The feasibility of replacing currently widely used sandwich construction with
helically stiffened construction for a Formula racing car structural shell is studied.
The torsional deformation behavior of circular and square cross-section shells is
analyzed as an approximation to the real car structure. Shells with different
sandwich and helically stiffened configurations are analyzed with finite elements.
For closed square and circular cross-section shells, the highest torsional stiffness is
obtained with helical stiffening. For circular cross-section shells with the cockpit
cutout and reinforcements usually present in real racing car structural shells, ±4S'
helically stiffened shells are 200% stiffer in torsion than sandwich shells. For
square cross-section shells, the torsional stiffness improvernent obtained with the
helical stiffening is only 27%. The cross-sectional shape of the shell, cockpit
opening, and different type of reinforcements (present in a real car structure)
affects the selection of the best stiffening for torsional stiffness. The role of the
terms of the stiffness matrix of the helically stiffened configuration in the torsional
behavior of the shells is studied. The 0/90 waffle stiffening is more efficient than
the helical stiffening for the square cross-section shells with the cutout and
reinforcements. In the case of circular cross-section shells, the 0/90 waffle
stiffening yields approximately the same results than the helical stiffening. The
skin-stiffener configuration for maximun torsional stiffness depends on the crosssectional
shape of the shell. The advantages of the ±45° helical stiffening over the
sandwich construction depend on the cross-sectional shape of the shell and on the
way the cutout region is reinforced.
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