Meso-scale computational investigation of polyurea microstructure and its role in shockwave attenuation/dispersion

Mica Grujicic; Jennifer Snipes; S. Ramaswami; Mica Grujicic; Jennifer Snipes; S. Ramaswami

doi:10.3934/matersci.2015.3.163

AIMS Materials Science

2015, Volume 2, Issue 3: 163-188. doi: 10.3934/matersci.2015.3.163

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Research article

Meso-scale computational investigation of polyurea microstructure and its role in shockwave attenuation/dispersion

Department of Mechanical Engineering, Clemson University, Clemson SC 29634, USA

Received: 12 March 2015 Accepted: 18 June 2015 Published: 01 July 2015

In a number of recently published studies, it was demonstrated that polyurea possesses a high shockwave-mitigation capacity, i.e. an ability to attenuate and disperse shocks. Polyurea is a segmented thermoplastic elastomer which possesses a meso-scale segregated microstructure consisting of (high glass-transition temperature, T_g) hydrogen-bonded discrete hard domains and a (low T_g) contiguous soft matrix. Details of the polyurea microstructure (such as the extent of meso-segregation, morphology and the degree of short-range order and crystallinity within the hard domains) are all sensitive functions of the polyurea chemistry and its synthesis route. It has been widely accepted that the shockwave-mitigation capacity of polyurea is closely related to its meso-phase microstructure. However, it is not presently clear what microstructure-dependent phenomena and processes are responsible for the superior shockwave-mitigation capacity of this material. To help identify these phenomena and processes, meso-scale coarse-grained simulations of the formation of meso-segregated microstructure and its interaction with the shockwave is analyzed in the present work. It is found that shockwave-induced hard-domain densification makes an important contribution to the superior shockwave-mitigation capacity of polyurea, and that the extent of densification is a sensitive function of the polyurea soft-segment molecular weight. Specifically, the ability of release waves to capture and neutralize shockwaves has been found to depend strongly on the extent of shockwave-induced hard-domain densification.
- Polyurea,
- Meso-scale,
- Coarse-grained simulations,
- Shockwave attenuation,
- shockwave dispersion
Citation: Mica Grujicic, Jennifer Snipes, S. Ramaswami. Meso-scale computational investigation of polyurea microstructure and its role in shockwave attenuation/dispersion[J]. AIMS Materials Science, 2015, 2(3): 163-188. doi: 10.3934/matersci.2015.3.163

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Abstract

In a number of recently published studies, it was demonstrated that polyurea possesses a high shockwave-mitigation capacity, i.e. an ability to attenuate and disperse shocks. Polyurea is a segmented thermoplastic elastomer which possesses a meso-scale segregated microstructure consisting of (high glass-transition temperature, T_g) hydrogen-bonded discrete hard domains and a (low T_g) contiguous soft matrix. Details of the polyurea microstructure (such as the extent of meso-segregation, morphology and the degree of short-range order and crystallinity within the hard domains) are all sensitive functions of the polyurea chemistry and its synthesis route. It has been widely accepted that the shockwave-mitigation capacity of polyurea is closely related to its meso-phase microstructure. However, it is not presently clear what microstructure-dependent phenomena and processes are responsible for the superior shockwave-mitigation capacity of this material. To help identify these phenomena and processes, meso-scale coarse-grained simulations of the formation of meso-segregated microstructure and its interaction with the shockwave is analyzed in the present work. It is found that shockwave-induced hard-domain densification makes an important contribution to the superior shockwave-mitigation capacity of polyurea, and that the extent of densification is a sensitive function of the polyurea soft-segment molecular weight. Specifically, the ability of release waves to capture and neutralize shockwaves has been found to depend strongly on the extent of shockwave-induced hard-domain densification.

References

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