In-situ observation of damage evolution in polycarbonate subjected to hypervelocity impact

Kawai, Nobuaki; Nagano, Mikio; Hasegawa, Susumu; Satô, Eiichi

doi:10.1016/j.ijimpeng.2020.103584

Cited by 7 publications

(3 citation statements)

References 10 publications

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“…Rarefaction waves reflected from both the front- and back-faces interact to form an area of negative hydrostatic pressure resulting in void formation, analogous to elastic instability-induced cavitation phenomena in gels. , The secondary damage observed here has similarities to the results observed by Kawai et al. for the HVI damage of thick PC blocks. ,, They observed an area of plastically deformed material around the perforation and fracture occurring due to wave interactions perpendicular to the shortest target dimension during edge-on impacts.…”

Section: Results and Discussionsupporting

confidence: 83%

“…Adding polymeric materials to HVI shielding could potentially be beneficial due to their high strength-to-weight ratio. − Furthermore, the viscoelastic behavior of polymers is attributed to the strain-rate-dependent mechanical properties and allows energy dissipation. ,, The effectiveness of polymers in HVI conditions has been reported in the literature, ,,− but a fundamental understanding linking the materials’ responses to the underlying chemical structure, chain length (polymer molecular weight), chain relaxation behavior, and crystallinity is lacking. Upon impact from a projectile, the strain rate the target is subjected to is dependent of both its thickness and the projectile velocity.…”

Section: Introductionmentioning

confidence: 99%

“…Polycarbonate (PC) is a transparent glassy polymer that is used extensively in impact protection due to its tough and ductile nature. − The origin of such behavior is being thoroughly investigated and has primarily been attributed to the fast molecular relaxations involving multiple monomeric units along the polymer backbone. , PC has been studied in both HVI and ballistic regimes, including for thin films using LIPIT experiments. ,,, For thick PC samples, the plate impact loading in the ballistic regime resulted in various damage mechanisms, which were affected by the strain softening at a higher impact velocity as a result of adiabatic heating . In the hypervelocity regime, evidence of both ductile damage and brittle fracture has been observed. ,, The areas nearest the projectile perforation deformed in a ductile manner. However, internal fracture because of interactions between stress waves has been observed outside this plastic deformation zone.…”

Section: Introductionmentioning

confidence: 99%

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High Strain Rate Failure Behavior of Polycarbonate Plates due to Hypervelocity Impact

2022

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Developing a fundamental understanding of how polymers respond during hypervelocity impact (HVI), a high strain rate process, is crucial for the potential use of polymers in HVI protection systems. Here, we present the high-strain-rate impact behavior of commercially available polycarbonates with two different molecular weights, 42 and 21 kg/mol. A powder gun and a two-stage light-gas gun were used to achieve the velocities (v0) of a 4 mm projectile impacting the polycarbonate targets over the range of 400–6,500 m/s. The deformation behavior of the polymer during the impact event was captured using high-speed cameras. The impact caused a variety of responses, ranging from deflection of the projectile to complete perforation for higher v0, leading to major debris cloud formation. These debris clouds consist of both fluid- and dust-like ejecta. The fluid-like debris cloud indicates the melting of polymer caused by the conversion of kinetic energy to thermal energy and subsequent adiabatic heating. The dust-like response can likely be attributed to the brittle failure behavior of polymers, as the polymer became brittle at a high strain rate. Dynamic mechanical analysis (DMA) and dielectric thermal analysis (DETA) on the polycarbonate samples used here indicate an approximately 40 °C increase of T g with increasing frequency from 1 Hz to 106 Hz, and such an increase has likely led to brittle behavior. While the leading-edge velocity of the debris clouds and perforation diameters scale linearly with v0, we found negligible differences in the HVI response for the two molecular weights of polycarbonate tested here. This study displays the importance of v0 and thickness contributing to responses of polycarbonates undergoing HVI.

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