Investigating the dynamic mechanical behaviors of polyurea through experimentation and modeling

Wang, Hao; Deng, Xun; Wu, Haijun; Pi, Aiguo; Li, Jinzhu; Huang, Fenglei

doi:10.1016/j.dt.2019.04.016

Cited by 63 publications

(22 citation statements)

References 14 publications

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“…The mechanical properties of OCA material will directly affect the design process and the evaluation of reliability. Therefore, it is essential to conduct a comprehensive mechanical behavior analysis and establish a reasonable material constitutive model before conducting design and rapid reliability assessments [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Behavior and Constitutive Model Characterization of Optically Clear Adhesive in Flexible Devices

et al. 2022

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Optically clear adhesive (OCA) has been widely used in flexible devices, where wavy stripes that cause troublesome long-term reliability problems often occur. The complex mechanical behavior of OCA should be studied, as it is related to the aforementioned problems. Therefore, it is necessary to establish reasonable mechanical constitutive models for deformation and stress control. In this work, hyperelastic and viscoelastic mechanical tests were carried out systematically and relative constitutive models of OCA material were established. We found that temperature has a great influence on OCA’s mechanical properties. The stress and modulus both decreased rapidly as the temperature increased. In the static viscoelasticity test, the initial stress at 85 °C was only 12.6 kPa, 57.4% lower than the initial stress at 30 °C. However, in the dynamic test, the storage modulus monotonically decreased from 1666.3 MPa to 0.6628 MPa as the temperature rose, and the decline rate reached the maximum near the glass transition temperature (Tg = 0 °C). The test data and constitutive models can be used as design references in the manufacturing process, as well as for product reliability evaluation.

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Section: Introductionmentioning

confidence: 99%

Mechanical Behavior and Constitutive Model Characterization of Optically Clear Adhesive in Flexible Devices

et al. 2022

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“…The latter loads the polyurea sample and generates a hoop stress (𝜎 r ) that can be estimated by assuming the pressure cavity between the polyurea sample and the glass substrate is a thin wall spherical pressure vessel (e.g., 𝜎 𝜃 = Pr 2t , where, P is the build-up pressure acting on polyurea, r is the radius of curvature of the bulge area (measured optically and taken to be 6.2 mm), and t is the thickness of the polyurea film. The resulting hoop stress developed in the polyurea film is estimated to be 32.80 MPa, pointing to a flow strength of 30 MPa at strain rate of 10 3 s −1 based on the work of Wang et al [62] The excessive plastic bulging deformation discussed above was associated with high mechanical work done on the material, resulting in a localized shear deformation due to the conversion of the mechanical work to heat. [69,70] The localized shear deformation is associated with the high compressive stress wave due to shock loading.…”

Section: Ductile Failure Of Shock-loaded Polyureamentioning

confidence: 98%

“…Wang et al reported the flow stress of polyurea to range between 10 MPa and 43 MPa as the strain rate changes from 10 −3 to 10 4 s −1 , respectively. [62] The upper bound of the flow stress leads to partial or total spallation without leaving evidence of plastic deformation. In the optical micrographs shown in Figure 8 (note that polyurea films were removed from the test structure and were placed on a mounting substrate for optical microscopy), the plastic bulging indicates another mechanism must have been at play given the forecasted pressure build-up due to the generation of the shock wave based on the interaction of the laser illumination and the localized energy sacrificial layer.…”

Section: Ductile Failure Of Shock-loaded Polyureamentioning

confidence: 99%

Spectro‐Microscopic Characterization of Elastomers Subjected to Laser‐Induced Shock Waves

Huynh

Gámez

Youssef

2021

Macro Materials & Eng

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The core of this research is separated into three domains, the ultrahigh strain rate response of elastomeric polymers, laser-induced shock waves , and terahertz time-domain spectroscopy (THz-TDS). Elastomers, e.g., polyurea, constitute an advance class of materials suitable for many applications, specifically in high impact loading scenarios, thus, a laser-induced shock wave (LSW) experimental technique is used to investigate the mechanical response of shock-loaded polyurea. LSW can submit samples to a strain rate exceeding 10 6 s −1 at low strains, enabling determination of material intrinsic failure modes. The large deformation induced during shock loading may alter the macromolecule structure, which can only be detected spectroscopically. Therefore, this research incorporated terahertz bulk spectroscopy to detect and report molecular conformational changes. Microscopy techniques were also used to elucidate changes in the microscale properties, morphology, and topography. The interpretation of the results explicated brittle failure in terms of partial and total spallation and, remarkably, ductile failure leading to plastic deformation, including plastic bulging and adiabatic shearing, not previously associated with LSW technique. Furthermore, spectral changes found in the terahertz regime substantiated the validity of terahertz spectroscopy in elucidating the underlying mechanism associated with the impact mitigating properties of dynamically loaded polyurea.

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“…As provided by the supplier, the composite material had a tensile strength of 15.4 MPa, breaking elongation ratio of 200%, and tear resistance of 105 N/m. The mechanical properties of the composite material are summarized in Table 3 [21].…”

Section: Materials Parametersmentioning

confidence: 99%

Experimental and Numerical Study of Polymer-Retrofitted Masonry Walls under Gas Explosions

Gu¹,

Ling²,

Wang³

et al. 2019

Processes

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Unreinforced masonry walls are extensively used in the petrochemical industry and they are one of the most vulnerable components to blast loads. To investigate the failure modes and improve the blast resistances of masonry walls, four full-scale field tests were conducted using unreinforced and spray-on polyurea-reinforced masonry walls subjected to gas explosions. The results suggested that the primary damage of the unreinforced masonry wall was flexural deformation and the wall collapsed at the latter stage of gas explosion. The presence of polyurea coatings could effectively improve the anti-explosion abilities of masonry walls, prevent wall collapses, and retain the flying fragments, which would reduce the casualties and economic losses caused by petrochemical explosion accidents. The bond between the polymer and masonry wall was critical, and premature debonding resulted in a failure of the coating to exert the maximum energy absorption effect. A numerical model for masonry walls was developed in ANSYS/LS-Dyna and validated with the test data. Parametric studies were conducted to explore the influences of the polyurea-coating thickness and spray pattern on the performances of masonry walls. The polyurea-coating thickness and spray pattern affected the resistance capacities of masonry walls significantly.

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Investigating the dynamic mechanical behaviors of polyurea through experimentation and modeling

Cited by 63 publications

References 14 publications

Mechanical Behavior and Constitutive Model Characterization of Optically Clear Adhesive in Flexible Devices

Mechanical Behavior and Constitutive Model Characterization of Optically Clear Adhesive in Flexible Devices

Spectro‐Microscopic Characterization of Elastomers Subjected to Laser‐Induced Shock Waves

Experimental and Numerical Study of Polymer-Retrofitted Masonry Walls under Gas Explosions

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