Microwave Absorbing Properties of Lightweight Nanocomposite/Honeycomb Sandwich Structures

Author(s):  
A. A. Khurram ◽  
Sobia A. Rakha ◽  
Naveed Ali ◽  
M. T. Asim ◽  
Zhang Guorui ◽  
...  

Thin glass-fiber/epoxy-composite sheets filled with multiwalled carbon nanotubes (MWCNTs) are manufactured to make lightweight honeycomb sandwich microwave absorbers. A multilayered sandwich structure of thin nanocomposite sheets and honeycomb spacers have been also proposed and developed to work in a wide frequency range. The nanocomposite sheets are prepared from 0.5, 1.0, 1.5, 2.0, and 2.5 wt. % of MWCNTs. A commercially available simulation software computer simulation technology (CST) microwave studio was used for the designing and development of radar absorbing structure (RAS) composed of MWCNTs/glass-fiber/epoxy-composite sheets and honeycomb cores. The measurements of return loss (RL) from sandwich structures with 5 mm and 20 mm honeycomb cores in the Ku band (11–17 GHz) show that maximum RL is achieved at 11 GHz and 16 GHz, respectively. The stacking of three nanocomposite sheets and three 5 mm-thick honeycomb spacers produced a wide band microwave absorber with −10 dB RL over 9 GHz bandwidth.

2016 ◽  
Vol 58 (4) ◽  
pp. 333-336 ◽  
Author(s):  
Hawa Ahmad ◽  
Mohd. Shukry Abdul Majid ◽  
Mohd. Afendi Rojan ◽  
Fauziah Mat ◽  
Yakubu Dan-Mallam

Author(s):  
H Geramizadeh ◽  
S Dariushi ◽  
S Jedari Salami

The current study focuses on designing the optimal three-dimensional printed sandwich structures. The main goal is to improve the energy absorption capacity of the out-of-plane honeycomb sandwich beam. The novel Beta VI and Alpha VI were designed in order to achieve this aim. In the Beta VI, the connecting curves (splines) were used instead of the four diagonal walls, while the two vertical walls remained unchanged. The Alpha VI is a step forward on the Beta VI, which was promoted by filleting all angles among the vertical walls, created arcs, and face sheets. The two offered sandwich structures have not hitherto been provided in the literature. All models were designed and simulated by the CATIA and ABAQUS, respectively. The three-dimensional printer fabricated the samples by fused deposition modeling technique. The material properties were determined under tensile, compression, and three-point bending tests. The results are carried out by two methods based on experimental tests and finite element analyses that confirmed each other. The achievements provide novel insights into the determination of the adequate number of unit cells and demonstrate the energy absorption capacity of the Beta VI and Alpha VI are 23.7% and 53.9%, respectively, higher than the out-of-plane honeycomb sandwich structures.


Author(s):  
Maddigatla Vinod Kumar Reddy ◽  
R.V.S. Lakshmi ◽  
Y. Pragathi ◽  
P. Devaraj ◽  
N. Naresh

Author(s):  
Sushila Chowdhary ◽  
Mesfin Kebede Kassa ◽  
Yitbarek Gashaw Tadesse ◽  
Ananda Babu Arumugam ◽  
Rajeshkumar Selvaraj

In this study, the instability regions of a honeycomb sandwich plate are investigated for different end conditions under periodic in-plane loading. The core layer of the sandwich plate is made of carbon nanotube (CNT)/glass fiber-reinforced honeycomb and the face layers of CNT/glass fiber- reinforced laminated composite. The governing equations are derived using classical laminated plate theory (CLPT) and solved numerically by using finite element formulation. The effectiveness of the developed finite element formulation is demonstrated by comparing the results in terms of natural frequencies with those available in the literature. The effects of CNT wt.% on the core material, CNT wt.% on the skin material, ply orientation and various end conditions on the variation of natural frequencies, loss factors and instability regions are studied. Finally, some inferences for the effects of CNT reinforcement on the honeycomb sandwich plate subjected to the periodic in-plane loads are discussed.


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