Polyurea-Based Composites: Ultrasonic Testing and Dynamic Mechanical Properties Modeling

Abstract

Many scientists and researchers study polyurea due to its excellent blast-mitigating properties. In this work, we have studied two polyurea composite systems with filler materials intended to improve dynamic mechanical properties. The two filler materials are milled glass and fly ash. The shape and quantity of filler significantly affect the dynamic mechanical properties of the composite. Ultrasonic tests were conducted on samples with both fillers. The volume fraction of the inclusions was varied to study the effect of filler quantity on mechanical properties. Moreover, computational models based on the methods of dilute-randomly-distributed inclusions and periodically-distributed inclusions were created to improve our understanding of polyurea-based composites and serve as tools for estimating the dynamic mechanical properties of similar composite material systems. The experimental and computational results were compared and show good agreement. The experiments and modeling have been conducted to facilitate the design of new elastomeric composites with desirable impact-and blast-mitigating properties. IntroductionThe failure of structures and materials in response to blast loadings is an active research area. Over the past 40 years, polyurea has been investigated as a potential coating material to help absorb and dissipate blast energy. Polyurea is the generic name for a block copolymer formed from a chemical reaction of diisocyanates with polyamines [1]. The reaction is generally very fast and insensitive to humidity and low temperatures [2]. This viscoelastic material is stable and incredibly tough, making it a popular material for coating applications. Additionally, researches have shown that polyurea also has an excellent blast-mitigating capability. Structures selectively coated with polyurea could potentially absorb more impact energy before failure and enhance the dynamic performance of structure [3][4][5][6].Recent researches have focused on modifying polyurea with filler materials to create composites with enhanced properties. Qiao et al. [7,8] reduced the density but increased the strength of polyurea by mixing it with fly ash. As the volume of fly ash increases, the density of the composite decreases, while the storage modulus as measured by dynamic mechanical analysis (DMA) increases. Alternatively, glass fibers can be blended with a polymer to greatly improve the strength of the polymer [9]. Tests on milled-glass-fiber-filled polyethylene terephthalate-co-isophthalate composites were conducted by Velasco et al. [10]. Their results showed a trend of increasing modulus with increasing fiber volume fraction. Increasing wear resistance is another advantage of polymer composites containing milled glass fibers [11].In this work, two kinds of composites with different inclusion shapes were studied with two objectives in mind: (1) to investigate the effect of inclusion content on dynamic mechanical properties and (2) to present the models which effectively

Constitutive modeling and experimental calibration of pressure effect for polyurea based on free volume concept

“…The test system consists of ultrasonic wave measurement setup, quasistatic confined loading setup, and temperature control chamber. The ultrasonic measurements were performed in the through-transmission mode, using a desktop computer with a Matec TB-1000 Toneburst card, two Panametrics videoscan longitudinal transducers (V103 Panametrics-NDT OLYMPUS), a 100:1 attenuator box, and a digital oscilloscope (Tektronix DPO3014) [23]. Toneburst signals of prescribed frequencies were generated from the card and split through BM-174-3 cables to the pitching transducer and the attenuator box, where the voltage was reduced by a factor of 100 to be measured on the scope.…”

Assessment of Multilayered Plates with Hyperelastic Coatings Subjected to Dynamic Loadings by Impact at Low Velocities

“…In this regard, for a better understanding of materials behavior, during the experimental tests (mechanical testing, ultrasonic testing), different types and configurations of samples and measurement tools have been tested (simple/bilayer/multilayer configurations, force or pressure transducers, videospeed cameras, scanning electron microscopy, computed tomography etc. ), in static, dynamic or impulsive regime, corroborated with numerical simulation, in order to obtain valid outcomes and results that can be extrapolated to large-scale experiments and applications [13,[20][21][22][23][24][25][26][27][28][29].…”

“…Also, in terms of test instrumentation, besides classical sensors (transducers), the potential of high-speed photography, digital image correlation methods and X-ray computed tomography (CT), the comparison between experimental data and numerical simulations [13,19,21,[26][27], has been investigated.…”