Week 4

Week 4 - Selection of materials For this week we are given an assignment that helps to recap about our module, Material For Design, MFD which is about the classification of materials, material properties and testing and the selection of materials.

MFD and ICPD are related to each as it consists of three interrelated problem:

1. Selection of materials

2. Specification of a shape

3. Choosing a manufacturing process

We will be going more in-depth about the selection of materials:

• The objective of this process is to identify the various materials with properties that fulfills the functional requirements of the product. Hence, doing a comparison of the materials and deciding on the most suitable material whereas there will be trade-offs between the requirement and numerous constraints.

These factors are contributed by the different material properties such as mechanical, physical, thermal, magnetic, fabrication and environmental properties.

• Stages in materials selection process:

1. Define materials & Requirements for the design

2. Selection and evaluation of suitable materials using COWS decision matrix

3. Choose the most economical material

• COWS Decision Matrix

1. Listing the material requirements for the design

2. Selection and evaluation of suitable materials

3. Choose the most economical material

Classification of materials

1. Natural materials:

• A natural material is any product or physical matter that comes from plants, animals, or the ground. Natural materials include stone, glass, wood, cotton silk and many more.

2. Metals & Alloys:

• Its properties are that it has a high electrical and thermal conductivity, and that it has high stiffness and strength.

3. Ceramics:

• They are inorganic compounds and clay-based materials, and its properties are that it is brittle, hard, bad conductors of electricity and heat.

Some examples:

• Glass

• Domestic Ceramics (porcelain, cement)

• Engineering ceramics (Alumina, Carbides)

• Natural Ceramics (Rocks)

4. Polymers:

• A polymer is a substance or material consisting of a long chain of molecules, composed of many repeating monomers bonded together. They can be classified into three main categories: thermoplastics, thermosets, elastomers.

• Thermoplastics: A thermoplastic is a material, usually a plastic polymer, which becomes more soft when heated and hard when cooled. Examples of thermoplastics are acrylic, polyester, nylon and teflon.

• Thermosets: Thermosets are polymers in which a crosslinking reaction occurs promoting chemical bonding between macromolecular chains. Unlike thermoplastics which can be heated and cooled multiple times, Thermosets will irreversibly harden upon heating. Examples are epoxy resin, fiberglass, vinyl ester resin and cyanate ester

• Elastomers: Elastomers are special polymers that are very elastic. Examples include Natural rubber as well as Nitrile Rubber.

5. Composites:

• A composite material is a material which is produced from two or more materials. These materials have notably different chemical or physical properties and are merged to create a material with properties unlike the individual elements. Examples of composite materials include Fiberglass and Carbon Fiber.

Material Selection

The “Right” material is selected based on:

• Design Requirement

• Manufacturing Process

• Environmental Considerations

• Availability

• Cost

To choose the right materials we can use the COWS matrix

• Criteria: The desired properties of the product

• Options: The different types material suitable to be the product’s material

• Weightage: Scoring the different criteria based on importance

• Score: All the scores will be added up and the one with the highest score will be the selected material.

Assignment given:

Material: Cap and Body of Water bottle

COWS Decision Matrix

NA: Not applicable and hence it will be given a rating of 1

COWS Decision Matrix (Economical)

NA: Not applicable and hence it will be given a rating of 1

Reflection

In week 4, we were given an assignment to help us recap on the topic of MFD which is related to ICPD. We were given online resources on Blackboard to help refresh our minds on MFD, which consists of classification, properties, testing and selection of materials. We classified the materials to various groups such as natural, metals & alloys, ceramics, polymers and composites. Some examples for the properties of materials are mechanical, physical, thermal, magnetic, fabrication and environmental properties. Through the selection of materials, we were able to determine which material is most suitable for our assigned product by using the COWS decision matrix.

Firstly, we listed the various materials and stated the requirements for the product. We stated the functions, constraints and objectives of the product to help out with the selected criteria and various materials with an environmentally conscious mind. Secondly, we selected and evaluated the materials. We selected the following criteria of density, impact resistance, toxicity, carbon footprint and melting point to aid in our evaluation. Additionally, we chose low density polyethylene, borosilicate glass and polyvinyl chloride to be considered as the materials used for the product. From there we got a total rating of 270, 200 and 200 each respectively. Lastly, we evaluated the most economical material and chose the most suitable material for the product. We got a rating of 220, 180 and 200 for low density polyethylene, borosilicate glass and polyvinyl chloride respectively. Therefore, from these ratings, we chose low density polyethylene as our most suitable material.

Done by:

Syafiq Bin Baharun