Study on the Effect of Fabric Shear Deformation on the Bending Properties of Helmet Shell Composites
Pilot's helmet wearing and removing need shell in the elastic range of a certain deformation.Through the process of designing a reasonable adjustment of the shell stiffness the comfort of the helmet can be improved.In this paper,the effect of shear deformation of multilayered biaxial weft knitted fabrics on the flexural properties of composite sheets reinforced by them is investigated.The deformation of the fabric at different positions of the helmet was investigated using the zoning method.Mechanical properties and damage morphology of composites by universal testing machine and ultra-depth three-dimensional microscope was characterized.The results show that the bending stiffness of the composites is greatly affected by the shear deformation,which shows a tendency of first increasing,then decreasing and then increasing with the increase of the shear angle.The bending strength of composites is less affected by shear deformation and is minimized when the shear angle is between 20° and 30°.This paper confirms that the stiffness of composites can be effectively adjusted by using the shear deformation of fabrics,which can provide a reference for the optimized design of helmet shell stiffness.
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