design and optimization of a composite drive shaft for an automobile

Description of the Problem : The weight reduction of the drive shaft can have a certain role in the general weight reduction of the vehicle and is a highly desirable goal, if it can be achieved without increase in cost and decrease in quality and reliability. It is possible to achieve design of composite drive shaft with less weight to increase the first natural frequency of the shaft and to decrease the bending stresses using various stacking sequences. By doing the same, maximize the torque transmission and torsional buckling capabilities are also maximized.

Aim This work deals with the replacement of a conventional steel drive shaft with E-Glass/ Epoxy and High Strength Carbon/Epoxy

Optimum Design Using Genetic Algorithm The purpose of using Genetic Algorithm is to minimize the weight of the shaft, which is subjected to the constraints such as torque transmission, torsional buckling capacities and fundamental lateral natural frequency. The design parameters to be optimized are, Ply thickness Number of plies required Stacking sequence of Laminate

Composite material Composites consist of two or more materials or material phases that are combined to produce a material that has superior properties to those of its individual constituents. The constituents are combined at a macroscopic level and or not soluble in each other. The individual constituents retain those properties Advanced composite materials are widely used - High specific strength - High specific modulus

Purpose and functions of drive shaft Transfer torque – engine to rear wheels – push vehicle forward and reverse Smooth , uninterrupted flow of power to axles Transmit torque to the differential gear box During operation-transmit max low gear torque Rotate at very fast speeds required Operate through constantly changing angles b/w transmission, the differential, the axels Length of the drive must also be capable of changing while transmitting torque

DEMERITS IF A CONVENTIONAL DRIVE SHAFT Less- specific modulus strength damping capacity corrosion resistance Increased weight Manufactured in two pieces (increase bending natural frequency )

Merits of composite drive shafts High – specific modulus strength corrosion resistance damping capacity Decreased weight (one piece) Reduction in fuel consumption Greater torque capacity Lower fatigue life

Design of a steel drive shaft

Design specifications and requirements SNO NAME UNIT VALUE 1 Ultimate torque N-m 3500 2 Max. Speed of Shaft rpm 6500 3 Length of Shaft mm 1250

Mechanical properties of Steel (SM45C) MEHCHANICAL PROPERTIES UNITS STEEL Young’s Modulus GPa 207.0 Shear Modulus Gpa 80.0 Poisson’s Ratio --- 0.3 Density Kg/ 7600 Yield Strength MPa 370 Shear Strength

Torque Transmission capacity of the Drive Shaft

Torsional Buckling Capacity of the Drive Shaft If the value > 5.5 Long shaft Else it is short shaft CRITICAL STRESS : For long shaft For short and medium shafts

The relation between torsional buckling capacity and critical stress is given by

Lateral or Bending Vibration using Timoshenko Beam Theory

Design of a composite drive shaft

Selection of Material properties of e-glass/epoxy and hs carbon/epoxy SNO UNIT E-GLASS/EPOXY HS CARBON/EPOXY 1 Gpa 50.0 134.0 2 12.0 7.0 3 5.6 5.8 4 - 0.3 5 MPa 800.0 880.0 6 40.0 60.0 7 72.0 97.0 8 Kg/ 2000.0 1600.0

Torque Transmission Capacity of the Shaft Lateral or Bending Vibration Timoshenko Beam Theory

DESIGN OPTIMIZATION Objective Function: The objective for the optimum design of the composite drive shaft is the minimization of weight Design Variables Number of plies Thickness of the ply Stacking Sequence The limiting values

Design Constraints Torque transmission capacity of the shaft Bucking torque capacity of the shaft Lateral fundamental natural frequency The constraint equations if =0 otherwise =0 otherwise =0 otherwise C =

The constrained optimization can be converted to unconstrained optimization by modifying the objective function as

RESULTS AND CONCLUSIONS the ga results are shown PARAMETERS STEEL E-GLASS/EPOXY HS CARBON/EPOXY 90 L 1250 3.318 0.2431 0.1661 Optimum no. of layers 1 30 22 t(mm) 7.293 2.5542 Optimum stacking sequence - [46/-64/-15/-13/39/-84/-28/20/ ] [83/-18/-89/78/-20/-62/-78/71/ ] Weight(kg) 8.604 4.05 1.12 Weight saving (%) 41.077 85.9

GA RESULTS OF E-GLASS/EPOXY DRIVE SHAFT

GA RESULTS OF HS CARBON/EPOXY DRIVE SHAFT:

CONCLUSIONS The E-Glass/ Epoxy and HS Carbon/Epoxy composite drive shafts have been designed to replace the steel drive shaft of an automobile A one-piece composite drive shaft for rear wheel drive automobile has been designed optimally by using Genetic Algorithm with the objective of minimization of weight of the shaft. The weight savings of the E-Glass/ Epoxy and HS Carbon/Epoxy shafts were equal to 41.007% and 85.9% of the weight of steel shaft respectively

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