Flexural behavior of composites reinforced with innovative 3D integrated weft-knitted spacer fabrics

Abstract

This paper undertakes to study the flexural behavior of 3D integrated weft-knitted spacer composites, under three-point bending. The integrated-knitted spacer fabrics were produced with various cross-sectional shapes on a computerized flat-knitting machine utilizing electrical grade glass (E-glass) fibers. The sandwich composites were manufactured by vacuum-assisted resin transfer molding using unsaturated polyester resin. Continuing the process, hand lay-up method was used to reinforce the face sheets of fabricated sandwich structure with glass woven fabrics. Bending performance of the produced composites was compared with polyurethane foam core sandwich composites. The results revealed that the cross-sectional shape has significant effect on the bending performance of the 3D integrated weft-knitted spacer composites. Also, the spacer reinforced composite with V-shape cross-section has the highest bending stiffness than composites with U-shape cross-section as well as polyurethane foam core sandwich composite. The failure modes of 3D integrated weft-knitted spacer composites include: core shear failure, compression failure of upper face sheet and tensile failure of lower face sheet.

The effect of core geometry on flexural stiffness and transverse shear rigidity of weight‐wise identical corrugated core sandwich panels reinforced with 3D flat spacer knitted fabric

“…The flexural load‐carrying capacity of the triangular core sandwich panel at a given deflection level is 9× and 4× higher than that of the rectangular and hat‐type structures, respectively. This result is in line with Hassanzadeh et al [ 13 ] and Azadian et al [ 14 ] findings. The reduction in the core wall to skin angle has resulted in higher load carrying capacity of the core wall during bending.…”

“…It was stated that the transverse shear rigidity in the direction of corrugation for the triangular structure is considerably higher than that for the hat‐type structure. Hassanzadeh et al [ 13 ] and Azadian et al [ 14 ] experimentally compared transverse bending of the integrated corrugated core sandwich panels of different weights. It was stated that the triangular structure has greater load‐carrying capacity than the rectangular structure in the direction of corrugation.…”

A review on recent advances in sandwich structures based on polyurethane foam cores

“…Other research on 3D woven fabric sandwich specimens from past years focused on the flexural behavior, type of reinforcing material and fatigue response. A detailed study related to flexural performance of 3D woven sandwich composites made of glass fabrics was conducted by Azadian et al Sandwich specimens were prepared by knitting the fabrics in different shapes such as U‐shape and V‐shape specimens. PUF was used as a filler to make hybrid sandwich composites, and specimens with and without PUF were subjected to three‐point bending loads.…”

Free vibration analysis of integrated and non-integrated corrugated core sandwich panels reinforced with weft-knitted fabrics

“…Corrugated cores have excellent resistance to shocks and can serve as anti-vibration materials or sound insulations [2]. However, due to the small contact surface area between the core and the skin, the core-to-skin bond in corrugated sandwich panels in general and in particular in composite materials can be disadvantageous [5,6].…”

“…The structural parameters of weft-knitted fabrics such as course per centimeter (CPC) or the yarn count were varied in such a manner that the weight per unit area of reinforcement fabric remained unchanged. Previous researches have illustrated that 3-D weft-knitted fabric is a desirable reinforcing element for integrated sandwich panels, and additionally, the VARTM is a proper method for the production of these types of composites [5,[22][23][24][25].…”