Design And Wave Absorbing Performance Of Sandwich Composites With Glass Fibers/Carbon Fibers/Metamaterial Absorbers Integrated

Stealth technology can provide the function of hiding the target characteristic signals and thus reduce the probability of being detected,therefore plays a very important role in modern warfare.Wave absorbing materials occupies an important position in the field of stealth technology.In recent years,with deep research on metamaterials carried out,metamaterial absorbers gradually come into people's sight.Through accurate design and precision fabrication,metamaterial absorbers could be obtained.When it was embedded into the material structure,the final materials would show very ideal wave absorbing performance.This thesis mainly focuses on the design of glass fibers/carbon fibers sandwich composites with metamaterial absorbers integrated.The metamaterial absorbers were embedded into the sandwich composites to form the wave absorbing glass fibers/carbon fibers sandwich composites.The sandwich composites include the glass fibers/carbon fibers surface layers and the core layers,and the final glass fibers/carbon fibers composite materials would have both wave absorbing and load-bearing properties.The detailed research content and conclusions of this thesis are as follows:(1)The single-band metamaterial absorber was designed and the designed absorber exhibited negative electromagnetic parameters,showing that it owned metamaterial characteristics.The real absorber was prepared by the printed circuit board(PCB)technology,and the microwave absorption was tested.The results showed that the absorptivity of the designed metamaterial absorber was 99.99% at the frequency of 10.30 GHz.By testing the absorptivity of metamaterial absorber under different electromagnetic wave incident angles,it was found that when the incident angle increased from 0 ° to 60 ° with the step length of 15°,the metamaterial absorber still showed relatively good absorption performance.(2)Three types of glass fibers/carbon fibers wave absorbing sandwich composites with different thickness were designed(According to the thickness ascending sequence,they were marked as D1,D2,D3 respectively).When the metamaterial absorbers were embedded into the sandwich composites,the detailed structure design from the upper to the bottom was glass fiber/epoxy composite,PMI foam,metamaterial absorber,PMI foam and carbon fiber/epoxy composite;and herein,PMI foam and metamaterial absorber were designed as the core layer.After the simulation optimization and real composites fabrication,the wave absorbing performances were tested.The results showed that the three types of composites had absorptivity of 99.90%,99.50%,and 98.90% respectively at the frequency of 10.30 GHz.The designed glass fibers/carbon fibers sandwich composites still exhibited adequate absorptivity value when the incident angles changed.(3)The mechanical properties tests including tensile,bending,compression and impact were conducted for the above three glass fibers/carbon fibers wave absorbing sandwich composites,and the corresponding data were analyzed.The fractured cross sections after bending and impact tests were observed by SEM.The mechanical testing results showed that for the strengths obtained from four types of mechanical properties tests,D1 had overall higher value than D2 and D3.The tensile and compression moduli from D3 had significant lower value when compared with D1 and D2.SEM results showed that the interlaminar bonding of D1 was good,and the fractured cross sections after impact test of three types of composites were flat.(4)To meet the requirement of multiple and broad working frequency bands,the dualband and broadband wave absorbing glass fibers/carbon fibers sandwich composites were designed.And the wave absorbing performance tests and the bending tests as well as afterfracture SEM observation of the real composites were conducted.The results showed that the dual-band sandwich composite had absorptivity of 94.13% and 99.99% at 8.65 GHz and 10.30 GHz and the broadband sandwich composite had absorptivity of 90.02%?99.91% in 8.25GHz? 11.61 GHz frequency range with the relative bandwidth of 33.84%.The bending strength of broadband sandwich composite was 111.83% higher than the dual-band composite.SEM results showed that the two types composites had overall good interlaminar bonding with small range of delamination observed.