Post on 16-Apr-2017
Synthetic biology for transparent materials
CDE themed competition
12/9/2016
OFFICIAL Crown copyright 2016 Dstl
12/9/2016
How can synthetic biology help address
intractable defence challenges?
Crown copyright 2016 Dstl OFFICIAL
Priorities in the competition
12/9/2016
Synthetic biology
novelty, quality,
impact, risk, value
Incremental, vague,
outside scope, no
defence application
identified
Challenge 1: production and
characterisation of novel
transparent materials
Challenge 2: adhesives and
interlayer materials compatible with
transparent materials
Utilising synthetic biology for transparent materials for
Defence and Security
Crown copyright 2016 Dstl OFFICIAL
Synthetic biology for transparent materials
• transparent armour
• functional transparent materials for sensor protection
• adhesives for interlayer materials
OFFICIAL 12/9/2016
Crown copyright 2016 Dstl
Transparent armour
• uses of transparent armour
• some fundamentals of armour performance
• why transparent armour materials are inferior to opaque armour
materials
OFFICIAL © Crown copyright 2016 Dstl
Transparent armour
Recurring theme …
• interfaces have significant effects both optically and ballistically
• factors that enhance ballistic performance may degrade optical
performance
• some factors may have both positive and negative influence
OFFICIAL © Crown copyright 2016 Dstl
Transparent armour
Currently has relatively poor ballistic performance • soda-lime glass
• borosilicate glass
• polycarbonate
Performance worse than opaque armour
Potential transparent armour materials are expensive • sapphire
• aluminium oxynitride
• magnesium aluminate spinel
• lithia glass ceramic
Surface finishing is expensive
OFFICIAL
© Crown copyright 2016 Dstl
Transparent armour
Particularly a problem for • logistic vehicles
• VIP cars
• protected patrol
• rotorcraft
• eye and sensor protection
Extra weight of transparent armour results in
• raised centre of mass = degraded handling
• increased cost of ownership
• reduced payload
• increased logistic burden
OFFICIAL © Crown copyright 2016 Dstl
OFFICIAL © Crown copyright 2016 Dstl
Vehicle transparent armour
Armoured saloon (CSAP)
2.3-2.6 tonnes
APV 1.5
4.4 tonnes
SAXON
11 tonnes
SNATCH
3.6 tonnes
TAVERN
5.4 tonnes Challenger 2
~65 Tonnes
Priorities
Armoured fighting vehicles • transparent armour covers a very small area • protects periscopes, cameras, sensors • primary purpose – to provide optical access • enhancements valuable only if they can preserve
optical function
OFFICIAL © Crown copyright 2016 Dstl
Priorities
Logistic and support vehicles
• transparent armour may cover a large area • much larger percentage of the platform weight • raises centre of mass • protects the highest value component – the crew
OFFICIAL © Crown copyright 2016 Dstl
Priorities
Rotorcraft, covert vehicles, aircraft • weight is critical, situational awareness is
critical, protection is critical
Eyes • valuable asset • “platform” cannot support large weight
Sensors • multiple-bandwidth
OFFICIAL © Crown copyright 2016 Dstl
© Crown copyright 2013 Dstl
09 December 2016
Priorities
• weight
• thickness
• material choice
– multiple bandwidth – adhesives and surfaces
• cost – basic material – processing
OFFICIAL © Crown copyright 2016 Dstl
Impact induced stress waves
By divergence or interaction with
• inclusions • voids • defects • interfaces • boundaries • surfaces
A compressive wave can generate
• shear • tension
OFFICIAL © Crown copyright 2016 Dstl
Impact induced stress waves
Stress wave conversion at an interface
Stress wave propagation in hard faced armour
Ductile backing
Ceramic or glass
Glueline
Impact induced stress waves
OFFICIAL © Crown copyright 2016 Dstl
CERAMIC TILE OR GLASS
ADHESIVE
BACKING
Bad design Good design
Hard faced armour
OFFICIAL © Crown copyright 2016 Dstl
Optical effects
• optical effects may take place at macroscopic or microscopic interfaces or inclusions
• any process that removes optical energy from the original optical path contributes to “opacity”
Reflection Refraction
Absorption
Scattering
OFFICIAL © Crown copyright 2016 Dstl
Opaque vs transparent
Good armour materials are hard and strong
Such materials are often network covalent solids
• often have anisotropic crystal structures
• large single crystal pieces expensive and may fail through single crack propagation
• practical materials often multi-crystalline
OFFICIAL © Crown copyright 2016 Dstl
Opaque vs transparent
Materials can be enhanced with toughening
mechanisms • often crack-tip stopping mechanisms
• rely on interfaces and inclusions
Interfaces, inclusions and agglomerates give rise to optical reflection, refraction, scattering and absorption
• good armour materials tend to be opaque
OFFICIAL © Crown copyright 2016 Dstl
© Crown copyright 2016 Dstl
Transparent armour
Conventional transparent armour Transparency reduction as
a result of impact
OFFICIAL
Material properties
Material Density (kg/m2) E (GPa)
Hardness
(kg/mm2)
HARD Sapphire 3980 420 2200
Aluminium oxynitride 3700 317 1850
Magnesium aluminate spinel 3590 268 1520
Lithia glass ceramic 2530 101 803
INTERMEDIATE Fused Silica 2500 73 460
Float glass 2495 59 540
Borosilicate 2225 54 580
SOFT Polycarbonate 1200 2.35 <20
Polyvinyl butyral PVB 1100 2.1 <20
© Crown copyright 2016 Dstl OFFICIAL
Spalling behaviour of polycarbonate backing
Armour piercing projectile
Glass ceramic
Polyurethane glue
Polycarbonate
OFFICIAL © Crown copyright 2016 Dstl
Armour piercing projectile
Glass ceramic
Polyurethane glue
Polycarbonate
Reduction of maximum stress at armour/backing interface
OFFICIAL © Crown copyright 2016 Dstl
Glass ceramic
Polyurethane
Polycarbonate 0
0.5
1
1.5
2
2.5
3
3.5
Max
stress
GPa
1 2 3 4
No. of layersGlass ceramic
Polyurethane
Polycarbonate
Transparent armour
• choice of transparent protective materials is small
• factors that enhance protection can degrade transparency
• generally heavier than equivalent opaque armour
• more expensive than opaque armour
• tends to protect important parts
• improvement would be highly beneficial
OFFICIAL © Crown copyright 2016 Dstl
The role of synthetic biology?
• we need strong, tough transparent systems
– across multiple bandwidths
– with managed reflectance
• biological systems already do this
– nacre type systems are inherently tough
– templating can control fine structure
– many biological examples of morphological reflectance management
© Crown copyright 2016 Dstl OFFICIAL
The role of synthetic biology?
• composite transparent systems need adhesives and coatings
– synthetic biology has already shown capability here
• current choice of transparent armour materials is small
– synthetic biology can expand our material choice
• grinding and polishing is expensive
– can synthetic biology produce net shape and finished surface?
OFFICIAL