A study on the fatigue strength of fiber reinforced hybrid epoxy composites was evaluated in this paper. The fiber metal laminates are hybrid composite materials are made from interlacing layers of thin metals and fiber reinforced plastics. The flexural strength of hybrid fiber metal composites was investigated from the three point bending test in accordance with ASTM D790-03 at various hybrid ratios of sequence layer in FML composites. The Glass fiber, Kevlar fiber and aluminum were taken for laminating the composite and reinforced with epoxy matrix. The adhesion property of fiber metal composites was enhanced by modified aluminium surface treatments and kevlar surface is treated with epichlorohydrin re-treatment. The interfacial fracture toughness were investigated from ASTM D5528-01. The flexural modulus and strain to failure results have been showed for various hybrid combinations, which have more effect on interlaminar strength of GARALL composites and improved fatigue life of leaf spring

1. Material
science Design and Fatigue Failure
Analysis of Kevlar
Composite Leaf Spring

2. Abstract
A study on the fatigue strength of fiber reinforced hybrid epoxy composites
was evaluated in this paper. The fiber metal laminates are hybrid composite
materials are made from interlacing layers of thin metals and fiber reinforced
plastics. The flexural strength of hybrid fiber metal composites was investigated
from the three point bending test in accordance with ASTM D790-03 at various
hybrid ratios of sequence layer in FML composites. The Glass fiber, Kevlar fiber and
aluminum were taken for laminating the composite and reinforced with epoxy
matrix. The adhesion property of fiber metal composites was enhanced by modified
aluminium surface treatments and kevlar surface is treated with epichlorohydrin re-
treatment. The interfacial fracture toughness were investigated from ASTM D5528-
01. The flexural modulus and strain to failure results have been showed for various
hybrid combinations, which have more effect on interlaminar strength of GARALL
composites and improved fatigue life of leaf spring.

3. Fiber metal Laminate 01
Hybrid GARALL 02
Leaf spring03
Three questions:
1. What is FML?
2. What is hybrid GARALL?
3. Why leaf spring?
3
Important
keywords

4. What is FML?
 First introduced in late seventies at Delft
University of Technology.
 Built up from interlacing layers of thin
metals and fibre reinforced adhesives.
 Combining two materials to form a hybrid
composite structural material to overcome
disadvantages of both materials.

5. FML provide favorable mechanical properties
1. High strength
2. Low density that lead to weight savings
3. Fatigue insensitivity show excellent damage
tolerance
Why FML?
Bridge between
Practice and theory

6. What is Hybrid
GARALL?
ARALL (Adv) + GLARE(Adv)

7. Pre treatment requirements
Surface
properties
Interlaminar
fracture
toughness
To enhance
fatigue life

8. Step 01 Step 02
In ECH grafting surface
modification, the Kevlar fabric
was initially immersed in a
solution of KOH (1%) at room
temperature for 2 hours
It is the initiator for grafting with
ECH and hydrolyzation of the
amino bond and –COOK groups
were introduced to the Kevlar fiber
surface
Step 03
after which kevlar fiber was
grafted in epoxy chloropropane at
80 °C for 6 h During the surface
modification treatment
Step 04
the acetone was added with ECH to
prevent the drastic reaction The
above surface treatment procedure
Step 05
surface cleaned fabric with 15
wt% PA at 40°C for 2 h washing
with distilled water and dried for
2 days at room temperature.
Kevlar Treatment

9. Treatment 01 Treatment 02
Alkaline treatment
Sulpho ferric etching
Treatment 03
Forest product laboratory
Treatment 04
Chromic anodizing
Treatment 05
Phosphoric anodizing
Aluminium Treatment

10. Alkaline treatment
 120gm NAOH+880ml h20
 4M solution
 4min,room temp
Sulpho ferric etching:
127gm feso4 + 185ml +
h2so4 + 688ml h20
10min, 65°C
Forest product laboratory:
50gm Na2Cr2o7 + 330
ml conc h2so4+h20
 20mins,room temp
Aluminium Treatment

11. Chromic anodizing:
• 20mlcro3 30mlh2so4 h20
• 50min, 15 v, room temp
.
Phosphoric anodizing:
20ml H3po4+ 3ml hno3 + h20
30 min, 15 v, room temp
Cathode: steel
Anode: specimen
Power: 15v dc

12. EFFECT OF ALUMINIUM TREATMENT

13. DCB
ASTM D5528-01
the high load with less
delamination will accept
as a good or the best
treatment.
t3<t5<t4<t1<t2<t0
t3,t5,t4 has good fracture
toughness and high
resistance to delaminate.
but t3 has higher material
loss. t4 has poor statics
on environment because
of chrome, so the best
treatment is concluded as
t5.

15. Why flexural?
To find best hybrid
combination by both
compressive and tensile

16. ASTM D790-03
1. σf = ( 3PL/2bd2 )[ 1 + 6(D/L)2- 4(d/L)(D/L) ]
2. Ef=6Dd/L2
3. E=Lm3/4bd3
where:
• σf = stress in the outer fibers at midpoint, Mpa
• Ef = strain in the outer surface, mm/mm,
• E = modulus of elasticity in bending, MPa ,
• P = load at a given point on the load-deflection curve, N
• L = support span, mm
• b = width of beam tested, mm
• d = depth of beam tested, mm
• D = deflection of the centerline of the specimen at the
middle of the support span, mm.
• m = slope of the tangent to the initial straight-line portion
of the load-deflection curve, N/mm of deflection.

19. Why leaf
spring?
GARALL has higher
stain energy and
elastic property will
allow to store more
energy.

20. For steal
For GARALL
N=9528 CYCLE
N=250000
CYCLE
FOR 5000N

21. MAX STRESS
(N/mm.sq)
MIN STRESS
(N/mm.sq)
DEFLECTION
(mm)
MAX
STAIN
ENERGY
MIN STAIN
ENERGY
STEEL 1000000 95628 20 100000 6528
GARALL 3000000 100000 45 250000 99000
ANSYS DATA
FATIGUE LIFE FACTOR OF SAFETY
STEEL 9528 5
GARALL 250000 17

22. Making a
conclusion
This research work provides
comparative analysis between conventional
steel leaf spring and hybrid GARALL
composite leaf spring.
At various loading conditions,
hybrid composite leaf spring is found to have
lesser stresses and negligible higher
deflection as compared to conventional steel
leaf spring.
Hybrid composite has higher
elastic strain energy storage capacity than
steel composite because it has lower young’s
modulus and lower density as compared to
both. Hence hybrid composite leaf spring can
absorb more energy which leads to good
comfortable riding.
Weight can be reduced by
81.5% if steel leaf spring is replaced by hybrid
GARALL composite leaf spring. Weight
reduction reduces the fuel consumption of
the vehicle.

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