Effect of twist on indentation resistance

Duncan, Olly; Chester, M.; Wang, W.; Alderson, Andrew; Allen, Thomas B.

doi:10.1016/j.mtcomm.2023.105616

Cited by 3 publications

(5 citation statements)

References 68 publications

(168 reference statements)

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“…The analytical models presented here could be used in the design of auxetic foams, or adapted for other mechanical metamaterials [22,24,107,108]. These analytical models are likely to be more computationally efficient than numerical methods, as they do not require meshing and discretisation.…”

Section: Discussionmentioning

confidence: 99%

“…Alternative viscoelastic material models, such as Maxwell models, or those with strain or strain rate dependent viscosity, may also better reflect foam response [95]. To use the model with some mechanical metamaterials where foam or lattice cells approach the size of the indenter, coupled micro-morphic mechanics should also be considered [107,113,114].…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Indentation and impact response of conventional, auxetic, and shear thickening gel infused auxetic closed cell foam

Parisi

Allen

Colonna

et al. 2023

Smart Mater. Struct.

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Auxetic closed cell foams, and highly viscoelastic foams, both show potential to improve impact protection. Specifically, auxetics adapt to the shape of impacting bodies, while highly viscoelastic foams stiffen during severe impacts. So, we made auxetic closed cell foam sheets, including those that were infused with (highly viscoelastic) shear thickening gel. We then undertook comparative quasistatic and impact (drop) tests. Quasisatic tests included compression, tension and indentation. Impact tests were with a flat faced impactor at energies of 1, 3 and 5 J, and a 50 mm diameter hemisphere at 1 and 3 J. Poisson’s ratios of the foams were obtained by optical fullfield strain measurement. An analytical model was used to separate the contribution of the various measured orthotropic properties during the hemispherical impact and indentation tests. The Poisson’s ratios of the converted foams (both with and without shear thickening gel) were close to zero or marginally negative when measured through thickness. Planar values of Poisson’s ratio (measured in tension) were as low as −0.6. Through thickness Young’s moduli of the converted foams were 0.5 MPa, and planar moduli were ~12 times higher. The auxetic foams outperformed the unconverted ones during the more severe impacts, exhibiting about half the peak force during the 3 J hemispherical impacts (2.5 vs. 5 kN). The reduction in peak force was related to a measured doubling in indentation resistance for the auxetic foam. The analytical model suggests that 7 to 15% of the measured doubling in indentation resistance was due to (negative) Poisson’s ratio. Infusing the auxetic foams with shear thickening gel caused, at best, a marginal reduction in peak impact force, attributed to low and non-uniform levels of infusion.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Indentation and impact response of conventional, auxetic, and shear thickening gel infused auxetic closed cell foam

Parisi

Allen

Colonna

et al. 2023

Smart Mater. Struct.

View full text Add to dashboard Cite

show abstract

“…With high levels of control over end properties-given the additional degrees of design freedom afforded by controlling topology and base material-mechanical metamaterials are well suited to addressing complex engineering problems, like impact protection [17,50,262]. The common forms of unusual mechanical properties are auxetic (negative Poisson's ratio) behaviour (covered extensively in various reviews [46,50,307,309,345,346] and textbooks [308,347,348]), negative stiffness [349][350][351][352][353][354][355][356], shape morphing [337,[357][358][359], force/torque coupling [360][361][362][363][364], active/adaptive behaviour [351,[365][366][367], or programmable properties that are tuned to a specific application [17,26,28,341,361].…”

Section: Mechanical Metamaterialsmentioning

confidence: 99%

“…Mechanical metamaterials with force-torque coupling (known herein as twist) have seen increasing interest, since their rational design was shown in 2017 [363]. Like (negative) Poisson's ratio, twist translates axial deformation to transverse deformation-increasing resistance to indentation [360]. So, twisting mechanical metamaterials may resist penetration by concentrated loads, without shortening the stress plateau under compression (as seen for auxetics-see section 5.1).…”

Section: Force Torque Couplingmentioning

confidence: 99%

“…Clearly, in the case of foams and lattices, which have relatively large internal features (when compared to the scale of external loads), micro-morphic continuum theories often apply [360,449,450]. Where classical continuum theories cannot be used, typical approaches to designing mechanical metamaterials for impact protection are experimental, or by using microstructurally faithful numerical models [17,26,28,29,415,416,419,451], which are less efficient.…”

Section: Force Torque Couplingmentioning

confidence: 99%

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Mechanical metamaterials for sports helmets: structural mechanics, design optimisation, and performance

Haid,

Foster,

Hart

et al. 2023

Smart Mater. Struct.

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Sports concussions are a public health concern. Improving helmet performance to reduce concussion risk is a key part of the research and development community response. Head impacts with compliant surfaces that cause long duration moderate or high linear and rotational accelerations are associated with a high rate of clinical diagnoses of concussion. As engineered structures with unusual combinations of properties, mechanical metamaterials are being applied to sports helmets, with the goal of improving impact performance and reducing brain injury risk. Replacing established helmet material (i.e., foam) selection with a metamaterials design approach (structuring material to obtain desired properties) allows development of near optimal properties. Objective functions based on up to date understanding of concussion could be applied to topology optimisation regimes, when designing mechanical metamaterials for helmets. Such regimes balance computational efficiency with predictive accuracy, both of which could be improved under high strains and strain rates to allow helmet modifications as knowledge of concussion develops. Researchers could also share mechanical metamaterial data, topologies and computational models in open, homogenised repositories, to improve the efficiency of their development.

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Challenges and Advancements in Additive Manufacturing of Nylon and Nylon Composite Materials: A Comprehensive Analysis of Mechanical Properties, Morphology, and Recent Progress

Safaei,

Memarzadeh,

Asmael

et al. 2024

J. of Materi Eng and Perform

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Effect of twist on indentation resistance

Cited by 3 publications

References 68 publications

Indentation and impact response of conventional, auxetic, and shear thickening gel infused auxetic closed cell foam

Indentation and impact response of conventional, auxetic, and shear thickening gel infused auxetic closed cell foam

Mechanical metamaterials for sports helmets: structural mechanics, design optimisation, and performance

Challenges and Advancements in Additive Manufacturing of Nylon and Nylon Composite Materials: A Comprehensive Analysis of Mechanical Properties, Morphology, and Recent Progress

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