1. Investigation of Flax Fibre
Reinforced Hybrid Composites
for Use in a Roll Cage
Renette de Villiers
Supervisor: Dr H. Abhyankar
Cranfield University, College Road, Cranfield, Bedfordshire, MK43 0AL, UK
Dr Rishi Abhyankar h.a.abhyankar@cranfield.ac.uk
Renette de Villiers renettedev@gmail.com
www.motorsport.cranfield.ac.uk
Introduction Aim and Objectives
Conclusions
The aim of this study is to evaluate the feasibility of
using carbon/flax hybrid composite in a roll cage to
replace steel. In order to achieve this, the study
includes physical material tests, FEA on the roll cage
as well as full car crash FEA.
Roll Cage FEA
0 5 10 15
0
10
20
30
40
50
60
70
80
90
100
110
Time [s]
Displacement[mm]
Front Displacement
Steel
Hybrid Composite
Maximum Allowed
0 5 10 15
0
5
10
15
20
25
30
35
40
45
50
55
Time [s]
Displacement[mm]
Rear Displacement
Steel
Hybrid Composite
Maximum Allowed
All roll cages used for racing must pass
two FIA quasi-static tests where loads are
applied to the cage. In the rear test
(pictured) the deflection must be less than
50mm and the front less than 100mm.
This was simulated using LS Dyna to
ensure the hybrid roll cage will pass the
necessary load tests.
Full Car FEA
No roll cage Steel roll cage Hybrid roll cage
In order to evaluate the performance in comparison to
steel, full car crash FEA was done to simulate a rollover
situation. It was found that the steel cage yielded under
the load, where the hybrid composite roll cage fractured
in eight places due to its brittle behaviour. Using a hybrid
composite roll cage is therefore not feasible.
Material Testing
0 0.05 0.1 0.15 0.2 0.25
0
20
40
60
80
100
120
Displacement [m]
Force[kN]
Material comparison: Force vs Displacement
Carbon
Hybrid
Flax
Sled tests were done on the carbon fibre, flax fibre and hybrid composite samples. In
the hybrid composite sample (50% carbon fibre, 50% flax fibre), the carbon fibre was
found to dominate the performance. The hybrid composite thus closely matched the
performance of the carbon fibre samples.
Material Test
FEA
Material tests done were
simulated using LS Dyna.
A good correlation was
not found between the
FEA and physical tests,
and this leaves potential
for further work.
After simulations and material tests were completed it is concluded that carbon/ flax fibre hybrid composite is not feasible for use in a
roll cage. However, the material does show potential for use as a lighter and cheaper alternative to carbon fibre in other applications.
Roll cages have been mandatory in motorsport since 1971, and the use of
steel in roll cages has been required since the mid-1970s. Even though
other materials are not currently allowed, there is a need to investigate
alternative materials for the possibility of reducing weight without reducing
safety. In this study, flax fibre reinforced composites are considered.
Carbon fibre Flax fibre