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Description
Carbon nanotubes (CNTs) have emerged as compelling materials for enhancing both electrical and mechanical properties of aerospace structures. Buckypaper (BP), a porous
membrane consisting of a highly cross-linked network of CNTs, can be effectively
integrated with carbon fiber reinforced polymer (CFRP) composites to simultaneously
enhance their electromagnetic interference (EMI) shielding effectiveness (SE) and
mechanical properties. In existing literature, CNT based nanocomposites are shown to
improve the flexural strength and stiffness of CFRP laminates. However, a limited amount
of research has been reported in predicting the EMI SE of hybrid BP embedded CFRP
composites.
To characterize the EMI shielding response of hybrid BP/CFRP laminates, a novel
modeling approach based on equivalent electrical circuits is employed to estimate the
electrical conductivity of unidirectional CFRP plies. This approach uses Monte Carlo
simulations and accounts for the effects of quantum tunneling at the fiber-fiber contact
region. This study specifically examines a signal frequency range of 50 MHz to 12 GHz,
corresponding to the very high to X band spectrum. The results indicate that at a frequency
of 12 GHz, the longitudinal conductivity decreases to around ~3,300 S/m from an initial
DC value of 40,000 S/m, while the transverse conductivity concurrently increases from
negligible to approximately ~12.67 S/m. These results are then integrated into Ansys High
Frequency Structure Simulator (HFSS) to predict EMI SE by simulating the propagation
of electromagnetic waves through a semi-infinite composite shield representative volume
element. The numerical simulations illustrate that incorporating BP allows for significant
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improvements in SE of hybrid BP/CFRP composites. At 12 GHz signal frequency, for
example, the incorporation of a single BP interleave enhances the SE of a [90,0] laminate
by up to ~64%, while the incorporation of two BP interleaves in a [90,0,+45,-45,0,90]s
balanced symmetric laminate enhances its SE by ~20% . This enhancement is due to the
high conductivity of BP at high frequencies.
Additionally, to evaluate the flexural property enhancements due to BP, experimental
three-point bend tests were conducted on different configurations of hybrid BP/CFRP
laminates, and their strength and stiffness were compared with the non-BP samples.
Micrographs of failed samples are acquired using an optical microscope, which provides
insights into their underlying damage mechanisms. Fractography analysis confirms the role
of BP in preventing through-thickness crack propagation, attributed to the excellent crack
retardation properties of CNTs.
ContributorsTripathi, Kartik (Author) / Chattopadhyay, Aditi (Thesis advisor) / Henry, Todd C. (Committee member) / Nian, Qiong (Committee member) / Arizona State University (Publisher)
Created2024