin.
composites generally fall into one of three groups; fibre based composites, particle based composites and sheet based composites.
fibre based composites include Carbon Fibre, GRP (glass reinforced plastic) and GRC (glass fibre reinforced concrete)
particle based composites include concrete and cermet
sheet based composites include manufactured boards.
composites are now being used to replace traditional materials such as timber and metal.