In this paper, a tunable metamaterial consisting of periodic layers of steel, polyurea and piezoelectric ceramic transducer
(PZT) was presented. The PZT layer in this structure was connected to an inductor L. Transfer matrix method was used
to calculate the band structure of the sample. It was observed that an extremely narrow stop band was induced by the
PZT layer with inductor L. This narrow stop band was attributed to the resonance circuit constituted by the piezoelectric
layer, for the piezoelectric layer with electrodes could be seen as a capacitor. Further, homogenization was used to
calculate the effective elastic constants of the sample. Results showed that the effective parameters of this structure
behaved negative in the narrow stop band. The location of the narrow stop band was in the charge of inductor L, which
could be used to design acoustic filters or noise insulators by changing the parameters of structure.
Polyurea is a type of elastomer with excellent properties and a myriad of applications. Especially, the application in increasing the survivability of structures and buildings under impact loading is more attractive. Recently, modifying the properties of polyurea by mixing micro and nano particles into polyurea is becoming a new research hotspot. However, systematic study of the effect of particles size on the properties of polyurea-based composites has not been reported. Hence, in our present work, glass beads with diameters in the range from 3μm to 250μm were selected and composites with 20% volume fraction of glass beads were prepared. Microstructure of the composites was investigated by Scanning Electron Microscopy (SEM). Dynamic mechanical analysis was conducted using a TA Instruments DMA 2980 over the temperature range from -80°C to 50°C at various frequencies. The storage and loss moduli master curves for these composites were obtained through application of the time-temperature superposition (TTS). Ultrasonic properties were determined by a personal computer (PC) based ultrasonic system at room temperatures. Velocity and attenuation of longitudinal ultrasonic wave were measured. Consequently, complex longitudinal modulus was computed from these measurements. Evaluation of the effect of particle size on the properties of the composites mentioned above was presented.
Due to its excellent thermo-mechanical properties, polyurea is attracting more and more attention in blast-mitigating
applications. In order to enhance its capability of blast-induced stress-wave management, we seek to develop polyurea-based
composites in this work. Fly ash which consists of hollow particles with porous shell and low apparent density
was chosen as filler and a series of fly ash/polyurea composites with various fly ash volume fractions were fabricated.
The dynamic mechanical behavior of the composites was determined by a personal computer (PC) based ultrasonic
system in the 0.5-2MHz frequency range between -60°C to 30°C temperatures. Velocity and attenuation of both
longitudinal and shear ultrasonic waves were measured. The complex longitudinal and shear moduli were then computed
from these measurements. Combining these results provided an estimate of the complex bulk and Young’s moduli of the
fly ash/polyurea composites at high frequencies. These results will be presented and compared with those of pure
polyurea elastomer.
Fly ash, which consists of hollow particles with porous shells, was introduced into polyurea elastomer. A one-step
method was chosen to fabricate pure polyurea and the polyurea matrix for the composites based on Isonate® 2143L
(diisocyanate) and Versalink® P-1000 (diamine). Scanning electron microscopy was used to observe the fracture
surfaces of the composites. Particle size and volume fraction were varied to study their effects on the tensile properties
of the composites. The tensile properties of the pure polyurea and fly ash/polyurea (FA/PU) composites were tested
using an Instron load frame with a 1 kN Interface model 1500ASK-200 load cell. Results showed that fly ash particles
were distributed homogeneously in the polyurea matrix, and all of the composites displayed rubber-like tensile behavior
similar to that of pure polyurea. The tensile strength of the composites was influenced by both the fly ash size and the
volume fraction. Compared to the largest particle size or the highest volume fraction, an increase in tensile strength was
achieved by reducing particle size and/or volume fraction. The strain at break of the composites also increased by using
fine particles. In addition, the composites filled with 20% fly ash became softer. These samples showed lower plateau
strength and larger strain at break than the other composites.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.