Experimental Study on the Bending Behavior of 3D Woven Glass Fiber Sandwich Composite Panels

Three-dimensional integrated woven sandwich composites (IWSCs) consist of two woven fabric faces
and an integrated hollow core. The two parallel faces are bonded using pile yarns which keep a defined
distance between the top and bottom. In order to characterize the mechanical properties, three-point
bending test was performed on the IWSC sandwich composites. The results showed that by increasing
the thickness of the composite and therefore increasing the moment of inertia, the flexural strength of
the specimens increases. The average amount of bending force increase by increasing the thickness for
different samples is equal to 80% to 120%. Also, by increasing the pile density, the flexural strength
in hybrid and non-hybrid specimens increases. Therefore, the maximum flexural load is obtained from
the composites with the highest thickness and pile density. On the other hand, due to the different
arrangement of piles in the warp and weft directions, IWSC panels show different behavior in these two
directions. The values of flexural strength in the direction of the warp are higher than the direction of the
weft due to the higher density of pile yarns and therefore the higher shear strength of the structure in this
direction. In different composites, this difference is 75% to 90%. The fracture properties of the composite
under bending load show that due to the high strength and modulus of the face-sheets compared to the
core section, the piles are more deformed and damaged and the face-sheets are not noticeably damaged.
Also, the damage to the top face sheets of samples tested in the weft direction is greater than that of warp
direction.