Design of a Composite Drive Shaft and its Coupling for Automotive Application, M.R. Khoshravan / 826‐834
828 Vol. 10, December 2012
strength and a 90º angle is the best for buckling
strength [10]. The main goal design is to achieve
the minimum weight while adjusting the variables
to meet a sufficient margin of safety, which is
translated in a critical speed (natural frequency)
higher than the operating speed (above 9200 rpm),
a critical torque higher than the ultimate
transmitted torque and a nominal stress (the
maximum at fiber direction) less than the allowable
stress after applying any of the failure criteria like
the maximum stress criteria (for example Tsai-Hill
criteria). Due to the physical geometry (larger
radius) of the drive shafts used in the mentioned
applications including automotive applications, the
shear strength, which specifies the load carrying
capacity,it is of minor design importance since the
failure mode is dominated by buckling therefore
the main design factors are the bending natural
frequency and the torsional buckling strength,
which are functions of the longitudinal and hoop
bending stiffness, respectively [10].
The material properties of the drive shaft were
analyzed with classical lamination theory (CLT). The
variable of the laminate thickness has a big effect
on the buckling strength and slight effect on bending
natural frequency. From the properties of the
composite materials, at given fiber angles, the
reduced stiffness matrix can be constructed. The
expressions of the reduced stiffness coefficients Qij
in terms of engineering constants are as follows [3]: