Family Trees: Organising Materials and Processes into Trees

1. Family Trees: Organising Materials and Processes into Trees

2. Introduction to Materials and Processes • A successful product – one that performs well, is good value for money and gives pleasure to the user – uses the best materials for the job, and fully exploits its potential and characteristics • Materials selection is not about choosing a material, but a profile of properties that best meets the needs of the design • Material and process are interdependent • Materials and processes are grouped into families; each family has a characteristic profile, the “family likeness,” which is useful to know when selecting which family to use for a design

3. Six Families of Materials • Members of a family have common features • Similar properties • Similar processing routes • Similar applications Hybrids are a combination of materials from other families

4. Examples of Different Material Families

5. The taxonomy of the kingdom of materials and their attributes. Computer-based selection software stores data in a hierarchical structure like this.

6. Ceramics • Stiff – high E • Hard • Abrasion resistant • Good high temperature strength • Good corrosion resistance • Brittle • Glasses • Hard • Corrosion resistant • Electrically insulating • Transparent • Brittle – low K1c

7. Polymers • Light – low ρ • Easily shaped • High strength per unit weight • Lack stiffness – low E (50X less than metals) • Properties highly sensitive to pressure • Elastomers • Lack stiffness – low E ( 500 – 5000X less than metals) • Able to retain initial shape after being stretched • Relatively strong and tough

8. Metals • Tough – high K1c • Stiff – high E • Ductile • Wide range of strengths depending on composition and processing • Thermally and electrically conductive • Reactive – low corrosion resistance • Hybrids • Expensive • Difficult to shape and join • Properties dependent on combination of materials

9. The Classes of Processes

10. Classifying Processes Choice of process is based on design requirements: Material Shape, dimensions, and precision Number to be made Primary process creates shapes Secondary process modifies shapes or properties

12. Primary Shaping

13. Secondary Processes

14. Joining

15. Surface Treatments

16. Process selection involves matching these attributes to the requirements of the design

17. The taxonomy of the process kingdom, showing certain attributes of the joining and surface treatment families

18. Effects processing can have on material properties Soft, stretchy rubber becomes hard and brittle when vulcanized Annealing a metal increases its ductility Glass becomes bullet-proof through a specific heat treatment Electroplating improves corrosion resistance

19. Material Property Charts (“Ashby Charts”) Gives an overview of physical, mechanical, and functional properties Reveal aspects of physical origins of properties Tool for optimized selection of materials

20. Bar Chart of Modulus Reveals the difference in stiffness between families

21. EXAMPLE In a cost cutting exercise, one designer suggests that certain die-cast zinc components could be replaced by cheaper moulded polyethylene (PE) components with the same shape. Another designer is concerned that the PE replacement might be too flexible. By what factor do the moduli of the two materials differ? Answer: The bar chart above shows that the modulus of PE is less, by a factor of about 100, than the modulus of zinc alloys. The concern is a real one.

22. Bubble Chart: Modulus and Density Logarithmic means that the scale goes up in constant multiples, usually ten (a “decade”).

23. EXAMPLE Steel is stiff (large E) but heavy (large ρ). Aluminum alloys are less stiff but also less dense. Once criterion for lightweight design is a high value of E/ρ, defining materials that have a high stiffness per unit weight. What is the relative value for aluminum versus steel? What about carbon-fiber reinforced plastic? (CFRP)

24. Answer: The E/ρ chart answers the question. All three materials are on it. Materials with equal values of E/ρ lie on a straight line with slope=1 (it is a log-log chart). Materials with higher values lie in the top left of the line, and materials with lower values lie to the bottom right of the line. For aluminum alloys, a line drawn through them goes almost exactly through the steels: the two materials have nearly the same value of E/ρ. CFRP however has a much higher value than either aluminum or steel.

25. Example for ABS of typical computer data sheet CES contains numeric data, text, and image-based information for materials and processes

26. Example of Process data sheet Part of a record for injection molding. The image shows how it works, and the numeric and Boolean data and text document its attributes

27. Computer based resources for Materials CES Edu (www.grantadesign.com) - license required). A comprehensive suite of databases for materials and processes with editions for general engineering, aerospace, polymer engineering, environmental design, industrial design. Matbase (www.matbase.com – soon to be www.matbase.nl – free). A database of the technical properties of materials originally from the Technical University of Denmark. Matdata (www.matdata.com- limited access is free, full access with license). A well documented database of the properties of metals. Material (www.material.nl- free) A databased aimed at industrial design, with high quality images of some 2000 products. Material Connexion (www.materialconnexion.com-license required). A materials library for industrial design with records on 7000 materials each with an image, description and supplier. Matweb (www.matweb.com-limited access free, full access license). A large database of the engineering properties of materials, drawn from suppliers' data sheets. Rematerialise (www.rematerialise.org- free) A database of 'sustainable' materials chosen because they are derived from renewable (biological) materials or use recycled materials.