LAB MANUAL
AIM
Apparatus
Schematic Diagram
Theory
Precautions
Conclusion
Procedure
Observation and calculation
APPARATUS:
Apparatus of Vacuum Bagging system consists of three major parts
1)Plumbing system
Plumbing system is made up of Vacuum pump, Vacuum Hose, Vacuum Control Valve ,Vacuum Throttle Valve, Resin trap and vacuum port interconnected by using metallic piping and vacuum fittings with Vacuum Gauge attached close to vacuum lines in order to monitor the vacuum bagging system pressure
2)Fabrics, Mold And Reinforcements
a)Release fabric
b)Perforated Film
c)Breather material
d)Mastic Sealant
e) Vacuum Bagging film
f)Fiber Glass reinforcement
3) Chemicals
Gel coat
Accelerator
Resin MATRIX
Catalyst
Releasing Agent
SCHEMATIC DIAGRAM
THEORY:
COMPOSITE
Composite material consists of at least two materials which are combined to improve combined mechanical properties that would be different to properties if materials were used as the single entity. Mainly composite materials consist of Resin Matrix and a reinforcement .added to improve the strength and stiffness of matrix, While the reinforcement is usually in fiber forms
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Composite are divided into three main types
1)Polymers matrix composites also known as FRP or fiber reinforced composite panels
2)Ceramic matrix composites
3)Metal matrix composites
VACUUM BAGGING METHOD
Vacuum Bagging System is a process which uses a two side mould to produce the Fiber reinforced composite panels. Lower side mold is rigid mainly made up of Wood while vacuum bag forms the upper to complete the mold. After completing the mold set vacuum pressure is applied on the system for improving consolidation of the composite and removing air bubbles of the Cured laminate of Fiberglass reinforced plastic. Process is mostly performed on ambient temperatures depending on the resin system used with the vacuum pressure acting on the system. Vacuum Pump or air compressor is used to extract air bubbles from the Vacuum bagging system.
PHASES DURING THE CURING OF POLYESTER RESIN:
Gel Time: Time required between the addition of curing agent and giving time for setting the resin to become a soft gel. On this stage liquid resin has lost its ability to flow viscous
Hardening Time: It’s the time when resin is hard enough and can be easily removed from the mould
Maturing Time: The time required for composite laminate to acquire its desired hardness and stability, This time can vary from few hours to weeks and it is solely dependent on Resin Matrix and the curing system used.
RULES OF MIXTURES:
1. Calculating fibre volume
2. CALCULATING THE DENSITY OF FIBER-REINFORCED COMPOSITE
3. CALCULATING UNIDIRECTIONAL PLY-Longitudinal tensile modulus
4. CALCULATING Unidirectional Ply-transverse tensile modulus
5. CALCULATING COEFFICIENT OF Longitudinal
THERMAL EXPANSION PRECAUTIONS
6. CALCULATING COEFFICIANT OF Transverse THERMAL EXPANSION
7. CALCULATING POISSON RATIO
.6.7 can be calculated
The Poisson’s ratio of an orthotropic material is different in each direction (x, y and z).
However, the symmetry of the stress and strain tensors implies that not all the six Poisson’s ratios in the equation are independent. There are only nine independent material properties; three elastic moduli, three shear moduli, and three Poisson’s ratios. The remaining three Poisson’s ratios can be obtained from the relations
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From the above relations we can see that if Ex > Ey then νxy > νyx. The larger Poisson’s ratio (in this case νxy) is called the major Poisson’s ratio while the smaller one (in this case νyx) is called the minor Poisson’s ratio. We can find similar relations between the other Poisson’s ratios.
PRECAUTIONS
1)Adequate ventilation should be there in the lab
2)Wear protective clothing
3)Avoid bare hand contact with chemicals and fiber reinforcements
4)Keep chemicals away from flame in order to avoid fire explosion
5)Avoid empty containers
6)Never use solvents that can damage the Vacuum pump
7)Make sure that Switches and electric cords are defect free
