Crashworthiness of Axis Symmetric Composite Structures

for Automotive ApplicationsMaximillian D X Dixon

www.bris.ac.uk/composites

2/9Crumple Zone

Source: http://www.motortrader.com.my/news/euroncap-5-stars-for-2014-mazda3/mazda-skyactiv-structure/

Source: http://www.seriouswheels.com/pics-2008/nopq/2008-Porsche-911-GT2-Body-shell-1280x960.jpg

3/9Crush Response Metric

Displacement

Load

Progressive FailureCatastrophic Failure

DisplacementLo

ad

4/9

Progressive Folding1

Progressive Fragmentation1

• Global Buckling (Euler Buckling),• Progressive Folding,• Progressive Crushing,

– Progressive Splaying,– Progressive Fragmentation.

Progressive Failure Modes

Progressive Splaying1

1. Source: D Hull, 1990, “A Unified Approach to Progressive Crushing of Fibre-Reinforces Composite Tubes”.

5/9Fracture Toughness

Matrix Material

Interlaminar Fracture Toughness GIC (kJ/m2)

PEEK 1.6-2.4PEI 1.0-1.2PI 0.8-0.9Epoxy 0.2-0.3Source: G C Jacob, 2002, “Energy Absorption in Polymer Composites for Automotive Crashworthiness”.

Source: G C Jacob, 2002, “Energy Absorption in Polymer Composites for Automotive Crashworthiness”.

6/9Monolithic StructuresContributing factors include:Fibre Type, Matrix Type, Cross Section & Fibre Architecture

Material SEA (kJ/kg)Steel & Aluminium 15-30

Carbon/Epoxy 80Glass/Epoxy 60

Carbon/PEEK 194Carbon/PEI 155Carbon/PI 131Carbon/Epoxy 110

180

190

200

210

220

230

240

0 5 10 15 20 25S

EA (

kJ/

kg)

Fibre Angle (°)Source: G C Jacob, 2002, “Energy Absorption in Polymer Composites for Automotive Crashworthiness”. Source: S Ramakrishna, 1995, “Energy Absorption Behaviour

of Carbon Fiber Reinforced Thermoplastic Composite Tubes”.

7/9Off Axis Loading

0

5

10

15

20

25

30

35

0 5 10 15 20 25

Sp

ecif

ic E

ner

gy

Ab

sorp

tio

n

(kJ/

kg)

Loading Angle (°)

Carbon Glass HybridSource: V M Karbhari, 2003, “Energy absorbing characteristics of circular frustra”.

Source: F. Tarlochan, 2013, “Design of thin wall structures for energy absorption applications Enhancement of crashworthiness due to axial and oblique impact forces”.

8/9Sandwich Structures• Potential improved axial and off axis loading performance

• Monolithic SEA - 10.3 kJ/kg (no core)• Sandwich SEA - 30.3 kJ/kg (foam core)

• Further performance enhancement through use of “tied core” structures

Source: F. Tarlochan, 2012, “Advanced composite sandwich structure design for energy absorption applications: Blast protection and crashworthiness”.

Source: G. Pitarresi, 2005, “A comparative evaluation of crashworthy composite sandwich structures”.

9/9SummaryThe Efficient Energy Absorber should include:

•PEEK matrix•Carbon/glass Hybrid laminate•Frustra (Conical)•Hexagonal cross section•15°off axis fibre angle•Foam core