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HAL Id: hal-00993364 https://hal.archives-ouvertes.fr/hal-00993364 Submitted on 20 May 2014 HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Kirigami Auxetic Pyramidal Core: Mechanical Properties and Wave Propagation Analysis in Damped Lattice Fabrizio Scarpa, Morvan Ouisse, Manuel Collet, K. Saito To cite this version: Fabrizio Scarpa, Morvan Ouisse, Manuel Collet, K. Saito. Kirigami Auxetic Pyramidal Core: Mechani- cal Properties and Wave Propagation Analysis in Damped Lattice. Journal of Vibration and Acoustics, American Society of Mechanical Engineers, 2013, 135, pp.041001-1 - 041001-11. 10.1115/1.4024433. hal-00993364

Kirigami Auxetic Pyramidal Core: Mechanical Properties and

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Page 1: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

HAL Id: hal-00993364https://hal.archives-ouvertes.fr/hal-00993364

Submitted on 20 May 2014

HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, estdestinée au dépôt et à la diffusion de documentsscientifiques de niveau recherche, publiés ou non,émanant des établissements d’enseignement et derecherche français ou étrangers, des laboratoirespublics ou privés.

Kirigami Auxetic Pyramidal Core: MechanicalProperties and Wave Propagation Analysis in Damped

LatticeFabrizio Scarpa, Morvan Ouisse, Manuel Collet, K. Saito

To cite this version:Fabrizio Scarpa, Morvan Ouisse, Manuel Collet, K. Saito. Kirigami Auxetic Pyramidal Core: Mechani-cal Properties and Wave Propagation Analysis in Damped Lattice. Journal of Vibration and Acoustics,American Society of Mechanical Engineers, 2013, 135, pp.041001-1 - 041001-11. 10.1115/1.4024433.hal-00993364

Page 2: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r♠ ①t ♣②r♠ ♦r ♠♥ ♣r♦♣rts ♥

♣r♦♣t♦♥ ♥②ss ♥ ♠♣ tt

r③♦ r♣∗

♥ ♦♠♣♦sts ♥tr ♦r ♥♥♦t♦♥ ♥ ♥

❯♥rst② ♦ rst♦ rst♦ ❯

♦r♥ ss ♥ ♦t†

♥sttt é♣rt♠♥t é♥q ♣♣qé

❯ s♥ç♦♥ r♥

③② t♦‡

♥sttt ♦ ♥str ♥ ❯♥rst② ♦ ♦②♦ ♣♥

strt

♦r srs t ♠♥tr♥ ♠♥ ♣r♦♣rts ♥ ♣r♦♣t♦♥ r

trsts ♦ ♣②r♠ tt ♠ ①t♥ ♥ ①t ♥t P♦ss♦♥s rt♦ ♦r

♦♥trr② t♦ s♠r tt tsst♦♥s ♣r♦ s♥ ♠t ♦rs t ♣②r♠ tt sr

♥ ts ♦r s ♠♥tr s♥ r♠ r♠ ♣s tt♥ ♣ttr♥ t♥q ♥

♣♣ t♦ r rt② ♦ tr♠♦st ♥ tr♠♦♣st ♦♠♣♦sts t♦ t ♣rtr

♦♠tr② rt tr♦ ts ♠♥tr♥ t♥q t r♠ ♣②r♠ tt s♦ ♥

♥rs♦♥ t♥ ♥♣♥ ♥ ♦t♦♣♥ ♠♥ ♣r♦♣rts ♦♠♣r t♦ ss ♦♥②♦♠

♦♥rt♦♥s ♦♥ ♥t ♣♣r♦①♠t♦♥s r s t♦ t t s♦♥ss rs s♦♥

♥s ③r♦rtr ♣♦♥♦♥ ♣r♦♣rts ♥ t tr♥srs ♣♥ ♥♦ ♣r♦♣t♦♥

t♥q s ♦♥ ♦ s ♦r ♠♣ strtrs s s♦ ♣♣ t♦ t t s♣rs♦♥

♦r ♦ ♦♠♣♦st r♣♦①② tts t ♥tr♥s ②strt ♦ss ♣r♦♣

t♦♥ ♥②ss s♦s ♥s♥ rtt② t r♥t rq♥② ♥ts ♥ ♦♠♣① ♠♦

♦r t♦ ♥s ♦r♠t♦♥ ♠♥s♠ ♦ t tt

∗tr♦♥ rss sr♣rst♦†tr♦♥ rss ♠♦r♥♦ss♥♦♠tr‡tr♦♥ rss st♦st♦②♦♣

Page 3: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

tt ♣②r♠ ♦rs ♥ ♦♣ ①t♥s② r♥ t st ②rs ②

rt ♦ ♥♦ ♠t st♥ t♥qs tt ♦ ♣r♦♥ t rt② ♦ ♦st r

♥trt s♥ ♣♥s ❬ ❪ ♥ ♦ t ♠♦r trs ♦ ts tt ♦rs s t

s♣ str♥t t♦ r ♥ ♥♣♥ st♥ss ♥ s t♦ ♦♣ ♥♦

♥r② s♦r♥ ♥trt r strtrs ♦r stt ♥ ②♥♠ ♦♥ ♥ tr♠

♠♥♠♥t ❬ ❪

♣②r♠ tt ♦♥rt♦♥ ♥ tsst ♥ r ②♦t r

s ♣rtr tsst♦♥ s ①t ♥ t ♣♥ ①ts ♥ts r ss ♦ s♦s

♥ strtrs ①t♥ ♥t P♦ss♦♥s rt♦ t s♦ ①♣♥s rtr t♥ ♦♥trts

♥ ♣ ♦♥ ♦♥ rt♦♥ ①ts ❬❪ ♥ ①t♥s② st ♦r tr ♠

t♥t♦♥ ♣r♦r♠♥ ♥ ♣rtr ♦r tr t♥t② ♥ ♥♣ ♦r ❬❪ ♥

r♦st t♦r♥ ♥ ♠♦r♣♥ strtrs ❬ ❪ r tsst♦♥ s ♥ ♥

t ② r♠ t s ♣♦t♥t ♦r♠t♦♥ ♠♥s♠ ♣r♦♥ ①tt② ♥ ♣♦②♠r

♥t♦rs t r♦♠ ①❬❪r♥ ♦s ❬❪ s♠ tsst♦♥ s ♥ ♥t s

①st♥ ♥ ②♣♣rs t s♥ ♥ ♠t r♦♥ ♥♥♦ts ①t♥ s♥

♥rs♦♥ r♦♠ ♣♦st t♦ ♥t P♦ss♦♥s rt♦ ♥ st t♦ ♠♥ ♦♥

❬ ❪

r♠♥s♦♥ ♦♠♣① r s♦s ♥ s♦ ♣r♦ s♥ ♦tr ♠trs

♥ ♣rtr tr♠♦st ♥ tr♠♦♣st ♦♠♣♦sts ② ♠♥s ♦ r♠ t♥qs

r♠ s ♥ ♥♥t ♣♥s rt ♦ ♦♠♥♥ ♣②♦♥ t♥qs r♠ t t

t♥ ♣ttr♥s t♦ ♦t♥ ♥r tsst ♥ ♦♠♣① strtrs r♠ s ♥ s

sss② t♦ ♣r♦ ♦♥②♦♠s t ♥r s♣s s♥ r♦♥ ♥ r ♦♥

rs ❬❪ ①t r♥tr♥t strtrs ❬❪ ♥ ♥♦ ♠♦r♣♥ ♥♦① ♦♥rt♦♥s

❬❪ r s♦s ♦ r♠ rs♦♥ ♦ t ♣②r♠ tt ♥ rt s♥

st♥r r ♣♦①② ♣r♣r♣s ① ♦♠♣♦sts t ❯ sts t

t ♦ ♥ r♠ ♣ttr♥ r t r♦♠ s♥ ♣② ♦ t ♣r♣r ② ♥ t♦♠t ♣②

ttr r sts t ♣♦②t②♥ rs ♠ r ♦ ♥ ♦r s♣s ②

s♥ sqr r♦s ① ① ❬♠♠❪ ♠♥♠ s r r♦s r ♣t

♦♥ t r♦ss ♣♦♥ts ♦ r r♦♠ t ♣♣r s ♥ ♦tr r♦s r ♣ ♦♥

r ♦♥s r♦♠ t s ♦ r tr ♣♥ t♦tr ts r♦s ♥ r

Page 4: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

t st s ① ♥ t s♣ ♦ t ①t ♣②r♠ tt ss♠② s ②

t♣s ♥ ♥srt ♥t♦ ♠ rs rr♥♠♥t s ♣t ♥ ♥

t♦ ♦r ♠♥ts t Co t♦ r t ♣r♣r ♥ r s♠♣ s s♦♥ ♥

r

♦r sr ♥ ts ♣♣r s ♦♥r♥ t t t♦♥ ♦ t ♦♥ ♥t

♣r♦♣rts rst ♦rr ♦♠♦♥st♦♥ ♥ t t♦♠♥s♦♥ ♣r♦♣t♦♥ ♦ t

r♠ ♣②r♠ tt ♦♥ ♥t ♣♣r♦①♠t♦♥ s s t♦ r t t

strssstr♥ t♥s♦r ♦ t ♦♠♦♥s tt ♥ t♦ t t s♦♥ss rs r♦♠ t

♥ ♣r♦♠ ss♦t t♦ t rst♦s qt♦♥ ♥ r♦s ♣♥s rt♦♥

♥ t st② ♦ t s♦♥ss rs s t ♥tt♦♥ ♦ ♣♦ss ♥♦♠♦s ♦r

♦ tr rtr rtr ♦ t s♦♥ss sr s ♥ st s ♠trs t♦

♥t② sts ♥ ♣♦♥♦♥ ♠♥ r t sts r ♠sr s ♣r♦ ♥s ♦♥

t s♦♥ss sr ❬❪ ❩r♦s♦♥ss rs r tr♦r s②♠♣t♦♠ ♦ ♣♦ss s♦t♦♥s

rt t t♦r s ♦r♥t ♦♥ ♥s ♦rrs♣♦♥♥ t♦ ts ♥stt②

♣♦♥ts ♦ t st ♦ t t♦rs ♥♦ ♥ ①t♥s st② ♦ t ♦♠♦♥s

♠♥ ♣r♦♣rts rst ♦rr ♦♠♦♥st♦♥ ♥ s♦t♦♥s ♦ t rst♦ qt♦♥

♦ t ♣rtr ♣②r♠ tsst♦♥ s♦♥ ♥ r s ♥♦t ♥ ♣r♦r♠ ②t ❲

s♦ tt t tt s ①t ♥ t ♣♥ t s♦ ♣♦ssss♥ ♣r ♠♥

♦r r t ♥♣♥ st♥ss s r t♥ t tr♥srs ♦♥ ♦♥trr② t♦ ss

♥trs②♠♠tr ♦♥②♦♠ ♦♥rt♦♥s ①st♥ ♥ ♦♣♥ trtr r♠ tt

♦s s♦ ♥ ③r♦ rtr s♦♥ss rs ♥ t tr♥srs ♣♥ ♣♥♥ ♦♥ t

♦♠tr ♣r♠trs ♥♥ t tt ♦r♦r ♦♥sr s♦ t s s ♥ t

r ♥♥r♥ ♣♣t♦♥ r ②strt ♠♣♥ s ♣rs♥t ♥ t s②st♠ t♦

t ♥tr♥s ♦ss t♦r ♦ t ♣r♣r s t♦ ♠♥tr ts tts ♥♦

♣r♦♣t♦♥ t♥q s ♣rs♥t ♥ ts ♦r t♦ ♦♥sr t t ♦ t ♠♣♥ ♥ t

tt ♥ ♥t② t rtt② ♦ ♥s♥ ♠♦s ♣rs♥t t r♥t rq♥s

❲ t ♦♥ ♥t ♣♣r♦①♠t♦♥ ♦s ♥♦t r ♥② ♥s ♣r♦♣t♦♥

♣ttr♥ ♥ t ♣♥ ♦ t tt t ♠♣ ♣r♦♣t♦♥ t♥qs t

t ♦♠♣① ♠♦ ♦r ①st♥ t♥ t ♠♥ts ♦ t ♥t strtr ♥

t ♥s♥ rtt② t♦ s♣ ♠♦s ss♣t♥ ♠♦r ♥r② t♥ t ♦trs

Page 5: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r Pr♦t♦♥ ♦ ♣②r♠ tt ♦r s♥ ♣r♦rt♦♥r♦♥♦♥ t♥q

♦♥ ♠ts r♦♠ ❬❪

r t♣s ♦ t ♠♥tr♥ ♦r t r♠ ①t ♣②r♠ tt ♦r

Page 6: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♥ ♦♠♦♥st♦♥

q♥t ♠♥ ♣r♦♣rts ♦ t r♠ tt strtr ♥ ♦♠

♣t s♥ ♥t♠♥t s ♦♠♦♥st♦♥ t♥qs ♦r ♣r♦ ♠ ❬❪ ♥

♣r♦ ♠♠ t ♥rs ♥♦ s♣♠♥t t♦r u ♥ ①♣rss s

u = ǫx+ u′ r ǫ s ♥ ♣♣ str♥ ♥ u′ s♦② tt♥ ♣r♦ ♥t♦♥

♦ u rt♦♥ tt♦♥ t♦ ♥t② u′ s ①♣rss ② ❬❪

v′T [K] u′ = v′T F

❲r v′ s ♥♦tr ♣r♦ tt♥ ♥t♦♥ s♦♥ qt♦♥ [K] s t

st♥ss ♠tr① ♦ t s②st♠ ♥ F s t♦r ♦ ♥rs ♥♦ ♦rs ♦r♥ t♦

st♥r t♥qs t st♥ss ♠tr① s ♥ s

[K] =∑

e

[k]e =1

V

ˆ

e

[B]T [C] [B] dV

♥ [B] ♦♥t♥s t s♣t rts ♦ t s♣ ♥t♦♥s [C] t s♦♥ ♦rr

strssstr♥ t♥s♦r ♦ t ♠tr ss♦t t♦ t eth ♠♥t ♥ V t ♦♠ ♦ t

♦r ♠♦ ❲♥ ♣rsr str♥ ǫ s ♠♣♦s t ♥rs ♦r t♦r F♥ ①♣rss s

F = −[

K]

ǫ

❲r

[

K]

=∑

e

[

k]

e=

1

V

ˆ

e

[B]T [C] dV

♥srt♥ ♥ ♥ ♦♥ ♦t♥s t ♦♠♦♥s strssstr♥ t♥s♦r rt♦♥s♣

r♣rs♥t♥ t q♥t ♠tr ♥♦s ♥ t ♦♠ V

[

C]

ǫ = σ

❲r σ s t ♦♠ r t♦r ♦ t strsss σij, i, j = 1 . . . 6 ♦r t r♣

rs♥tt ♥t ♦ t ♣r♦ ♠r♦strtr ♦♠♦♥s ♦♠♣♥ ♠tr①

Page 7: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

[

S]

=[

C]−1

s q ♦r tr♥srs s♦tr♦♣ ♠tr s

[

S]

=

1Ex

−νyxEx

−νzxEx

0 0 0

−νxyEy

1Ey

−νzyEy

0 0 0

−νxzEz

−νyzEz

− 1Ez

0 0 0

0 0 0 − 1Gxz

0 0

0 0 0 0 1Gyz

0

0 0 0 0 0 1Gxy

r♣rs♥tt ♥t ♠♥t ❱ s ♦r t r♠ ♣②r♠ tt s

s♦♥ ♥ r ♣②r♠ tt s sr s♥ t ♥♦♥♠♥s♦♥ ♣r♠

trs α = a/b β = t/l δ = l/b ♥ ♥tr♥ ♥ θ ♥ s♦tr♦♣ ♥♣♥ ♠♥

♦♥rt♦♥ s ♦r α = 1 ♣r♠tr δ ♥ts ♦ r t ♦r ♦ t

♠♥t l ♣rts r♦♠ ♠ strtr ❲t♥ t ♦♥t①t ♦ ts ♦r ♦♥② ♥

♣♥ s♦tr♦♣ ♦♥rt♦♥s α = 1 ♥ ♦♥sr ♠♦ ♦ t ♥t

s ♥ ♦♣ s♥ t ♦♠♠r ♦ ❨ r r♠♥s♦♥

strtr ①r ♠♥ts t r♥♥ ♥tr♣♦t♦♥ ♥t♦♥s ♥♦s

♥ s ♥ s t♦ r♣rs♥t t ♣②r♠ strtr t ♥♦r♠ ♠s s③

q♥t t♦ t/2 ss♠ tr ♠s ♦♥r♥ tst ♣r♦ ♦♥r② ♦♥t♦♥s

❬❪ ♥ ♣♣ t♦ t s xy ♦♥ t ♥t t ♠♥♠♠ ♥ ♠①♠♠ z

♦♦r♥ts ♥ ♣t r ♦ ♠♣♦s s♣♠♥ts ♦rrs♣♦♥♥ t♦ ♥♦r♠ str♥s

s t♦ r♣rs♥t ♥ ♥♥t ♣r♦ ♦r ♠tr ♦r s♥ strtrs ♥ tr♦r

♣r♦t② ♥ t xy♣♥ ♦♥② ♥t str♥s t t ♦♥r②

ǫx ǫy ǫz γxz γyz γxy

T

♥ ♠♣♦s s s♣♠♥t s ♥ t♦ stt ♥r ♣r♦♠ s♦ t

t♦♥♣s♦♥ s♦r ♣♥♥ ♦♥ t s♣ ♦♠♥t♦♥ ♦ ♥♦♥♠♥s♦♥ ♦♠

tr② ♣r♠trs s t ♠♦s s③s r♥♥ t♥ t♦ s s

♠♥ ♣r♦♣rts ♦ t ♦r r r♣rs♥tt ♦ r ♦♥ r ❬❪

t ❨♦♥s ♠♦s Ec = 30GPa P♦ss♦♥s rt♦ νc = 0.4 ♥ ♥st② ρc = 1600 kgm−3

♦r t s♠t♦♥s t ♥t ♦ t rs l s ss♠ ♦♥st♥t t ♠♠ t

rt ♥st② β s ♠♣♦s q t♦ t♦ ♦ sr ♦r♠t♦♥ ♦♥trt♦♥s r♦♠

t r♦ssst♦♥ ♦ t rs ♥ ss♠ t♥ ♠ ♦r ♣t strtrs ♥ ♣rs♥t

♥ t r♠ tt ♦♥sst♥t t♦ s♠♣s ♣r♦ t t ♠♥tr♥ ♣r♦ss

s♦♥ ♥ r

Page 8: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

rst♦s qt♦♥s

s♦♥ss rs ♥ s♠t r♦♠ t s♦t♦♥ ♦ rst♦s qt♦♥s ♦r

♥ k ♣r♦♣t♦♥ rt♦♥ t qt♦♥s t ♦rrs♣♦♥♥ ♥ ♣r♦♠

❬ ❪

[Γ] A = γ A

❲r Γ = kicijklkl ♥ γ = ρv2 cijkl ♥ts t ♦♠♦♥s ♦rt♦rr strss

str♥ t♥s♦r ♦ t q♥t ♠tr ♦ t ♣②r♠ ①t tt tr♠♥♥t

♦ qt t♦ ③r♦ ②s tr ♥s ♥ tr♠s ♦ ρv2 (k) ♥ t♦ tr s♦♥ss

rs s (k) = 1/v (k) ss♦t t♦ |k| = 1 ❬❪ ♦♥sr♥ t t♦r k ♣r♦♣t♥

♥ t xz ♣♥ t k = cos (φ)k+sin (φ) i i,k ♥ t ♥t rs♦rs ♦ t x ♥ z ①s

rs♣t② t ♠tr① Γ♥ ♥ rst ♦r t tr♥srs s♦tr♦♣ ♠r♦strtr s

❬❪

[Γ] =

c55 + (c11 − c55) sin2 φ 0 (c13 + c55) cosφ sinφ

0 c44 + (c66 − c44) sin2 φ 0

(c13 + c55) cosφ sinφ 0 c33 + (c55 − c33) sin2 φ

❲♥ t st ♦♥st♥ts r ♥♦r♠s ♥st c11/√ρ ρ ♥ t ♥st② ♦ t

♦♠♦♥s ♠tr t tr ♥s γi t s♦♥ss rs si (φ) = v−1i (φ) =

γ−1/2i (φ) ♥ t xz ♣♥

♦r ♣r♦♣t♦♥ ♥ t xy ♣♥ k = cos (φ) j+ sin (φ) i t i, j t ♥t

rs♦rs ♦♥ t x ♥ y rt♦♥s rs♣t② t Γ ♠tr① ss♠s t ♦♦♥ ♦r♠

❬❪

[Γ] =

c11 cos2 φ+ c66 sin

2 φ (c12 + c66) cosφ sinφ 0

(c12 + c66) cosφ sinφ c66 cos2 φ+ c22 sin

2 φ 0

0 0 c55 cos2 φ+ c44 sin

2 φ

s♦♥ss rs si (φ) = γ−1/2i (φ) ♥ s♦ t ♥♦r♠s♥ t ♦♥ts

♥ ② c11/√ρ ♥s ♦ ♥ t s♥ t tt r♦t♥

t t t♥s♦r ♦♥ts cij ♦t♥ r♦♠ t ♦♠♦♥st♦♥ ♣r♦r sr

Page 9: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♦qt ♥ ♦ t♦r♠s ♦r st♦②♥♠ s♣rs♦♥ ♥②ss

t♠t r♠♦r

t s ♦♥sr ♥ ♥♥t ♣r♦ st♦②♥♠ ♣r♦♠ s ♣rs♥t ♥ r

r♠♦♥ ♦♠♦♥♦s ②♥♠ qr♠ ♦ s②st♠ s r♥ ② t ♦♦♥ ♣rt

rt qt♦♥

ρ(x)ω2w(x) +∇C(x)∇sym(w(x)) = 0 ∀x ∈ R3

r w(x) ♥ R3 s t s♣♠♥t t♦r C(x) st♥s ♦r t ♦♦ stt② t♥s♦r

♥ ε(x) = ∇sym(w(x)) = 12(∇wT (x) + w(x)∇T ) s t str♥ t♥s♦r ② ♦♥sr♥

♣r♠t ♦ t ♣r♦ ♣r♦♠ ΩR ♥ ② s♥ t ♦ t♦r♠ t ss♦t

♦ ♥♠♦s ♥ t s♣rs♦♥ ♥t♦♥s ♥ ♦♥ ② sr♥ t ♥ s♦t♦♥s

♦ t ♦♠♦♥♦s ♣r♦♠

w(x) = wn,k(x,k)eik.x

r wn,k(x,k) r ΩR♣r♦ ♥t♦♥s ♥ tt s wn,k(x,k) ♥ ωn(k) r t

s♦t♦♥s ♦ t ♦♦♥ ♥r③ ♥s ♣r♦♠ ♦ t st ♦♣rt♦r s

sr ♥

ρ(x)ωn(k)2wn,k(x) +∇C(x)∇sym(wn,k(x))

−iC(x)∇sym(wn,k(x)).k − i∇C(x)12(wn,k(x).k

T + k.wTn,k(x))

+C(x)12(wn,k(x).k

T + k.wTn,k(x)).k = 0 ∀x ∈ ΩR

wn,k(x−R.n)−wn,k(x) = 0 ∀x ∈ ΓR

t s ♦♥sr t ♣rt rt qt♦♥s ♦♥ ♥t ΩR t ①♣rss♦♥

st♥s ♦r ♥r③ ♥ ♣r♦♠ ♥ t♦ ♦♠♣tt♦♥ ♦ t s♣rs♦♥ rs

ωn(k) ♥ ♦rrs♣♦♥♥ ♦qt ♥t♦rs wn,k(x) ♦r ♣♣t♦♥s t

t♦rs r s♣♣♦s t♦ ♦♠♣① ♠♣♥ tr♠s r ♥t♦ qt♦♥ ♥ ♥

tr♦r rtt♥ s k = k

sin(θ) cos(φ)

sin(θ) sin(φ)

cos(θ)

= kΦ r θ ♥ φ r♣rs♥t t rt♦♥

Page 10: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♥s ♥t♦ t r♣r♦ tt ♦♠♥ ♥ Φ s t rt♦♥ t♦r s ♦♠♣♦st♦♥

ss♠s tt r ♥ ♠♥r② ♣rts ♦ t t♦r k r ♦♥r

tr t♥ ♥t♦ ♦♥srt♦♥ t ♣r♦t② ♦♥t♦♥s ♥ rr♥♠♥ts

♦r♠t♦♥ ♦ t ♣r♦♠ ♥ rtt♥ s

∀wn,k(x) ∈ H1(ΩR,C3)/wn,k(x−Rn) = wn,k(x) ∀x ∈ ΓR ,

´

ΩRρ(x)ω2

n(k)wn,k(x)wn,k(x)− εn,k(x)C(x)εn,k(x)

+ikκn,k(x)C(x), εn,k(x)− ikεn,k(x)C(x)κn,k(x)

+k2κn,k(x)C(x)κn,k(x)dΩ = 0

♥♠r ♠♣♠♥tt♦♥ s ♦t♥ ② s♥ st♥r ♥t ♠♥ts ♠t♦ t♦

srts t ♦r♠t♦♥ ss♠ ♠tr① qt♦♥ s ♥ ②

(K + λL(Φ)− λ2H(Φ)− ω2n(λ, (Φ)M )wn,k(Φ) = 0

r λ = ik M ♥ K r t st♥r s②♠♠tr ♥t ♠ss ♥ s②♠♠tr s♠

♥t st♥ss ♠trs rs♣t② L s ss②♠♠tr ♠tr① ♥ H s s②♠♠tr

s♠♥t ♣♦st ♠tr①

M →ˆ

ΩR

ρ(x)ω2n(k)wn,k(x)wn,k(x)dΩ,

K →ˆ

ΩR

εn,k(x)C(x)εn,k(x)dΩ,

L →ˆ

ΩR

−κn,k(x)C(x)εn,k(x) + εn,k(x)C(x)κn,k(x)dΩ,

H →ˆ

ΩR

κn,k(x)C(x)κn,k(x)dΩ

❲♥ k ♥ Φ r ① t s②st♠ s ♥r ♥ ♣r♦♠ t s♦t♦♥ ♦

♦s ♦♠♣t♥ t s♣rs♦♥ ♥t♦♥s ω2n(k,Φ) ♥ t ss♦t ♦ ♥

t♦r wn,k(Φ)

s ♣♣r♦ s ss② s ♦r ♦♠♦♥③t♦♥ s♣tr s②♠♣t♦t ♥②ss ❬❪

♥ t ♦♥t①t ♦ ♣r♦♣t♦♥ s♣rs♦♥ rtrsts ♥ r ♥ ♦qt

♣r♦♣t♦rs r ♣rrr ♦r ♦r qs ♦♠♣tt♦♥ s ♥t ② ❬❪ ❬❪ ♦r

❬❪ ♦st ♦ t t♠ ts t♥qs r ♣♣ ♦r ♥♠♣ ♠♥ s②st♠s

r♣rs♥t ② st ♦ ♦♥st♥t ♥ r ♠trs ss ♣♣r♦ ♦♥ssts ♥ s♥

♠s ♦ t r ks♣ k ♦r λ ♥ Φ ♥s t rst r♦♥ ③♦♥ ♦r ♦t♥♥

t ♦rrs♣♦♥♥ rq♥② s♣rs♦♥ r♠s ♥ t ss♦t ♦qt t♦rs ♦r

Page 11: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♥♠♣ s②st♠s ♦♥② ♣r♦♣t♥ ♦r ♥s♥t s ①st ♦rrs♣♦♥♥ t♦ ♠s ♦

♥s♦t♦♥s ♣r② r ♦r ♠♥r② sr♠♥t♦♥ t♥ ss ♦ s s qt

strt♦rr ♠♣ s②st♠ s ♦♥sr ♠trs K, L, H r ♦♠♣①

t ♥s♥t ♣rt ♦ t ♣r♦♣t♥ s ♣♣r s t ♠♥r② ♣rt ♦ ω2n(λ,Φ) ♥

rs t t♥ ♦♠s r② t t♦ st♥s t t♦ ♠s ♦ s t s♦ t♦

♦♠♣t t ♦rrs♣♦♥♥ ♣②s s ♠♦♠♥ts ② ♣♣②♥ s♣t ♦♥♦t♦♥

t s ♣♦ss t♦ rrr♥ t s②st♠ ♥ ♦rr t♦ t ♥t♦ ♦♥t ♠♣♥ ts ❬❪

s ♦r♠t♦♥ s♦ ♣r♦s st ♦♥t♥ts ♦r t♠s♣ ♦♥♦t♦♥ ♥ ♦r t

♦♠♣tt♦♥ ♦ s♦♥ ♣r♦♣rts s ♥ ② ❬❪ ♦r ❬❪ t ♦♥ssts ♥ ♦♥sr♥ t

♦♦♥ ♥rs ♥ ♣r♦♠

(K − ω2M ) + λn(ω,Φ)L(Φ)− λ2n(ω,Φ)H(Φ))wn,k(Φ) = 0

♥ ts ♣r♦♠ t ♣st♦♥ ω ♥ t ♣r♦♣t ♥ Φ r ① r ♣r♠trs

❲s ♥♠rs λn = ikn ♥ ss♦t ♦qt t♦rs wn,k r t♥ ♦♠♣t ② s♦♥

t qrt ♥ ♣r♦♠ s ♣♣r♦ ♦s t♦ ♥tr♦ rq♥②♣♥♥t

♠trs ♦rrs♣♦♥♥ t♦ ♥r③ ♠♣♥ tr♠s s♦stt② ♠t♣②ss ♦♣♥

tr♦♠♥ t tr♦♥ ♦r♥r② r♥t qt♦♥ ♦♠ ♦tr ♠♦

♦r ♦♣♥ ♦♠♥ ♦♥r② ♦♥t♦♥s ♦♠♠r ♦♥t♦♥ s ♦♥ ts ♣♣r♦ ♥

♥rs ♦rr tr♥s♦r♠t♦♥ ♥ t ks♣ ♦♠♥ s t♦ t t ♣②s s

s♣♠♥ts ♥ ♥r② s♦♥ ♦♣rt♦r ♥ t ♣r♦ strt♦♥ s ♦♥♥t t♦

♥♦tr s②st♠ ❬❪ ♥♦tr t♠♣♦r ♥rs ♦rr tr♥s♦r♠t♦♥ ♥ ♣r♦ ②

t♦ ss s♣t♠♣♦r rs♣♦♥s ♦r ♥♦♥♦♠♦♥♦s ♥t ♦♥t♦♥s s L s s

s②♠♠tr t rst♥ ♥s r qr♣ λ, λ,−λ,−λ ♥ ♦♣s♥ ♥t♦ r

♦r ♠♥r② ♣rs ♦r s♥ ③r♦ ♥ ♠trs r r ♦r ♥♠♣ s②st♠s ♥

t ♥r ♠♣ s ♦♥ ♦t♥s ♣r ♦ r ♥s ♦rrs♣♦♥♥ t♦ ♥s♥t

♠♦s ♦r♥t ♥ t♦ ♦♣♣♦st rt♦♥s ♦♥ t ks♣ ♥ ♠♥r② s t♦ t♦

tr♥ s ♣r♦♣t♥ ♥ ♦♣♣♦st rt♦♥ ♥s♦t♦♥s r s♠r t♦ t♦s

♥ ② t ♠t♦ ♥ ♦r ♦♠♦♥♦s ♠tr ♥♦♥ ♣r♦ ♥ t♦♥

♠♣♦rt♥t ♣r♦♣rts ♥ ①tr♣♦t r♦♠ ❬❪ t② ♦ t ♠t♦ ♣r♦♣♦s

♥ ts ♦r s ♥ ♣r♦ t sr tst ss ♥ ❬❪

s ♣r♦s② ♠♥t♦♥ t r ♣rt ♦ k = kΦ t♦r s ss② rstrt t♦ t

rst r♦♥ ③♦♥ ♥ t qrt ♥ ♣r♦♠ t t② ♦ t ♦♠♣t

Page 12: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

s♦t♦♥ s ♥♦ ♦♥r ♦♥♥ t♦ s♣ r♦♥ ③♦♥ ♦r rt♦♥ t♦rΦ ♦rt♦♦♥

t♦ t tt ts ♦r Φp1 = [1, 0]T ♥ Φp2 = [0, 1]T ♥ rt♥r t

♣r♦ ♦♥t♦♥s ①♣rss ♦r ♦♥ ♠♥s♦♥ r st λj(Φp) s

♥ ♥ ss♦t t♦ wj,k(Φp) t♥ ∀m ∈ Z3, λ + i.ΦTp (G.m) s s♦ ♥ ♥

ss♦t t♦ wj,k(Φp)e−i.ΦT

p (G.m)x s ♦r ♥♠♣ s②st♠s t ♥s r

♣r♦② strt ♥ t ks♣ ♦♥ ts ♣r♥♣ rt♦♥s

♦♠♣tt♦♥ ♦ ♥s♥ ♥ ♠♣ ♣♦r ♦ rtr

♥ ♠ ♦ ts ♦r s t♦ ♣r♦ ♥♠r ♠t♦♦♦② t♦ sr t ♣rtr

♦r ♦ t ♥r② ♦ ♥t♦ t ♣r♦② r♠ ①t ♦r ♥ tr♦r ♥s

t♦ ♥ st ♥t♦r ♦r st♥s♥ ♣r♦♣t ♥ ♥s♥t ♦r s♣②

♥ ♠♣ s②st♠ s ♦♥r♥ ♣t② ♦ ♥ ♦ t♦ tr♥s♣♦rt ♥r②

s ♥ ② ts r♦♣ ♦t② ♥ts ♦ ♥r② s tr♥s♣♦rt ♥t♦ t ♦♥sr

s②st♠ ♦♥ s♦ t♦ st♥s t♥ ♣r♦♣t ♥ ♥s♥t s ♦

♥ s♦t♦♥ un(ω, φ), kn(ω) s ♦♥sr t ss♦t r♦♣ ♦t② t♦r ❬❪

s ♥ ②

Cgn(ω, φ) = ∇kω =〈〈S〉〉〈〈etot〉〉

=〈I〉

〈Etot〉

❲r 〈〈:〉〉 s t s♣t ♥ t♠ r rs♣t② ♦♥ ♦♥ ♥ ♦♥ ♣r♦ ♦

t♠ s t ♥st② ♦ ♥r② ♦ I t ♠♥ ♥t♥st② ♥ etot Etot t t♦t ♥r② ♥

ts t♠ r ♦♥ ♣r♦ s ❭t④②s♥♦r⑥ ♦r ts

♥t♥st② t♦r I s ①♣rss s

〈In〉 = −ω

2Re

Ωx

C(εn(x) + ikΞn(x)).(w∗n(x))

Vol

)

❲r .∗ s t ♦♠♣① ♦♥t Re st♥s ♦r r ♣rt ♥ Vol ♦r t ♦

♠♥ ♦♠ s t s♣t♠♣♦r r ♦ t s②st♠ r♥ s ♥ s

❭t④②s♥♦r⑥ t t♦t ♥r② r s ♣♣r♦①♠t ② ♦♥② ♦♠♣t♥

t ♥t ♥r② r

〈Etot〉 =1

2Vol

(

ˆ

Ωx

ρω2wn(x, ω, φ).w∗n(x, ω, φ)dΩ)

Page 13: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r♦♣ ♦t② t♦rs Cgn(ω, φ) r ♦♠♣t ♦r ♥♠rs t rq♥②

st s ♦r t r♠ ♣②r♠ tt

♣r♦♣♦s ♠t♦♦♦② s s t♦ st② t s♣rs♦♥ ♥t♦ ♠♥s♦♥

r♠ ①t tt t ♦♥ssts ♦ ♥ ♥♥t ♣r♦ ♠♥s♦♥ ♠

♦ ♣r♦ strt♦♥ ♦ t ♥tr② ♣rs♥t ♥ r s②st♠ s ♠ ♦

2.5mm t ♣t ss♠② ♠ ♦ s♦tr♦♣ ♠♣ ♥♦♥♦♥ r ♣♦②♠r t t

s♠ ♠♥ rtrsts s ♦r t ♦♠♦♥st♦♥ ♦ ♦♥sr t ♥tr♥s

♠tr ♠♣♥ ♦ t ♦r ♠tr ♥ ②strt ♠♣♥ t♦r ♦ 0.001 s ♥ s

s♠ ♦♥sst♥t t♦ ②strt ♦ss t♦rs ♦ tr♠♦st♣♦①② ♣r♣rs ❬❪ s③

s 120mm2 ♠t♦ ♦s s t♦ ♦♠♣t ♥ rq♥s ♦rrs♣♦♥♥ t♦ ♥② k

t♦r sr ♥ ②♥r ♦♦r♥ts s②st♠ ② ts rs k ♥ ts ♥ φ ♥ t ♦

rst r♦♥ ♦♠♥ ♥♠r ♠♣♠♥tt♦♥ s s ♦♥ t ♦r♠

t♦♥ s♥ ♠♥s♦♥ ♦r♥tt♦♥ ♥ t ks♣ ② ♠♣♦s♥ Φ =

cos(φ)

sin(φ)

0

♣♣ ♦♥r② ♦♥t♦♥s r qts ♦ s♣♠♥ts ♦♥ t t♦ ♣rs

♦ tr s Γr+1Γr−

1andΓr+

2Γr−

2♦♥ ♦♥rs ♦ ♠♣♦s s rt ♦♥

r② ♦♥t♦♥s ♥ ①trs♦♥ ♦♣♥ r ♠♣s ♦ s♣♠♥ts r♦♠ t s♦r

s ①♣♦rt t♦ t st♥t♦♥ ♦rrs♣♦♥♥ t♦ t ♦♣♣♦st ♦♥ r♦♠ Γr+1toΓr−

1

s t ♦♠♥s r ♦ t s♠ s♣ ♠♥s♦♥ t②♣② s ♣♦♥ts ♠♣♣♥

①♣♦rt ♠♣♣♥ s s♦ ♦♣ t♦ t st♥t♦♥ s♣♠♥t ② s♥ t

r♥ ♠t♣rs ♠♣♠♥tt♦♥ s ♠ t t♣②ss ♣t♦r♠

♥ ♣r♠tr ♦♠♣tt♦♥ t♦ ♦t♥ k(ω, φ) s rr ♦t t t r♦t♥s ♦r

♣r♠trs ω andφ t qrt ♥ ♣r♦♠ ♥ r♦r♠t s rst

♦rr ♦♥ ② ♦♥ t stt ♠♥s♦♥ tr ♦♥str♥t ♥♥ t s ♣♦ss t♦ rt

t s②st♠ ♥ t ♦r♠ Ax = λBx ♦rt♠ ♦♠♣ts t rst ♥

s ♦ t ♠tr① C = A−1B ♦ ♦ ts t s♦r ss t P

r♦t♥s ♦r rs ♥ ♣r♦♠s s sr ② ❬❪ s ♦ s s

♦♥ r♥t ♦ t r♥♦ ♦rt♠ t ♠♣t② rstrt r♥♦ ♠t♦

P r♦t♥s ♠st ♣r♦r♠ sr ♠tr①t♦r ♠t♣t♦♥s Cv

Page 14: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r ♦♠♣s r ② s♦♥ t ♥r s②st♠ Ax = Bv s♥ t P

s♦r ♦♣ ② ❬❪ s ♣r♦r ss ♦ ♣rs♦♥ ♦t♥ ♣♦♥t ♥♠rs ♥ s

♠♣♠♥t s♥ ♦t ♦ ♦r ♠♠♦r② ♠♥♠♥t ♥ ♦rr t♦ ♦ ♥② ♠♠♦r② ♣r♦♠

♥ ♥ ♥s ♥ ♦♥r ♠s s ♦♥sr r rst ♠s s ♦♥ssts

♦ ttrr r♥ qrt ♠♥ts ♦r rs ♦ r♦♠ ♥ t r♥

♦♥ ♦ ttrr r♥ qrt ♠♥ts ♦r rs ♦ r♦♠ ♥ t

tst ss ♦♥sr t♥ ts ♦r t rq♥② r♥ s ω = 2π.[1000 : 1000 : 10000]

t♥ ③ ♥ ③ ♥ φ = [0 : π20

: π2]

♥ ♣r♦♣rts

r s♦s t rt♦♥ ♦ t ♥♣♥ P♦ss♦♥s rt♦ νxy q t♦ νyx ♦r s②♠♠tr②

rs♦♥s ♦r r♥t δ s t r②♥ ♥tr♥ ♥s β = 0.05 ①t ♥t

P♦ss♦♥s rt♦ ♦r ♦ t r♠ tt s ♥t ♦r t θ r♥ ♦♥sr ♣rt

r♦♠ r② s♠ θ < 2o ♥ r θ > 78o ♠ ♥s ♥t ♦♥rt♦♥s r t

♠♥ts l t♥ t♦ ♠♦st t ♦r③♦♥t ♥s r rt t♦ ♦♥rt♦♥s

r t ♠♥ts t♥ t♦ st♥ ♣rt rt ♥ ♦t ss t ♠♥ts l t♥ t♦

♦♠♥t ② ① ♦r♠t♦♥ ♠♥s♠s ♦♥trt s♥♥t② t♦ ♦r♥

♦♥ t P♦ss♦♥s rt♦ s ♥ ♥trs②♠♠tr ♦♥②♦♠ ss♠s t rs ♥

①r ♦r ❬❪ t♥ 10o ♥ 30o t P♦ss♦♥s rt♦ t♥s t♦ ts st

♠♥t ∼ −0.9 ♦r δ = 5.0 t♥s t♦ rs s s♦♦♥ s t strt♥ ts ♦

t ♠♥ts strt t♦ ♣rs♥t ♥ t ♠r♦strtr ♠♦r t ♠♥t s♦ ss♠s

♣t s♣ ♦r♥ δ s t ♦r t ♠♥t ♦ t ♥♣♥ P♦ss♦♥s

rt♦ t t ♠♥♠♠ ♥♦ r t ♦r ♥tr♥ ♥ νxy = −0.6 ♦r

δ = 1.0 ♥ t ♦♥trr② t ♦t♦♣♥ P♦ss♦♥s rt♦ νxz r s ②s ♣♦st

r♥♥ t♥ ♥ t s♠♠♦♥♦t♦♥ rs t t ♥tr♥ ♥

♠♦r ♣r♦♥♦♥ t ♣t rs l δ = 1.0

r s♦s t rt♦♥ ♦ t ♥♣♥ Ex = Ey ♥ ♦t♦♣♥ Ez ❨♦♥s

♠♦s rss t ♥tr♥ ♥ ♦r t♦ r s♣t rt♦s δ = 1.0 ♥ δ = 3.0 ♥

♠♣♦rt♥t s♣t t♦ t s t t tt t tr♥srs st♥ss s ♦r t♥ ♥ t

Page 15: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♥♣♥ ♦♥ ♦r r② s♠ ♥s ♥st r♠ ♦ r t rt♦ Ex/Ez s ♦r

δ = 1.0 ♦r θ > 20o t rt♦ ♥ r② t♥ ♥ t♠s ♦r st♥ss rt♦s r

♦sr ♦r ♥rs♥ δ s s ♦r s ♥s ♦r ss r strtrs

♦ s♦ ♥r s♥ rss β ♦ t tr♥srs ♠♥ ♣r♦♣rts t ♥

♣♥ ♦♥s s t β3 ❬❪ ♦r t r♠ ♣②r♠ tt ♥ t♦t s

♣rs♠t ♦♥②♦♠ st♦♥ r t rs ♦r♠ ♥r ♥♥ t xy♣♥

♣r♦♣rts r ♦♠♥t ② ♠♠r♥ ♥ sr ♦r♠t♦♥s ♦ t rs l ♥ tt s♥s

t ♣②r♠ tt ♦♥sr ♥ ts ♦r s ♥trs②♠♠tr ♦♥②♦♠

t ts ♣rs♠t r♦ssst♦♥ s s tr♦tt♥ss r♥♦r♠♥t ♥ ♠♦r

♣r♦♥♦♥ rt♦ t♥ ♥♣♥ ♥ ♦t♦♣♥ sr ♥ ♦sr ♥ r

r Gxy/Gxz rt♦s ♣ t♦ ♥ ♦sr ♦r θ < 3o ♥ δ = 1.0 ♥trst♥② ♦r

♦t δ ♦♥rt♦♥s ♦♥ ♥ ♦sr tr♥srs sr st♥ss ♥rs♦♥ ♦ θ = 55o

r t ♦t♦♣♥ sr ♠♦s ♦♠s r t♥ t ♥♣♥ ♦♥ s ♦r

s ② t♦ ♦♥t t♦ ♥rs♥ ♥trt♦♥ t♥ t ♠♠r♥ st♥ss t♥

t rs l ♥ t ♥♥ ♦♥ ♥ t ♣ts b t t s ♦ t ♥t r

t♥s t♦ qs ♦r s♣ ♥ ♥ δ t ♦♥st♥t α

♦♥ss rs

r s♦s t s♦♥ss rs ♥ t xz ♣♥ q ♦r s②♠♠tr② ♥ t yz ♣♥

♦r δ = 1.0 r ♥ δ = 5.0 r t ♦♥st♥t ♥tr♥ ♥ θ =

20o t tr s♦♥ss r s3 (φ) s♦s r② str♦♥ rtt② t φ = 0, π/2, π, 3π/2

♦rrs♣♦♥♥ s♦ t♦ t ♠♥ ①s ♦ t rs l rst t♦ s♦♥ss rs s1 (φ) ♥

s2 (φ) ♦r ♠♦r ♥trst♥ ♦r t ♥r ③r♦s♦♣ t♥ 55o <

φ < 135o ③r♦s♦♥ss s ♦r ♥ tr♠s ♦ r♥ ♦r t s♦♥ s♦♥ss r ♥

♣♥s ♦♥ t r s♣t rt♦ δ ❲ r♥ ♥ tr♠s ♦ ♥ φ r♥ ♦r t

③r♦s♦♣ ①sts ♦r t tt t δ = 1.0 t s1 (φ) r s♦s t s♦♣ ①t♥♥

♠♦st t♥ 20o < φ < 160o ♦r rs l ss♠♥ ♠♦r ♠ strtr δ = 5.0

♥ ♥♦r♠s tr♠s t s♦♥ s♦♥ss r ♥ δ = 1.0 ♦rrs♣♦♥s t♦ r ♦ts

v s♦t♦♥s ♦ t rst♦s qt♦♥ t♥ t ♦♥s ♦r t tt ♦♥rt♦♥

t δ = 5.0 ①st♥ ♦ ③r♦s♦♣ s♦♥ss rs ♥ ♥trs②♠♠tr ♠♦♥♦♥

tts s ♥ sst s ♣♦ss ♠♥s♠ t♦ ♥rt s♦t♦♥s ♦♥ s♣ s♣t

Page 16: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

rt♦♥s ♦♥ t ♠r♦strtr ❬❪ ♥ tt s♥s t r♠ ♣②r♠ ①t tt

s♦ s♦♠ ♥trst♥ ③r♦s♦♣ rtrsts ♦r t rst ♥ s♦♥ s♦♥ss rs

t♦ ♥♦t ♦r t rst ♦♥ s ♥t ♥ s♣ ♠♦♥♦♥ ♦♥rt♦♥s ② ❲♥

♥ ②♥ ❬❪ ♦ ③r♦s♦♣ s♦♥ss r ♥ ♦sr ♦r t ♣r♦♣t♦♥ ♥

t xy ♣♥ t ♥ s♦tr♦♣ rtt② ♦r s1 (φ) ♥ s3 (φ) ♥ str♦♥ rt♦♥t② ♥

s2 (φ) ♦r φ = 0, π/2, π, 3π/2 r s ♥ t s ♦ t xz ♣♥ ♣r♦♣t♦♥

t ♦ts ♦rrs♣♦♥♥ t♦ t s♦♥ s♦♥ss r t♥ t♦ t♠s ♦r ♥

♥♦r♠s tr♠s ♦r t ♠ tt rs δ = 5.0 t♥ t q s♣t rt♦ ♥

♣t ♦♥rt♦♥s t δ = 1.0

❲ s♣rs♦♥

♥ ts st♦♥ q♥tts ♦ ♥trst r ♥ ♥ ♥♦♥♠♥s♦♥ ♥ts rr♥

♦t② s ♦♥sr s

cT =

Ec

2(1− νc)ρc

r Ec νc ♥ ρc r t ❨♦♥s ♠♦s P♦ss♦♥s rt♦ ♥ ♥st② ♦ t s ♠tr

♥ t ss♦t rr♥ rq♥② s

fref =πcTL

s♣rs♦♥ ♦♥ Γ−X rt♦♥ ♦ t s②st♠

r s♦s t r ♣rt ♦ t s♣rs♦♥ rs Re(kn) ♥ t s ♦ ♥r♥

♠ss ♥♥ t s ♥♠r ♦t♥ rsts ♥t r ♦♠

♣①t② ♦ t r♦♦st ♦r ♦ t r♠ ♣②r♠ tt s②st♠ ♥♦r♣♦rt♥

♥♠r♦s ♥s♥t ♠♦s ♥ ♦♠♣① s♣rs♦♥ rs ♦r ♣r♦♣t ♦♥s s st

♠♦ s t ② s♥ ♥r② ♦t② rtr♦♥ s♦ tt Cgn(ω, φ).Φ > τcT

t τ = 0.5% rt♥ ♣r♦♣t s r ♣rs♥t ♥ r t s ♣♦ss

t♦ t t s②st♠ rq♥② ♥ ♣s t t rst ♦♥ t♥ ♥ ♦

t rr♥ rq♥② t s♦♥ t♥ ♥ ♥rr♦ ♥♣ ♦♥ ♥

♥t r♦♥ ③ t st ♦♥ s ♣rs♥t t♥ ♥ t♥r

♠ s ♠♦s A0 So ♥ ♦sr ♥ r② ♦ rq♥② ♥ ♦rr

Page 17: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

s♣♦♥♥ r♦♣ ♦ts r♠ s s♦♥ ♥ r r ♥ ♣ strtr ♥

♣rtr ♣r♦♣t rtrsts ② ttrt t♦ t ♥s ①t ♦r ♥

♦sr t♥ ♥ ♦ t rr♥ rq♥②

s♣rs♦♥ ♦ t s②st♠ ♥ t ♦ ♠♥s♦♥ s♣

♣r♦♣♦s ♦♠♣tt♦♥ ♠t♦ ♦s s t♦ ♦♠♣t ♠t ♠♦ s ♣r♦♣

t♦♥ ♥ t ♦♠♣t ♠♥s♦♥ ks♣ ♦ t rst r♦♥ ③♦♥ ♣r♦♣♦s

♠t♦♦♦② s s ♦♥ t ♦♠♣tt♦♥ ♦ rq♥②♣♥♥t ♦♠♣① ♥♠rs

♦ t♦r♠ s ①♣♥ ♥ t s ♦ ♠♣ s②st♠s ♥ t rsts ♦t♥

♦♠ ♦♠♣① ♥trt♥ ♣s ♦t② ♥ ♥s♥t ♣rt ♦r ♦♠♣t

♥♠r ss♦t t♦ t r ♥ ♠♥r② ♣rts ♦ t ♦t♥ ♥s ♦ qt♦♥

♠♣♥ ♦r s ♥tr♦ ② ss♠♥ ♦♠♣① ♦♦ stt② t♥s♦r

s♠ ♠t♦♦♦② ♦ ♥ r③ ② ♥tr♦♥ ♥② ♥ ♦ ♥r s♦st

♠♦♥ s s s♦s ♦r ♦r ♥② ♦tr ♦♠♣① rq♥②♣♥♥t tr♠s

r strts t t②♣ rsts ♦ t ♥②ss Pr♦♣t ♥♠rs ♦ t

♠♣ s②st♠ r s♦♥ ♦r r♥t ♥s r♦♠ φ = 0 t♦ φ = 45o t st♣ ♦ 9o t

♥ ♦sr tt φ = 0 t s②♠♠tr② strt ♥ r st ①sts s

s♦♦♥ s ♦tr rt♦♥s r ♦♥sr t ♣♣rs t t♦ rs♣ t ♦t♥ rsts

t t rt ♦t♦♥ ♥t♦ t rst r♦♥ ③♦♥ s ♥ ①♣♥ ② t t tt t

♣r♦t② ♦ t ♥t ♣ttr♥ s ♦st ♥ t ♦r♥tt♦♥ s ♥♦t ♣r t♦ ♦♥ ♦ t ss

♦ t ♥t ♥ s t♦ ♠♥s♦♥ ♦♥sst♥t tr♥s♦r♠t♦♥ ♦sr ♥

♣ strtr s♦ ♣♥s ♦♥t♦ t ♣r♦♣t ♥s r♦r t♦ t t ♥♣

♦ t ♣r♦ s②st♠ ♥ ♥t♦r ♦ ♠♥♠ ♥s♥ rt♦ ♦ t ♦♠♣t s

♦r ♦♥sr rq♥② ♥ s ♥ s

Ind(ω, φ) = minn

Real(λn)

|(λn)|

r s♦s t ♣♦t ♦ ts ♥t♦r ♥ t ♦ ♦♠♥ ♦t♦♥ ♦ t

♥ ♣s ♥ ♦sr r② ♥ ♥t tt s♣ rtt② ♥ ①sts t rt♥

rq♥s s t ♥ ♣s r ♥♦t ①s②♠♠tr ♥ ♥ ♦t t♥ s♣

♥s ①♠♠ ♥s♥ s ♦sr ♦♥ t rt♦♥s ♦ t r♠ ♣②r♠

rs ♦ ♥t l ♦r ♦ rq♥② r♥s ♦ ③ t♥ ♥ ③ t

Page 18: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♠①♠♠ ♥s♥ s♦s ♥ s♦tr♦♣ rtt② ♦ ③ t ♠①♠♠

rtt② s ♥ ♦sr ♦♥ t ①s ♦ t s♠♥ts l ♦ t ①t tt

❱ ❯

r♠ ♣②r♠ tt sr ♥ ts ♦r s s♦♥ t ♦♦♥ r

trsts

tt s ♥ ♥♣♥ ①t ♦r t s ♦ t t P♦ss♦♥s

rt♦ ♣♥♥ ♦r t ♦♠tr② ♣r♠trs ♦ t r ♦♥rt♦♥s Pt

rs t♥ t♦ rs t ①tt② ♦ t ♦♥②♦♠ ♦t♦♣♥ P♦ss♦♥s

rt♦ s ♣♦st ♦r t ♦♥rt♦♥s ♦♥sr

♥♣♥ ♥① st♥ss ❨♦♥s ♠♦s Ex s r ♦♠♣r t♦ t tr♥s

rs s r♠ ♣②r♠ tt s ♣rs♠t ♦♥②♦♠ t

t ♦r♥t tr♦ t t♥ss tr♦r ①♣♥♥ ts rtr ♣r

♠♥ ♦r s♠r tr♥ s ♦sr s♦ ♦r t sr ♠♦s

t♦ t s ♣♦ss t♦ ♥t② ♦♠♥t♦♥ ♦ ♥tr♥ ♥ ♥ r s♣t

rt♦ δ tt s t♦ Gxy = Gxz stt♦♥

❩r♦s♦♣ s♦♥ss rs ♥ ♦sr ♦r t ♣r♦♣t♦♥ ♥ t xz ♣♥

♦r t rst ♥ s♦♥ rs rs♣t② sst♥ ♣♦ss rt♦♥s ♦r t

t♦r r s♦t♦♥s ♦ rt s♥ ts tt s ♣t♦r♠ ♦ ③r♦rtr

♦r t s♦♥ss rs s ♥ ♥t ♥ t xy ♣♥

❲♥ ♦♥sr♥ ♠♥s♦♥ ♣r♦♣t♦♥ t♥ ♥t♦ ♦♥t t t

s ♦ t ♠r♦strtr ♥♦t ♥ ♦♥♥ t♦ t ♦♥ ♥t ♣♣r♦①♠

t♦♥ ♦ ♣♦♥ts t r♠ tt s♦s ♦♠♣① ♣ttr♥ ♥ ♥ t xy

♣♥ ♥ s♠ s ♦ ②strt ♠♣♥ s ♦♥sr ❯s♥ ♥ ♥s♥

♥① rt ♦r ts tt t s ♣♦ss t♦ ♥t② ♥s♥ rtt② ♣t

tr♥s t rt♦♥t② ♣♥♥ ♦ t ♠t♠♦ rtrsts ♦ t r♠

①t ♣②r♠ tt

Page 19: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♥♦♠♥ts

s ♦r s ♥ ♣rt② s♣♣♦rt ② r♥t♥ ♦r P ♦s ② t ♣♥

♦t② ♦r Pr♦♠♦t♦♥ ♦ ♥

❬❪ t ❲② P②r♠ tt trss strtrs t ♦♦ trsss t

rs ♥ ♥ ♥♥r♥ ♦❭♥♦④♦⑥④

♠s⑥

❬❪ t ❲② t♥♠ ♦② tt trss strtrs trs ♠♣

s♥ ♦❭♥♦④♦⑥④♠ts

❬❪ ❲② t♥t♦♥ ♣r♦ r ♠ts P♦s♦♣ r♥st♦♥s ♦ t ♦②

♦t② t♠t P②s ♥ ♥♥r♥ ♥s ♦

❭♥♦④♦⑥④rst⑥

❬❪ P♥ ❱ s♣♥ ❲② ♦♣s ♠♥s♠ ♠♣s ♦r

♦♦ ♣②r♠ tt Pr♦♥s ♦ t ♦② ♦t② t♠t P②s ♥

♥♥r♥ ♥ ♦❭♥♦④♦⑥④rs♣⑥

❬❪ rs♦♥ rs♦♥ ①t trs Pr♦♥s ♦ t ♥sttt♦♥ ♦ ♥

♥♥rs Prt ♦r♥ ♦ r♦s♣ ♥♥r♥

❬❪ ♦♥ ③③♥ ♥②ss ♦ ♥♣♥ ♣r♦♣t♦♥ ♥ ①♦♥ ♥ r♥tr♥t

tts ♦♥ ❱rt

❬❪ ♣♦♥ ③③♥ ♠r ♥ ①♣r♠♥t ♥②ss ♦ tt ♦♠♣♥ ♦

r rss ♦r r♦s ♦r♥ ♦ ♥s ♦ trs ♥ trtrs

❬❪ ♣♦♥ r♣ ③③♥ ❲ ♣r♦♣t♦♥ ♥ ①t ttrr ♦♥②

♦♠s ♦r♥ ♦ ❱rt♦♥ ♥ ♦sts

❬❪ rt♥ ②rr♥r ♠t r♣ P♦ttr ③③♥ ①r

♣rs♠t ♥♦① ♦♥♣t P②s tts ♦

❬❪ tt♥ P r♦ ♥r♦ ③③♥ ♣♦♥ ♦♠♣♦st r str

trs ♦r ♠♦r♣♥ r♦s ♠r ♥②ss ♥ ♦♣♠♥t ♦ ♠♥tr♥ ♣r♦ss

Page 20: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♦♠♣♦sts Prt ♥♥r♥

❬❪ r♠ ❲♠s tt ♥s ♦♥ ♦ ①t ♥t♦r ♣♦②♠rs

t r♦♠ ①❬❪r♥ ♥ ♦s ♦r ♠t♦♥ ♦

❭♥♦④♦⑥④⑥

❬❪ ❱ ♦ ♦ ♦③♦ ❩♥ ♥ts

♠♥ ♥ ♥ ♦ P♦ss♦♥s t♦ ♦r r♦♥ ♥♦t ts ♥

♦❭♥♦④♦⑥④s♥⑥

❬❪ ❱ ♦ ♦③♦ ❩♥ ♥ts ã♦ ♠♥

♦♥ t ①t tr♥st♦♥ ♦r r♦♥ ♥♥♦t sts P②s

♦❭♥♦④♦⑥④P②s⑥

❬❪ ♦♠ t♦ ♦♣♠♥t ♦ ② s♥ ❯trt ♦r trtrs

♥tr♥t♦♥ ♦r♥ rs

❬❪ t♦ r♣ r♠ ♦♠♣♦st ①t ♦♥②♦♠ ♥ t ♥tr♥t♦♥

♦♥r♥ ♦♥ ♦♠♣♦st trtrs

❬❪ t♦ ♥s r♣ r r♠ ♦r♣♥ ❲♥♦① ♦♥♣t ♦r♥ ♦

♥t♥t tr ②st♠s ♥ trtrs ♦❭♥♦④♦⑥④

❳⑥

❬❪ P ❲♦ ♠♥ P♦♥♦♥s ♠r ❯♥rst② Prss ♠r ❯

❬❪ ♦r♥rt rt P ♦r♠♥ ♦♠♦é♥ést♦♥ ♥ ♠é♥q s ♠tér①

♥ r♦♣ t

❬❪ r ♦♥sttt ♠♦♥ ♦ ♣③♦tr ♣♦②♠r ♦♠♣♦sts t tr

♦❭♥♦④♦⑥④t♠t

❬❪ ② ❲ ♣r♦♣t♦♥ ♥ ②r ♥s♦tr♦♣ ♠ t ♣♣t♦♥s t♦ ♦♠♣♦sts

♦rt ♦♥ sr ♥ ❱

❬❪ ❲♥ ②♥ ①st♥ ♦ ①tr♦r♥r② ③r♦rtr s♦♥ss r ♥ ♥s♦tr♦♣

st ♠ ♦r♥ ♦ t ♦st ♦t② ♦ ♠r

♦❭♥♦④♦⑥④⑥

❬❪ r ♦♥s ♦ ❲s ♦♠♦♥③t♦♥ ♥ ♣tr s②♠♣t♦t ♥②ss ♦r

♥ té♠tqs Prs t ♣♣qés

❬❪ ♦ r♦t ♥ s r♦♣ ♥ ♥r② ♦ts ♥t

Page 21: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

♠♥ts ♦r♥ ♦ ♦♥ ♥ ❱rt♦♥ ❳ ♦

❭♥♦④♦⑥④④s⑥⑥

❬❪ ♥ ♦ t♠♦ ♣r♦♣t♦♥ ♥ s♦♥ ♥ strtrs tr♦ ♥t

♠♥ts r♦♣♥ ♦r♥ ♦ ♥s ♦s

♦❭♥♦④♦⑥④④r♦♠s♦⑥⑥

❬❪ ♦♦♥ ♦ ③q ❲ ♠♦t♦♥ ♥ t♥ strtrs ♦r♥ ♦ ♦♥

♥ ❱rt♦♥ ❳ ♦❭♥♦④♦⑥④④s

⑥⑥

❬❪ ♦t ss ③③♥ ♦ ♦qt♦ ♦♠♣♦st♦♥ ♦ t st♦

②♥♠ qt♦♥s ♣♣t♦♥ t♦ ♠♥s♦♥ s s♣rs♦♥ ♦♠♣tt♦♥ ♦ ♠♣

♠♥ s②st♠ ♥tr♥t♦♥ ♦r♥ ♦ ♦s ♥ trtrs

❬❪ ♦t ♥r ♦ ❲ ♦t♦♥ ♣t♠③t♦♥ ♥ Pr♦② strt

♥t P③♦♦♠♣♦st ♠ trtrs ♦r♥ ♦ ♥t t ②st ♥ trt

❬❪ r ♦♠♣tt♦♥ ♦ ♣r♦♣t s ♥ r r s♥ ♥t ♠♥t t♥q

♦r♥ ♦ ♦♥ ♥ ❱rt♦♥

❬❪ ❲ ②s♥ör ör♣rs♥r r♥♥ ③r r♥♥ ♦♥ ♥rt♥ ♥

♥t♥stät♥ ❲ss♥st ❱rssst tttrt

❬❪ rt♦t ssrr ❨ r♥ ♠♣♥ ♥②ss ♦ ♦♠♣♦st ♠

trs ♥ strtrs ♦♠♣♦st trtrs ♦

❭♥♦④♦⑥④♦♠♣strt⑥

❬❪ ♦q ♦r♥s♥ ❨♥ P srs s♦t♦♥ ♦ rs ♥

♣r♦♠s t ♠♣t② rstrt r♥♦ ♠t♦s ♠

❬❪ ♥ ärt♥r ♦♥ ♥s②♠♠tr s♣rs s②st♠s ♦ ♥r qt♦♥s t P

tr ♥rt♦♥ ♦♠♣tr ②st♠s ❳

❬❪ r♣ P P♥②♦t♦ ♦♠♥s♦♥ ♠r ♥ ①♣r♠♥t ♥① ♦♥ ♦♥ ♥

♣♥ ①t ♦♥②♦♠s ♦r♥ ♦ tr♥ ♥②ss ♦r ♥♥r♥ s♥

♦❭♥♦④♦⑥④⑥

❬❪ s♦♥ s② ♥s ♦ r♠♥s♦♥ r trs Pr♦

♥s ♦ t ♦② ♦t② ♦ ♦♥♦♥ t♠t ♥ P②s ♥s

♦❭♥♦④♦⑥④rs♣⑥

Page 22: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r ❱ ♣ t ♣②r♠ r♠ ♦r t ts ♥♦♥♠♥s♦♥ ♦♠tr②

♣r♠trs ❱ t α = 1, β = 0.05, δ = 6, θ = 20o

r ♥r ♣r♦ s

Page 23: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r ②♦t ♦ t ♠♣ r♠ tt ♥t ♦♥sr ♦r t

♣r♦♣t♦♥ st②

r ❯♥r♥ ♥ r♥ ♠s ss

Page 24: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

0 10 20 30 40 50 60 70 80−0.9

−0.8

−0.7

−0.6

−0.5

−0.4

−0.3

−0.2

−0.1

0

0.1

θ [o]

ν xy

δ = 1.0

δ = 3.0

δ = 5.0

0 10 20 30 40 50 60 70 800.2

0.25

0.3

0.35

0.4

0.45

0.5

θ [o]

ν xz

δ = 1.0

δ = 3.0

δ = 5.0

r strt♦♥ ♦ t P♦ss♦♥s rt♦s νxy ♥ νxz rss t ♥ θ ♦r

r♥t δ ♣r♠trs ♥ α = 1

Page 25: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

20 30 40 50 600

0.5

1

1.5

2

2.5

3

3.5

4

4.5

θ [o]

2 4 6 80

50

100

150

200

θ

Ex/E

c X 103, δ = 1.0

Ez/E

c X 103, δ = 1.0

Ex/E

c X 103, δ = 3.0

Ez/E

c X 103, δ = 3.0

30 40 50 60 70 800

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

θ [o]

2 4 6 8 100

10

20

30

40

θG

xy/G

c X 103, δ = 1.0

Gxz

/Gc X 103, δ = 1.0

Gxy

/Gc X 103, δ = 3.0

Gxz

/Gc X 103, δ = 3.0

r ♦♥♠♥s♦♥ ♥♣♥ ♥ tr♥srs ❨♦♥s ♠♦s rss t ♥tr♥

♥ θ ♦r r♥t s♣t rt♦s δ ♠r ♣r♠tr rs ♦r ♥♦♥♠♥s♦♥

♥♣♥ sr ♥ tr♥srs ♠♦s ♦r t♦♥s α = 1

Page 26: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

0.5

1

1.5

30

210

60

240

90

270

120

300

150

330

180 0

θ = 20o

s1(φ)

s2(φ)

s3(φ)

δ = 1.0

θ = 20o

s1(φ)

s2(φ)

s3(φ)

δ = 5.0

r ♦♥ss r ♥ t xz ♣♥ ♦r α = 1, θ = 20o

Page 27: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

0.1 0.2 0.3

θ = 20o

s1(φ)

s2(φ)

s3(φ)

δ = 1.0

θ = 20o

s1(φ)

s2(φ)

s3(φ)

δ = 5.0

r ♦♥ss rs ♥ t xy ♣♥ ♦r α = 1.0, θ = 20o

Page 28: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

0 0.2 0.4 0.6 0.8 10

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Real part of reduced wave number

Re

du

ce

d f

req

ue

ncy

r s♣rs♦♥ rs ♦ ♠♦s ♦ t st s②st♠ ♠♥r② ♣rt ♦ λn(ω)

♦r r ♣rt ♦ kn(ω)

0 0.2 0.4 0.6 0.8 10

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Real part of reduced wave number

Re

du

ce

d f

req

ue

ncy

r s♣rs♦♥ rs ♦ ♣r♦♣t ♠♦s ♦ t st s②st♠ ♠♥r② ♣rt

♦ λn(ω) ♦r r ♣rt ♦ kn(ω)

Page 29: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

0 0.02 0.04 0.06 0.08 0.1 0.12 0.140

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Real part of reduced group velocity

Re

du

ce

d f

req

ue

ncy

r s♣rs♦♥ rs ♦ ♣r♦♣t ♠♦s ♦ t st s②st♠ ♠♥r② ♣rt

♦ λn(ω) ♦r r ♣rt ♦ kn(ω)

0 0.2 0.4 0.6 0.8 10

0.02

0.04

0.06

0.08

0.1

Reduced fre

quency

φ=0

0 0.5 1 1.50

0.02

0.04

0.06

0.08

0.1

φ=π/20

0 0.5 1 1.50

0.02

0.04

0.06

0.08

0.1

φ=π/10

0 0.5 1 1.50

0.02

0.04

0.06

0.08

0.1

Reduced fre

quency

Propagative part of reduced wave number

φ=3π/20

0 0.5 1 1.50

0.02

0.04

0.06

0.08

0.1

Propagative part of reduced wave number

φ=π/5

0 0.5 1 1.50

0.02

0.04

0.06

0.08

0.1

Propagative part of reduced wave number

φ=π/4

r Pr♦♣t ♥♠rs ♦ ♠♣ s②st♠ Im(λn(ω) ♦r r♥t ♥s

Page 30: Kirigami Auxetic Pyramidal Core: Mechanical Properties and

r rtt② s♥ t ♥s♥ ♥① strt t ♥t