introduction to composites

2. Fig: Tacoma Narrows Bridge
(July 1940 to oct,1940)
Fig: Missipi river bridge collapse in 2008
(nov,1967 to sep,2008)
Spectacular accidents have motivated the community to improve safety

3. Evolution of materials
Reference : American iron
and steel institute/U.S
department of energy
Reference : dallara altairamerica HTC , maya2012

4.  The advantages of composite structures are that they
can be designed to suit the requirements of a specific
application or to enhance some properties of the
structure such as
 Strength and stiffness in desired directions of
dominant loads.
 corrosion resistance.
 desired temperature-dependent behavior . etc

5.  Composite materials are used in almost all aspects of
the industrial and commercial fields in aircraft, ships,
common vehicles, medical application , construction
etc
 Their most attractive properties are the high strength-
to-weight ratio and high stiffness-to weight ratio

6.  These new materials also have some problems such as
fiber breakage, matrix cracking, debonding, and
delamination.
 This damage can cause degradation of strength and
overall stiffness for a laminate structure.
 The presence of delamination can also significantly
reduce the buckling load and compressive strength of
the composite laminate

7. One of the main reason for the failure of the equipment
made by composite material is due to fatigue .
So S.H.M. is necessary to predicts the life and type of failure
in the specimen.

8.  Structural vibration and acoustics
 Electro mechanical impedance
 Acoustic emission
 Ultrasonic testing
Main difficulties to use this techniques are
 frequency range and resolution is limited .
 Capture signals from other environmental noise
while the structure is in operation.
 Required completely damp zone.
 Testing equipment need to be in contact with the
target.

9.  To overcome these drawbacks, vibration based
techniques for a structural health monitoring (SHM)
tool use to identify and assess defects.
 The key purpose of SHM is to ensure rapid assessment
of the health condition of a structure in terms of
reliability and safety.
 Advantage of vibration base technique
 not having contact with the specimen.
 remote measurements.
 ample frequency response.
 high sensibility.
 Portability.

11. F.E.A Experimental values
Healthy specimen Damage Specimen
(Rectangular notch )
Healthy specimen Damage Specimen
(Rectangular notch )
33.267 33.158 33.750 33.750
231.07 228.36 233.75 230.46
593.46 584.76 595.4 583.75
1144.4 1123.4 1146.4 1126.25

12.  Its non-destructive testing
 Its able to predict the life of the structure.
 find the defects present in the structure.
 helps in pre-indicate the catastrophically
failure.

14.  Specimen specification
Length = 0.220m
Width = 0.50mm
Damage -Rectangular notch
= 0.089mto 0.101m(12mm)
Density = 2700kg/m3
Fig: damage by Fractal
dimension technique
Fig: damage by gapped
smoothening technique