Materials 2 Avoiding Mechanical Failure Week 8 Demo Personal body - - PowerPoint PPT Presentation

Materials 2 Avoiding Mechanical Failure Week 8 Demo – Personal body armour

Ned Kelly’s armour in the State Library of Victoria by Chensiyuan

Personal armour has always been a trade-off between protection and movement

http://en.wikipedia.org/wiki/File:Lorica_Hamata.jpg by Greatbeagle

Bronze armour from ~ 300BC

Steel armour ~ 1550 Hardened leather scale armour –

samuraiantiqueworld

Assignment 2

• Need to understand the application to accurately to do the first two dot points.
• If body armour was the topic – then how does it protect a person?

Need to understand what you are trying to protect against slow motion bullet impact

Some things to think about

• Kinetic energy – this energy has to be dissipated

before it reaches the target – either by armour penetration or through projectile deformation

• Soft versus hard projectile materials
• Global versus local damage to the armour

Modern materials – aramid fibre

• Tensile strength in the excess of

3500 MPa

• Young’s modulus ~ 130 Gpa
• Often produced as a woven fabric

Some things that are important

• Modulus and tenacity (breaking force

divided by denier) of the fibre

• Strain wave velocity - (fibre

modulus/fiber density)*1/2

• Friction between fibre and fibre (and

fibre and projectile). Can coat fibres to increase friction.

Lightweight ballistic composites by Ashok Bhatnagar (2006)

Local versus global damage

Modern materials – hybrid armour

Very common to put a hard ceramic plate with a woven fibre backing. What do you think the roles of each are?

Research literature

• Where to find it
• How to quickly assess it
• What parts are important
• What is the paper I find doesn’t give me everything I need?
• Citing the right way

http://www.nature.com/ncomms/journal/v3/n10/full/ncomms2166.html