MIL-C-7438 Core Material Aluminum for Sandwich Construction Rev G

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M L-C- 7438G

19 J une 1985

SUPERSEDI NG

MLITARY SPECI FI CATI ON

CORE MATERI AL , ALUMNUM FOR SANDWCH

Thi s speci f i cat i on i s approved for use by

and Agenci es of the Department of Defense.

M L-C-7438F

13 March 1972

CONSTRUCTION

al l Departments

1. SCOPE

1. 1 ~. Thi s speci f i cat i on covers treated al umnum core mat eri al f or

structural sandw ch constructi on.

I .2 Cl assi f i cat i on. Al umnum core mater i al for sandw ch construct i on

shal 1 be furni shed i n the fo( l ow ng grades, as speci f i ed (see 6.2.1 and 6.4) :

Grade

For exposure up

; For exposure up

2. APPLI CABLE DOCUMENTS

2. 1 Government documents

Descri pti on

to 350F (see 3. 2. 1. 1).

to 430F (see 3. 2. 1. 2).

2.1. 1 Speci f i cat i ons and standards~. Unl ess otherw se speci f i ed, the

fol l ow ncj speci f i cat ions and standards of the i ssue l i sted i n that i ssue of

the t)epa~tment of Defense I ndex of Speci fi cati ons and Standards (DoDI SS)

speci f i ed i n the sol i ci t at ion forma par t of thi s speci f i cat ion to the extent

speci f i ed herei n.

SPECI FI CATI ONS

FEOERAL

QQ- A- 25014 - Al umnum Al I oy 2024, Pl ate and Sheet.

QQ- A- 25015 - Al um num Al l oy Al cl ad 2024, Pl ate and Sheet.

UU-P-268

Paper, Kraf t, MraPPi n9.

Benefi ci al comments (recommendati ons, addi ti ons, del eti ons) and any perti nent dat

whi ch may be of use i n i mprovi ng thi s document shoul d be addressed to: Systems

Engi neeri ng and Standardi zati on Department (Code 93) , Naval Ai r Engi neeri ng Cente

Lakehurst, NJ 08733-5100, by usi ng the sel f - addressed Standardi zati on Oocument

Improvement Proposal (00 Form 1426) appeari ng at the end of thi s document or by

netter.

FSC 5680

DI STRI BUTI ON STATEMENT A, Approved for publ i c rel ease; di stri buti on i s unl i mted.


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ML-C-7438G

SPECI FI CATIONS

FEDERAL (conti nued)

PPP-B-576

PPP-B-585

PPP-B-591

PPP-B-636

PPP-B-640

MLI TARY

ML-P-116

M L-C=5541

M L-H-6088

M L-A-81596

STANDAROS

FEDERAL

FED-STD-595

MLI TARY

M L-STD-105

M L-STD- l 29

M L-STD-401

Box, Hood, Cl eated, Veneer, Paper Overl ai d.

Boxes, Wood, Hi rebound.

Boxes, Shi ppi ng, Fi berboard, Wood-Cl eated.

Boxes, Shi ppi ng, Fi berboard.

Box, Fi berboard, Corrugated, Tri pl e-Wal 1.

Preservati on, Methods of .

Chemcal Conversi on Coati ngs on Al umnum Al l oys

Heat Treatment of Al umnum Al 10YS.

Al umnum Foi 1 for Sandw ch Constructi on.

Col ors.

Sampi l ng Procedures and Tabl es for I nspecti on by

Attri butes.

Marki ng for Shi pment and Storage.

Sandw ch Constructi on and Core Materi al s,

General Test Methods.

(Copi es of speci f i cati ons, standards, handbooks,

requi red by contractors i n connecti on w th speci f i c

shoul d be obtai ned from the acqui si t i on acti vi ty or

contracti ng of fi cer. )

draw ngs, and publ i cati ons

acqui si ti on functi ons

as di rected by the

2,2 Other publ i cat ions. The fol l ow ng documents form a part of thi s

speci fi cati on to the extent speci fi ed herei n.

The i ssues of the documents

whi ch are i ndi cated as DoO adopted shal l be the i ssue l i sted i n the current

DoOI SS and suppl ement thereto, i f appi i cabl e.

AMERI CAN SOCI ETY

ASTM B 117 -

ASTM C 366 -

ASTM D 3951 -

FOR TESTI NG AND MATERI ALS (ASTM

Sal t Spray (Fog) Testi ng.

Measurement of Thi ckness of Sandw ch Cores

Commerci al Packagi ng, Practi ce for.

(Appl i cati on for copi es shoul d be addressed to the Ameri can Soci ety for

Testi ng and Materi al s, 1916 Race Street, Phi l adel phi a, PA 19103. )

(I ndustry associ ati on speci fi cati ons and standards are general l y avai Iabl e

for reference from 1i brari es, They are al so di stri buted among techni cal

groups and usi ng Federal agenci es. )

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ml L-L,- 14.SMb

2.3 Order or precedence. In the event of a conf l i ct between the text of

thi s speci f i cat ion and the references ci ted herei n, the text of thi s

speci f i cati on shal 1 take precedence.

3. REQUI REMENTS

3. 1 Fi r st arti cl e.

14henspeci f i ed, sampl es shal l

art icl e i nspect i on (see 4. 5 and 6. 3) .

3. 2 Material s. The material s compris ing the core

appl i cabl e speci fi cati ons and as speci fi ed herei n.

be subj ected to f i rst

shal 1 conform to the

3.2.1 Metal . The core shal l be fabr i cated f rom alumnum al l oy foi l

conformng to M L-A-81596.

3. 2. 1. 1 Grade B. Grade B core shal l be of Al l oy 5052 or Al l oy 5056 f oi l ,

as speci f i ed (see 3. 2. 4 and 6. 2.1) .

* 3. 2. 1. 2 Grade C. Grade C core shal I be of Al l oy 2024-T3 or Al l oy 2024-T81

foi l (see 3. 2. 4 and 6.2.1) . Al l oy 2024-T3 shal i be subsequentl y preci pi tat i on

hardened to the - T81 condi ti on accordi ng to the recommended ti me- temperature

cycl e speci f i ed i n M L-H-6088, ei ther prior to bondi ng i nto a sandw ch

assembl y or duri ng the bondi ng cycl e of a sandw ch assembl y. When speci fi ed

i n the -T3 temper, the sampl es sel ected for test i ng shal 1 be converted to the

-T81 condi ti on, except for the materi al for del amnati on strength testi ng.

3.2. 2 Metal Fi ni sh.

The core shal 1 be formed from chemcal l y treated or

coated foi 1 for protecti on agai nst corrosi on.

The f oi l shal l be gi ven a

chemcal conversi on coati ng i n accordance w th M L-C-5541, Cl ass 1A or

equi val ent.

3. 2. 3 Bondi ng materi al .

The adhesi ve used to bond the al umnum foi I to

form the cel l s of the core shal 1 be of such qual i ty that the resul tant core

w l l meet the requi rements speci fi ed herei n.

3. 2. 4 Trade name and code number. The manufacturer shal l designate each

core materi al combi nati on by a trade name and code number whi ch shal 1 be used

to i denti fy the core (see 6- . 2.1) .

The code number shal 1 consi st of the

fol l ow ng:

a.

b.

c.

d.

e.

f .

9.

Desi gnated densi ty.

Cel l si ze i n f ract i ons of an i nch.

Nomnal foi 1 thi ckness i n ten-thousandths of an i nch.

P for per forat i on, i f so speci f i ed ( see 3.3.2) . For non-

perforati on, no codi ng requi red.

Al 10Y (standard desi gnati on). I f appl i cabl e, temper requi red

(see 3. 2. 1. 2).

For hexagonal core cel 1 wal 1s, C for corrugated i f so

speci fi ed. For expanded, no codi ng requi red.

S for speci al core cel I conf i gurat i ons, i f other than hexa-

gonal .

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Exampl e: Grade B

fabr icated w th a

nonperf orated and

fol l ows:

M L-C- 743BG

mater ial w th a densi ty of 4.5 pounds per cubi c foot ,

l / 8- i nch cel l si ze, and 0. 0010 i nch nomnal thi ckness,

usi ng corrugated untreated Al l oy 5052 shal l be coded as

Trade name - 4. 5- l / B- 10(5052)C

Exampl e: Grade C mater ial w th a densi ty of 5.0 pounds per cubi c foot ,

fabr icated w th a I / B- i nch cel l si ze, and 0.0015 i nch nomnal thi ckness,

nonperforated and capabl e of bei ng expanded, usi ng treated Al l oy 2024-T3 shal 1

be coded as fol l ows:

Trade name - 5.O- l / 8- 15(2024-T3)

I f the core cel 1 conf i gurat i on i s other than hexagonal , such as rei nforced

hexagonal , doubl e corrugated, or staggered hexagonal , then the core shal I be

coded as fol l ows:

Trade name - 4. 5- l / B- 10(5056)S

3. 3 Fabri cati on.

3. 3. 1 Confi gurati on.

The core mater ial shal l consi st of thi n al umnum

sheets bonded together to form cel l s approxi matel y of uni form shapes, usual l Y

hexagonal i n shape. The cores shal l be made ei ther by assembl i ng corrugated

r ibbons or by str ip-bondi ng f l at r i bbons and then expandi ng the core cel 1s to

proper shape. I f the core materi al i s purchased i n the unexpanded condi t i on,

i t shal l be capabl e of meet i ng the requi rements of thi s speci f i cat i on after

proper expansi on to the ful l cel 1 confi gurati on and proper densi ty.

3.3.2 Per forat ion. Unl ess otherwse speci f i ed (see 6.2.1) , the al umnum

foi 1 shal 1 be non-perforated. Nhen perforati on i s speci f i ed, the perforati ons

shal I be of such si ze and l ocat i on that al l cel l s are vented at l east every

1/ 4 i nch i n thi ckness di mensi on.

3. 3. 3 @ -l J .

The core shal 1 be furni shed as pi eces, unexpanded bl ocks or

sl i ces, or expanded panel s as speci f i ed by the acqui r i ng acti vi ty.

The

di mensi ons and tol erances for the pi eces, bl ocks, sl i ces or panel s shal l be as

speci fi ed by the acqui ri ng acti vi ty.

3. 4 Physi cal properti es.

Physi cal propert ies and tol erances shal l be i n

accordance w th Tabl e 1,

3.4.1 Foi l thi ckness.

The core f oi l thi ckness shal l be w t hi n the l i m ts

of desi gnated val ue speci f i ed i n Tabl e I I .

3. 5 Compressi ve and shear strength Properti es of hexagonal confi gurati on

core. Core f l atw se compressi ve strength and shear strength (associ ated w th

shear di stor ti on i n the LT and NT pl anes, see Fi gure 2) for the nomnal

densi ty of the core shal l conform to the requi rements l i sted i n Tabl e 111 as

appl icabl e for the basi s metal and test condi t i ons.

Compressi ve strength and

shear st rength of any speci men shal l be not l ess than the val ue speci f i ed i n

the appl i cabl e tabl es (see Tabl es IV - X) when tested i n accordance w th the

appl i cabl e test procedure (see 4.7.5 - 4.7.8) . When shear st rength i s

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M L-C-7438G

determned by usi ng the beam fl exural shear test,

sandw ch shal l be Al l oy 2024-13 or 2024-T81 bare.

c1ad, conformng to @A-250J 5.

the faci ngs of the core

conformng to @Q-A-25014, or

3.6 Del amnati on strength. The core shal 1 have a del amnati on strength or

node bond strength capabl e of w thstandi ng not l ess than the ul ti mate tensi l e

l oad speci f i ed in Tabl e XI or Tabl e XI I , as appl i cabl e, for the Grades and

test condi t i ons. I n case of par ti al del amnat i on at not l ess than the

speci f i ed ul t i mate tensi l e strength l oad for a speci f i ed test condi t i on, the

del amnat ion areas shal 1 be l ess than 10 percent of the total bond area i n the

stress sect i on of the core (see 4.7.9) .

3. 7 Corrosi on resi stance

propert ies. Thematerial shal l be treated so as

to be capabi e of protect i ng the base metai when subj ected to the sal t spray

test speci f i ed i n 4.7.10. At the end of 30 days exposure, the core shai l not

show a l oss of wei ght greater than 125 m I l i grams per square foot of exposed

foi l area.

3. 8 Mechani cal properti es of speci al core confi gurati on. The mechani cal

properti es of speci al core confi gurati on or hexagonal confi gurati on materi al ,

not speci f i ed herei n, shal l be speci f i ed i n the contract or purchase order , or

covered by appl i cabl e draw ngs (see 6. 2. 1).

3. 9 Col or code i denti f i cati on.

3. 9. 1 Grade B

Each bl ock or sl i ce of Grade B core shal l be i dent i f i ed on

the edges - stri pes, about 2 i nches wde, whi ch shal l match Col or No.

11105 or 21105 of FED-STD-595 and 1/ 2 i nch w de stri pes appl i ed at i nterval s

of not l ess than 2 f eet . The col or of t he st ri pes f or t he core al l oy materi al

and desi gnated densi ty range shal 1 be i n accordance w th Tabl e XI I I . The

col or shal I be produced by addi ng a dye to an adhesi ve whi ch i s compati bl e

w th the core. St ri pes shal l be pai nted or sprayed on the edges of core

bl ocks or sl i ces. The permanent dye shal 1 retai n i ts col or through the curing

cycl e and shal l be non- corrosi ve.

The dye shal 1 not adversel y affect the

curing nor the strength of the adhesi ve used for construct i on of the core nor

the adhesi ve used w th the core i n the fabri cati on of sandw ch components.

3. 9. 2 Grade C. Each bl ock or sl i ce of Grade C core shal l be i dent i f i ed on

the edges by two st ri pes, about 2 inches w de w th a nar row st ri pe about 1/2

i nch w de between the w de st ri pes. The st ri pes shal l be appl i ed at i nterval s

of not l ess than two feet . The w de st ri pes shal l be yel l ow and shal l mat ch

Col or No. 13655 or 23655 of FED-STD-595.

The col or of the stri pes f or the

desi gnated nomnal densi ty shal l be i n accordance w th Tabl e XI V. Other

requi rements for col or shal l be as detai l ed i n 3. 9. 1.

3. 10 Workmanshi p. The core materi al shal 1 be free from defects that woul d

affect adversel y the propert ies of the end i tem The materi al shal 1 be cl ean

and free fromgrease, oi l , tr im scraps, and i mpuri t i es.

The foi l edges of the

core materi al shal 1 be free from notches, crush l i nes and rol l ed metal

Expanded core S1i ces havi ng doubl e foi I S (two ri bbons bonded together causi ng

uneven expansi on i n the L di rect i on) shal l be acceptabl e i f the doubl e foi 1s

are not more frequent than one i n ei ght i nches i n the transverse (W di rect i on

(see 4. 6. 2. i ) .

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M L-C-7438G

3. 10. 1 Vi sual i mperfect i ons. Vi sual i mperfect i ons shal l not exceed the

val ues speci f i ed In Tabl e XV for the specl f l ed cel l si ze (see 4.6.2.1,1) .

msmatched nodes for corrugated

otherwse speci f i ed i n the

3.10.2 Msmatched nodes. The c/ d rat io of

core shal l not exceed 0. 25 (see 4. 6. 2. 1. 1).

4. QUALITY ASSURANCE PROVI SI ONS

4. 1 Responsi bi l i ty for i nspect i on . Unl ess

contract or purchase order, the contractor i s responsi bl e for the performance

of al l i nspecti on requi rements as speci fi ed herei n.

Except as otherw se

speci f i ed i n the contract or purchase order, the contractor may use hi s own or

any other faci I i t i es sui tabl e for the performance of the I nspect i on

requi rements speci fi ed herei n, unl ess di sapproved by the Government. The

Government reserves the right to perform any of the i nspect i ons set forth i n

the speci fi cati on where such i nspecti ons are deemed necessary to assure that

suppl i es and servi ces conform to prescri bed requi rements.

4. 2 Sampl i ng. Unl ess otherw se speci fi ed, sampl i ng pl ans and procedures

i n the determnati on of the . acceptabi l i ty of products shal l be i n accordance

w th the provi si ons set forth i n M L-STD-105.

4. 3 Q. Unl ess ot herw se speci f i ed i n t he cont ract or order ( see 6. 2. 1) ,

a l ot shal l consi st of not more than 100 cubi c f eet of mater i al of the same

desi gnated cel l si ze di mensi on, nomnal foi l thi ckness, densi ty, perforati on,

al 10Y composi tl on and core conf i gurati on desi gn, manufactured under

essenti al I y the same condi ti ons.

4. 4 Cl assi f i cat i on of i nspect i on.

herei n are cl assi f i ed as fol l ows:

a. Fi r st arti cl e i nspect i on

The I nspecti on requi rements speci f i ed

(see 4. 5).

b. Qual i ty conformance i nspecti on (see 4. 6)

. 4. 5 Fi r st ar ti cl e i nspect i on. Fi r st ar ti cl e i nspect i on shal l consi st of

al l i nspect ion procedures of thi s speci f i cat ion (see 4.6 and 4.7) . The

responsi bi 1i ty for the performance of the f i rst art i cl e i nspect ion shal I be as

speci f i ed by the acqui r ing act i vi ty (see 6.2. 1 and 6. 3) .

4. 5. 1 Test sampl es. The f i r st ar ti cl e test sampl es shal l consi st of

randomy sel ected mater ial cut to a thi ckness of 0.625 f 0.010 i nch for Grade

8 or of 0. 500 f 0. 010 i nch f or Grade C.

In

addi ti on, suffi ci ent materi al for

the pl ate shear tests or sandw ch speci mens for f l exural tests shal 1 be

provi ded for a mni mum of 5 speci mens for each appl i cabl e di recti on and

temperature determnati on. Fi rst arti cl e sampl es (of desi gnated densi ty, cel l

si ze di mensi on, nomnal foi l thi ckness, al l oy composi t i on, f i ni sh, core cel l

confi gurati on) whi ch are sel ected shal I have been manufactured usi ng the same

producti on processes, procedures and equi pment whi ch w l l be used i n fi l l i ng

the contract.

4.5.2 Cer ti f i ed statement . Whether or not a f i r st ar ti cl e sampl e i s

requi red (see 4. 5. 3) , the contractor shal 1 suppl y a certi f i ed statement of

composi ti on and pri or tests whi ch shows the materi al furni shed compl i es w th

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the requi remen

M L-C- 7438G

s of thi s speci f i cat i on. The statement shal l al so incl ude the

manufacturer s trade name and code number for the materi al and the propri etary

name of the bondi ng materi al used (see 6. 3).

4.5.3 Pr ior approval . If a contractor has previ ousl y del i vered materi al i n

accordance w th the requi rements of thi s speci f i cati on and hi s product has been

found to be sat i sfactory, the requi rements for f i rst arti cl e i nspect ion for

that product, i n connect i on w th any subsequent contract or order for that

product, may be wai ved at the di scret i on of the acqui r i ng act i vi ty (see

6.2.1 and 6.3) . The approval of Fi r st Ar ti cl e samples or the wai vi ng of the

Fi rst Ar ti cl e i nspect i on shal l not rel i eve the cont ractor of hi s obl i gat i on to

ful f i l l al l other requi rements of the speci f i cat i ons and contract.

4. 5. 4 Further producti on. Any producti on of core mater

contractor pri or to approval of the acqui r ing act i vi ty shal

contractor s ri sk.

4. 6

Qual i ty conformance i nspecti on.

al by the

be at the

4. 6. 1 Sampl i nq. Sampl es shal I be taken at random from each i nspecti on

l ot. Fai l ure of any speci men to meet the requi rements of thi s speci f i cat i on

shal l const i tute cause for rej ect i on of the l ot represented (see 4.8) . The

contractor shal l furni sh al l sampl es and shal l be responsi bl e for

accompl i shi ng the requi red tests.

4.6. 1.1 Vi sual and di mensi onal examnati on. Sampl es shal l be sel ected i n

accordance w th M L-STD-105, I nspecti on Level 11.

Acceptabl e Qual i ty Level 2. 5

percent defecti ve for vi sual and di mensi onal examnati on (see 4. 6. 2. 1).

4. 6. 1.2 Physi cal and mechani cal propert ies. Suff i ci ent materi al shal l be

sel ected to conduct the tests detai l ed i n Tabl e XVI appl i cabl e for the Grade

of core.

4. 6. 1. 3 Corrosi on resi stance properti es.

Fi ve (5) test speci mens shal l be

sel ected to conduct the test detai l ed i n 4.7. 10 ( see Tabl e XVI ) . I n l i eu of

sampl I ng each i nspecti on l ot, the contractor shal l be permtted once each week

to sel ect a mni mum of 5 random speci mens from hi s producti on l i ne for

determnati on of corrosi on resi stance properti es.

4.6.2 Tests.

The qual i ty conformance tests shal l consi st of examnati on

as speci f i ~ 4. 6. 2. I and i n Tabl e XVI.

The tests shal 1 be i n conformance

w th the appl icabl e requi rements of Sect i on 3, except as noted. In addi t i on.

the materi al shal l be subj ected to any other tests speci f i ed herei n whi ch the

acqui ri ng acti vi ty consi ders necessary to determne conformance w th thi s

speci f i cati on.

4. 6. 2. 1 Examnati on. The materi al ,

sel ected i n accordance w th 4. 6. I . 1,

shal l be examned to determne compl i ance w th the requi rements of thi s

speci fi cati on for confi gurati on, perforati on,

si ze i denti f i cati on, workmanshi p

and doubl e foi l s, vi sual i mperfecti ons and msmatched nodes.

Except for the

maxi mum number of i mperfecti ons al l owed as i ndi cated i n Tabl e XV (see

4.6. 2.1. 1) , a uni t of sampl e contai ni ng one or more defects shal l be rej ected.

Fi gure 1 i I I ustrates doubl e foi l s and msmatched nodes.


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M L-C-7438G

4.6.2 .1.1 Vi sual i mperfect ions. A square foot of each

i tem shal I be examned for the number of msmatched nodes.

sel ected sampl e

l oose metal .

f l akes, unbended nodes, spl i t cel l wal l s and buckl ed cel l wal l s.

The c/ d

rat io of msmatched nodes shal l al so be determned. I f the number of

nonconformng i mperf ecti ons exceeds the acceptance number for that defect as

stated i n Tabl e XV as wei 1 as the c/ d rat io of msmatched nodes i s greater

than the speci f i ed val ue, the l ot represented by the sampl e shal l be rej ected.

4. 6. 2. 2 Physi cal , mechani cal and corrosi on resi stance properti es. The

materi al sel ected shal l be tested i n accordance w th Tabl e XVI .

4. 7 Test methods.

4. 7. 1 Core densi ty, The test speci mens may be any conveni ent si ze or

shape that can be accuratel y measured from bl ocks or 1i ces.

Specimen si ze

shal 1 be approxi matel y 4 square feet or l arger of the core materi al

Speci mens shal I be wei ghed to an accuracy of at l east I percent . Length and

w dth di mensi ons shal l be measured to the nearest 0. 01 i nch.

Thi ckness of

sl i ces shal l be measured to the nearest O.001 i nch by the use of a di al gage

whi ch appl i es 10 pounds pressure on a 1. 5 i nch di ameter area.

The core

densi ty shal l be cal cul ated by di vi di ng the wei ght of the pi ece i n pounds by

the vol ume i n cubi c feet as fol l ows:

Densi t y ( l bs/ f t 3) = wt . ( l b) or

1728 wt. ( l b) or 3. 81 wt. (qm or 6. 24 wt. (gi n)

Vol (f t. ) vol ( i nJ ) VOI ( i n ) VOI (cm)

4.7.2 Cel l si ze. The test speci mens may be any conveni ent si ze or shape

that can be accuratel y measured from bl ocks or S1i ces. The di stance between

f l at s f or t en cel l s i n a row i n t he t ransverse di r ect i on (H) i n si x random

sel ected l ocati ons shal 1 be measured to the nearest 0. 01 i nch. The nomnal

cel l si ze shal l be taken as a tenth of a measured di stance as i l l ust rated i n

Fi gure 2 and the resul ts averaged.

4.7.3 Cel l Di tch. The test speci mens may be any conveni ent si ze or shape

that can be accuratel y measured from bl ocks or S1i ces. The di stance between

nodes for ten cel l s i n a row in the l ongi tudi nal di r ect i on ( L) i n si x random

sel ected l ocati ons shal 1 be measured to the nearest 0. 01 i nch. The nomnal

cel l pi tch shal l be taken as a tenth of the measured di stance as i 1Iustrated

i n Fi gure 2 and the resul ts averaged.

4. 7. 4 Foi l thi ckness. The test speci mens may be any conveni ent si ze or

shape that can be accuratel y measured.

The thi ckness of the foi l shal l be

measured to the nearest 0. 0001 i nch by any sui tabl e method as l ong as no

adhesi ve thi ckness i s i ncl uded. The thi ckness shal l be computed as the

average of ten measurements (see Tabl e I I ).

4. 7. 5 Core fl atw se compressi ve strength at room temperature.

4. 7. 5. 1 Specimens and preparati on.

Specimens for f l atw se compressi ve

strength shal l be 3 i nches square and 0.625 ~ O.010 i nch for Grade B or

0.500 f 0.010 i nch for Grade C i n thi ckness.

The cross secti onal di mensi ons

shal 1 be measured to the nearest 0. 0S i nch.

The testi ng machi ne l oadi ng faces

shal 1 be approxi matel y 4 i nches square.

8


9/30

ML-C-7438G

Care shoul d be taken to prepare the speci men so that the l oaded ends shal 1 be

paral l el to each other w thi n 0.001 i nch and perpendi cul ar w thi n 5 degrees to

the cel l axi s of the speci men.

The surface of the speci men shal l be free of

burrs or tears. The core may be stabi I i zed as detai l ed i n M L-STO-401 to

avoi d l ocal crushi ng of the ends,

4.7.5.2 Procedure. The test procedure shal l be i n accordance w th M L-

STD-401 .

The l oad shal I be appl i ed w th a cont i nuous and constant rate of

movement of the head of the testi ng machi ne at 0.020 ~ 0. 005 i nch per

mnute.

4. 7. 5. 3 Cal cul at i on. The fl atw se compressi ve strength shal l be computed

by di vi di ng the maxi mum l oad by the cross secti on area.

4. 7. 6 Core fl atw se compressi ve strength at el evated temperatures.

4. 7. 6. 1 Specimens and Preparati on.

Speci men si ze and preparati on shal 1 be

as detai l ed i n 4.7.5.1. At the opt ion of the suppl i er ,

, a heat resi stant

adhesi ve bonded sandw ch fl atw se compressi on sampl e of the core may be used

i n I i eu of stabi l i zat i on i n accordance w th M L-STO-401. .

Faci ngs shal l be

0. 020 i nch Al 10Y 2024-T3 or 2024-T131conformng to QQ-A-250/ 4 or c1ad 2024-T3

or cl ad 2024-T81 conformng to @A-250/ 5.

4.7. 6. 2 Procedure. Grade B core speci mens shal l be heated and hel d at

350 ~ I O*F for I O mnutes.

One set of Grade C core shal 1 be condi t i oned

at 350 ~ 10F for 10 mnutes and another set at 430 + 10F for 10 mnutes.

Speci mens shal l be subj ected to the I oad as detai l ed- i n 4.7.5.2 at the

temperature condi ti oned. I f the temperature has been al l owed to vary beyond

the pl us range of 10F from the test temperature, the test shal 1 not be

consi dered val i d.

4.7. 6. 3 Cal cul at i on. The fl atw se compressi ve strength at el evated

temperature shal l be computed as detai l ed i n 4. 7. 5. 3.

4. 7. 7 Shear strength at rcom temperature. For core w th a nomnal densi ty

not exceedi ng 10. 0 pounds per cubi c foot, shear strength shal I be determned

i n two di recti ons (I ongi tudi nal and transverse) by the pl ate shear procedure

(see 4. 7. 7. 1) as detai l ed i n M L-STD-401.

For core w th a nomnal densi t y of

/ 0. 5 pounds per cubi c foot or greater, shear strength shal I be determned by

the beam fl exural shear procedure (see 4. 7. 7. 2) as shown i n Fi gure 3.

4.7.7.1 Pl ate shear . Speci mens shal l be 7.5 by 2 i nches mni mum w th a

thi ckness of 0. 625 f 0. 010 inch f or Grade B or 6 by 2 inches mnimum w th a

thi ckness of 0.500 ~ O.010 i nch for Grade C. Speci mens shal l be bonded to

the l oadi ng pl ates of the apparatus as detai l ed i n M L-STO-401. For test i ng,

the l oad shal 1 be appl i ed at the rate of 0.04 i nch per mnute. Core shear

strength i n pounds per square i nch (psi ) shal I be cal cul ated as fol l ows:

v=&

LB

9


10/30

ML-C-7438G

Where:

V = Shear strength

Pm = Maxi mum l oad (l b. )

L = Length ( i n. )

B = Wdth ( i n. ).

4.7.7.2 Fl exural shear . Speci mens shal l be fabr icated to compr ise an 8 by

3 inches sandw ch w th a 0. 625 f O.Oi O inch core. Faci ng shal l be 0. 1. ?5 i nch

thi ck base 2024-T3 or 2024-T81 conformng to ~-A-250/ 4 or cl ad 2024-T3 or

2024-T81 conformng to QQ-A-250/ 5. Length and w dth of the sandw ch shal 1 be

measured to the nearest 0. 01 i nch.

Speci mens shal I be posi ti oned and l oaded

as detai l ed i n Fi gure 3. The l oad rat e shal l be 0. 015 to O.O2O inch per

mnute. Sandw ch core shear strenqth (Dounds per square i nch) shal l be

cal cul ated as fol l ows:

Where:

v=

P. =

B=

T=

Tc =

v= Pm

B(T+Tc)

Sandw ch shear strength

Maxi mum l oad ( l b. )

Sandw ch w dth ( i n. )

Sandw ch thi ckness (i n. )

Core thi ckness (i n. )

4.7. 8 Shear strength at el evated temperatures. For core w th a nomnal

densi ty not exceedi ng 10.O pounds

per

cubi c foot . shear strenqth shal l be

determned i n two di rect i ons by the pl ate shear procedure as ~etai l ed i n M L-

STO-401 For core w th a nomnal densi ty of 10.5 pounds or more, shear

strength shal l be determned by the sandw ch fl exural shear procedure as shown

i n Fj gure 3.

4. 7. 8. 1 Speci mens and procedures. Speci mens of core shal 1 be as detai l ed

i n 4,7.7.1 or 4.7.7.2 as appl i cabl e for the procedure to be used.

Speci mens

shal l be pl aced i n the testi ng machi ne,

condi t i oned by heati ng as detai l ed i n

4.7.6.2 and then subj ected to the l oad as stated i n 4.7.7.1 or ,4.7 .7.2 at the

condi ti oni ng temperature.

If

the temperature has been al l owed to vary beyond

the pI us range of 10F f rom the test temperature, the test shal I not be

consi dered val i d.

4. 7. 8. 2 Cal cul at i on. The shear strength at el evated temperature shal 1 be

cal cul ated as speci f i ed i n 4. 7.7.1 or 4.7.7.2 i n accordance w th the procedure

used.

10


11/30

M L-C=7438G

4. 7. 9 Del amnati on strenqth

4. 7.9.1 At room temperature. The core speci men shal l be 5 ~ 1/ 16 i nches

w de, 10 f 1/ 2 i nches l ong and 0. 625 ~ 0.010 inch thi ck f or Grade B or

0.500 ~ 0.010 i nch thi ck for Grade C.

Wdth shal 1 be paral l el to the node-

to-node bond area. Speci mens shal 1 be tested i n accordance w th M L-STD-401

The test i ng machi ne shal l be capabl e of mai ntai ni ng a steady l oad rate of 1. 0

i nch per mnute of head travel to produce a constant rate of gr i p separat i on.

Fai l ure i n gr ips shal l be consi dered a sat i sfactory test provi ded the val ues

obtai ned are equi val ent or exceed the val ues contai ned i n thi s speci fi cati on.

Del amnati on strength shal l be the U1timate tensi l e force i n pounds.

4.7.9.2 Af ter boi l i ng water i mmersi on. The core speci mens shal 1 be of the

si ze detai l ed i n 4.7.9.1. The core shal l be total l y i mmersed i n boi l i ng

di st i l l ed water for 120 : , 5 mnutes,

removed and cool ed. Wthi n 4 hours

after removal from the bol l i ng water,

speci mens shal 1 be tested for

del amnati on i n a fi xture and the del amnati on strength recorded as detai l ed

i n 4. 7. 9. 1.

4.7.9.3 At el evated temperatures The core speci mens shal i be of the si ze

detai l ed i n 4.7.9.1. Speci mens shal l be pl aced i n the test f i xture, then

heated and hel d at 350 I 10F for 10 mnutes. Speci mens shal I be subj ected to

the l oad at 350 ~ i OF and the del amnat ion st rength recorded as detai l ed i n

4.7. 9.1. [ f the temperature has been al l owed to vary beyond the pl us range of

I OF from 350 F, the test shal l not be consi dered val i d.

4. 7. 10 Corrosi on resi stance.

4. 7. 10. i Test speci mens and preparati on.

Specimens for corrosi on

resi stance shal l be 5 ~ l /16 i nches l ong ( longi tudi nal di rect ion) , 6 1

1/ 16 i nches w de (transverse di rect i on) (see Fi gure 2) and 0.6.?5f 0.010

inch thi ck f or Grade B or 0. 500 + O.010 inch thi ck f or Grade C. Grade B

core shal i be heated i n an el ect~i c dryi ng oven for 16 hours : 15 mnutes at

350 ~ 10F, whereas Grade C shal 1 be heated for 6 hours ~ 10

mnutes at 430 ~ I OF. Speci mens shal i be removed from the oven,

al l owed to cm to room temperature i n a desi ccator before wei ghi ng to the

nearest ml l i gram usi ng an anal yti cal bal ance.

4. 7.10.2 Procedure. The test speci mens shal l be ubj ected to a 5 percent

sal t spray test i n accordance w th ASTM B 117, except that the cel l axi s (WL

axes) shal 1 be supported or suspended hori zontal approxi matel y 90 degrees from

the verti cal .

At the end of 30 days exposure, the speci mens shal l be removed

and ri nsed thoroughl y i n cl ear runni ng water.

I mmedi atel y fol l ow ng ri nsi ng,

the speci mens shal 1 be stri pped by i mmersi on i n a phosphor{ c- chrom c

acid sol ut i on f or 5 mnutes at 212F. The solut i on shal l consi st of t he

fol l ow ng:

Phosphori c aci d, B5 percent

103 ml l i l i ters

Chromc aci d (CrO, )

76 grams

Water, to make

3.75 l i ters

11

The speci mens shal l be removed from the sol uti on, washed i n di st i l l ed or

dei oni zed water, dri ed at 225 ~ 5F for 30 mnutes, cool ed to room temperature

and rewei ghed. The stri ppi ng sol uti on shoul d be di scarded after 3. 75 1i ters

of the sol ut i on has di ssol ved 20 grams of oxi des or coat i ng.


12/30

M L-C- 7438G

4. 7. 10. 3 Cal cul ati on.

The l oss of wei ght as ml l i grams per square foot of

exposed foi l area i s cal cul ated as fol l ows:

M = 36C(0-A)

TLW

Where:

M=

c=

T=

L=

w=

bl ei ght l oss per square foot of exposed foi l

area i n ml l igrams

Nomnal cel l si ze, i nch ( 1/ 8, 5/ 32, 3/ 16, 1/ 4, 3/ 8)

Thi ckness measurement i n di recti on of cel l axi s, i nch

Ri bbon l ength di recti on, i nches

Transverse di recti on, i nches

O = Ori gi nal wei ght

before exposure

A = Fi nal wei ght of

str i ppi ng

of speci men i n ml l igrams

speci men i n ml l i grams after

4.8 Rej ect i on and retest . If

the resul ts of the qual i ty conformance tests

show fai l ure to conform to 3.5 and Tabl e

III, tests

shal l be conducted on the

remai ni ng materi al sampl es hel d for retest (see Tabl e

XVI .

Fai l ure of t he

retest speci mens to conform to the respecti ve requi rements shal 1 then be cause

for rej ect i on of the l ot represented by the mater i al .

5. PACKAGING

5. 1 Preservati on. Preservat ion shal l be Level A or C, as speci f i ed (see

6. 2: 1) .

5.1.1 Level A. Mater ial shal l be preserved i n accordance w th M L-P-116,

Method 111, and packaged i n contai ners conformng to PPP-B-636. For sl i ces or

for more than 1 bl ock per contai ner,

the l ayers of core mater ial shal l be

i nter l eaved w th kraft paper conformng to UU-P-268. Uni t quant i t i es shal l be

as speci f i ed by the procuri ng acti vi ty.

5.1.2 Level C. Mater ial shal 1 be preserved i n accordance w th ASTM O

3951.

5. 2 Packi ng. Packi ng shal l be Level B or C as speci f i ed ( see 6. 2) .

5.2.1 Level B. Mater ial preserved as speci f i ed i n 5.1.1, shal l be packed

in contai ners conformng to PPP-B-576, PPP-B- 585, PPP-B-591 , PPP-B-636

Domesti c Cl ass, or PPP-B-640 Domesti c Cl ass.

Contai ners shal l be cl osed and

strapped i n accordance w th the appl icabl e contai ner speci fi cati on or appendi x

thereto.

12


13/30

M L-C-7438G

5. 2.2 Level C. Material shal I be packed i n accordance wti h ASTM D 3951.

- .

5. 3 Marki ng.

~n addi ti on to any speci al marki ng requi red by the contract

or order (see 6.2.1) , i nter ior and exter ior contai ners shal l be marked i n

accordance w th requi rements of M L-STD-129.

Ai so, the i nter ior and exterior

contai ners shal l be marked w th the code number (see 3. 2. 4)

6. NOTES

* 6.1 I ntended use. The core mater i al covered by thi s speci f i cat i on i s

i ntended for use i n fabri cati ng sandw ch constructi on for ai r frame structural

use and i n weapons systems. The fabri cati on and qual i ty conformance

i nspecti on requi rements for the core materi al detai l ed i n thi s speci fi cati on

shal 1 not beused for the desi gn al l owabl e requi red for sandw ch

constructi on.

6. 2 Orderi ng data.

6. 2. 1 Acqui si t i on requi rements.

Acqui si ti on documents shoul d speci fy the

fol l ow ng:

a.

b.

c.

d.

e.

f .

9.

h.

i .

j

k.

1.

m

Ti tl e, number and date of thi s speci f i cati on.

Grade of materi al (see 1. 2).

Core code number, to i ncl ude densi ty, cel l si ze,

foi l thi ckness, al l oy, etc. ( see 3.2.4) .

Perforati on, i f requi red (see 3. 3. 2).

Bl ocks or sl i ces, di mensi ons of core materi al and

tol erances (see 3. 3, 3).

Mechani cal properti es of speci al core conf i gurati on,

i f appl i cabl e (see 3.8) .

Quanti ty (cubi c feet) of core material (see 4.3) .

Responsibi 1i ty for perf ormance of

(see 4. 5).

Appl i cabl e l evel s of preservati on

and 5. 2).

Speci al marki ngs (see 5. 3).

f i rst art icl e i nspect ion

and packi ng (see 5. 1

Cel l si ze, cel l pi tch and foi l thi ckness determnati ons,

i f requi red (see Tabl es I , II and XVI .

Mechani cal and physi cal testi ng, i f requi red (see Tabl e XVI

kl herethe Fi rst Arti cl e i nspect ion i s to be conducted, i f

requi red.

13


14/30

M L-C-7438G

6.3 Fi rst ar ti cl e test . repor t.

14henFi rst Arti cl e sampl es are submtt ed

(see 6. 2. 1), they shoul d be accompani ed by a compl ete i nspecti on report

show ng the resul ts of the contractors i nspecti ons.

The i nspecti on report

shal l i ncl ude the fol l ow ng:

a. Report of i nspecti ons numeri cal l y presented when possi bl e,

together w th a detai l ed statement i ndi cati ng compl i ance or

extent of noncompl i ance w th al 1 requi rements of thi s speci -

fi cati on, referri ng speci fi cal l y to paragraph numbers.

Wherever a requi rement i s consi dered to be not appl i cabl e,

the report shal l so state.

b. Di agrams of i nspect i on set-ups. A compl ete descr i pt i on of

i nspecti on equi pment and i nspecti on procedures.

c. Nhere i nspect ions speci f i ed i n thi s speci f i cat ion are not

consi dered appl i cabl e, the reason, and the substi tuted i n-

specti on shoul d be cl earl y descri bed.

d. Copi es of i nspect ion l og sheets.

* 6.4 Supersedi ng data.

Where Grade A core materi al s (Al l oy 3003, 5052 and

5056) are speci f i ed to be used as l i sted on appl i cabl e draw ngs, Grade B

materi al shoul d be acqui red as a substi tuti on. Treated materi al may be used

where untreated materi al was used i n previ ous constructi on. Revi si on G was

prepared to cover treated (previ ousl y Cl ass 2) materi al onl y.

6. 5 Measurement of thi ckness of sandw ch cores. To provi de i nformati on

regardi ng the variat i on i n thi ckness of f l at al umnum core materi al and

provi de a basi s for obtai ni ng average thi ckness di mensi ons, the methods

covered i n ASTM C 366. Measurements of Thi ckness of Sandw ch Cores. mav be

used. The methods are desi gnated for measuri ng thi ckness of core as p~oduced

(see 3. 3. 3) and are not i ntended for use i n determni ng di mensi ons of core

speci mens for tests i n thi s speci f i cati on.

a

* 6. 6 Changes from previ ous i ssues.

The margi n of thi s speci f i cat i on are

marked w th asteri sks to i ndi cate where changes (addi ti ons, modi fi cati ons,

correcti ons, del eti ons) from the previ ous i ssue were made. Thi s was done as

conveni ence onl y and the Government assumes no I i abi l i ty whatsoever for any

i naccuraci es i n these notati ons. Bi dders and contractors are cauti oned to

eval uate the requi rements of thi s document based on the enti re content

i rrespecti ve of the margi nal notati ons and rel ati onshi ps to the l ast previ ous

i ssue.

Custodi ans: Prepari ng acti vi ty:

Army - ME Navy - AS

Navy - AS

Ai r Force - 20 (Proj ect 5680-0120)

14

Revi ew acti vi ti es:

Army - MI, MR

Ai r Force - 99

User acti vi ti es:

Army - AV

Navy - OS


15/30

M L-C-7438G

* TABLE I .

Physi cai propert y requi rements.

Characteri sti c Requi rement tol erances

paragraph

Densi ty Ni thi n f 10 percent of the

4. 7. 1

desi gnated or speci f i ed nomnal

val ue ( see Tabl es IV, V or VI I I ,

as appl i cabl e, for the al I oy)

based upon cel l si ze and desi gnated

foi l thi ckness

Cel l si ze ~/

Wthi n ~ 10%of desi gnated

4. 7. 2

val ue

Cel l pi tch ~/

Wthi n +20 percent, - i O percent of

4. 1. 3

desi gnated cel l si ze mul ti pl i ed by

factor of 1.733

J / Shal l be determned when speci f i ed.

TABLE I I . Al umnum core foi l thi ckness, i nch. ~1

Desi gnated

Max i mum Desi gnated

Maxi mum

0. 0007 0. 0011

0.0030

0.0010

0.0042

0.0015

0.0040

0.0053

0. 0015 0. 0022

0.0050

0.0065

0. 0020 0. 0029

0.0060

0.0078

0.0025

0.0034

~/ 5hal l be determned when speci fi ed.

TABLE III. Tabl es of compressi ve and shear strength requi rements.

Room temperature El evated temperatures

Grade

Al l oy

(70 - 85F)

350 ~ 10F

43o ~ 10F

Tabl e Test Tabl e

Test Tabl e

Test

reference

reference

reference

B

5052

I v 4. 7. 5 & I V

4. 7. 6 & -

4. 7. 7

4. 7. 8

5056

v 4. 7. 5 &

VI I

4. 7. 6 & -

4. 7. 7

4. 7. 8

c

2024

VI I I

4. 7. 5 k I x

4.7. 6 &

x

4. 1. 6 &

4. 7. 7

4. 7. 8

4. 7. 8

15


16/30

M L-C-7438G

TABLE I V. Mechani cal properti es of 5052 al umnum honeycomb core at rcom

temperature. ~/

Nomnal

Cel l

Foi I Stabi l i zed

Pl ate shear

core si ze,

thi ckness,

f l atw se

densi t y, i nch

i nch

compressi ve

Longi tudi nal Transverse (W

PCF strength, (L) shear shear

psi

strength,

strength,

psi psi

1, 0

1. 6

1. 6

2. 0

2. 3

2. 3

2. 6

3. 0

3. 1

3. 1

3. 4

3. 7

3. 8

4. 2

4. 3

4. 4

4. 5

5. 2

5. 3

5. 4

5. 7

6. 0

6: 1

6. 5

6. 9

6. 9

; : ;

8. I

8. 1

8. 4

9. 2

10. 0

Io.o

10. 5

10. 6

12. 0

3/ 8

1/ 4

318

3/ 16

114

318

5/ 32

3/ 8

1/ 8

3/ 16

1/ 4

318

5132

318

1/ 4

3/ 16

1/ 8

1/ 4

5132

318

3/ 16

I / 4

118

318

5132

3/ 16

318

1/ 4

1/ 8

3/ 16

5132

1/ 4

1/ 8

5132

1/ 4

3/ 16

1/ 8

0.0007

0.0007

0.0010

0.0007

0.0010

0,0015

0.0007

20 32

20

70

60

32

70 60

32

00 80

46

30 100 57

30

100 57

60

120

0. 0020 200 145 :

0.0007

0. oo1o

0.0015

0.0025

0.0010

0.0030

0.0020

0.0015

0.0010

0.0025

0.0015

0.0040

0.0020

0.0030

0.0015

0.0050

0.0020

0.0025

0.0060

0.0040

0.0020

0.0030

0.0025

0.0050

0.0025

0.0030

0.0060

0.0040

0.0030

215

215

250

290

300

360

370

385

405

510

535

540

600

660

680

760

800

800

I000

1050

1100

I l oo

1180

1330

1500

I 500

1600

1620

I 91O

155

155

180

205

215

255

265

280

285

360

370

380

410

445

455

500

540

540

615

650

670

670

690

780

860

860

1120 ~J

1130 ~1

1250 ~1

n

105

120

125

150

155

160

168

200

215

228

244

265

272

300

328

328

370

390

400

400

420

455

490

490

640 ~1

650 ~1

750 ~1

~/ Val ues are for test purposes onl y.

Data shal 1 not be used for desi gn

al l owances.

~/ Shear strength val ues determned by Beam Fl exure Shear.

16


17/30

ML-C-7438G

TABLE V. Mechani cal properti es of 5056 al umnum honeycomb core at room

temperature. ~/

Nomnal

Cel l Foi I

Stabi l i zed

Pl ate shear

core si ze, thi ckness, f l atw se

densi ty,

i nch i nch

compress~ve

Longi tudi nal

Transverse (N)

PCF

strength, (L) shear shear

psi strength, strength,

psi

psi

1. 0

1. 6

1. 6

2. 0

2. 3

2. 3

2. 6

3. 0

3. 1

3. I

3. 4

3. 7

3. 8

4. 2

4. 3

4. 4

4. 5

5. 2

5. 3

5. 4

5. 7

6. 0

6. 1

6. 5

6. 9

6. 9

7. 6

7. 9

8. 1

8. 1

8. 4

9. 2

10. 0

10. 0

10. 5

10. 6

12. 0

3/ 8

I 14

318

3/ 16

l / 4

3/ 8

5i 32

3/ 8

118

3/ 16

1/ 4

318

5/ 32

318

114

3/ 16

118

I 14

5132

318

3/ 16

I f4

118

318

5132

3/ 16

3/ 8

114

I / 8

3}16

5/ 32

l / 4

118

5132

I 14

3/ 16

l / 8

0.0007

0.0007

0.0010

0.0007

0.0010

0.0015.

0.0007

0.0020

0.0007

0.oo1o

0.0015

0.0025

0.0010

0.0030

0.0020

0.0015

0.0010

0.0025

0.0015

0.0040

0.0020

0.0030

0.0015

0.0050

0.0020

0.0025

0.0060

0.0040

0.0020

0.0030

0.0025

0.0050

0.0025

0.0030

0.0060

0.0040

0.0030

35

80

80

I20

155

155

185

250

260

260

315

362

375

443

465

490

500

645

650

680

735

805

825

908

1000

1000

1155

1265

I300

1300

1375

I570

1760

1760

1900

1920

2270

45

78

78

105

I30

130

152

190

200

200

230

260

272

31s

325

340

350

425

435

450

480

512

525

568

610

610

687

720

740

740

175

865

950

950

1175 2/

1180 ~1

1375 ~1

25

38

38

%

: ;

100

110

110

130

150

155

180

190

198

205

245

250

260

280

300

305

335

360

360

410

430

440

440

455

500

538

538

700 21

710 7t

820 ~1


Oata shal l not be used for desi gn

al l owances.

~/ Shear strength val ues determned by Beam Fl exure Shear.

17


18/30

ML-C-743EI G

TABLE VI .

Mechani cal propert i es of 5052 al umnum honeycomb core

at 350 *

I OF. ~/

omn l

Cel l

Foi l

Stabi l i zed

Pl ate shear

core

si ze, thi ckness,

fl atw se

densi ty,

i nch

i nch

compressi ve

Longi tudi nal

Transverse (H)


psi

strength,

strength,

psi psi

1. 0

1. 6

1. 6

2. 0

2. 3

2. 3

2. 6

3. 0

3. 1

3. 1

3. 4

3. 1

3. 8

4. 2

4. 3

4. 4

4. 5

5. 2

5. 3

5. 4

5. 7

6. 0

6. 1

6. 5

6. 9

6. 9

7. 6

7. 9

8. 1

8. 1

8. 4

3/ 8

114

3/ 8

3/ 16

I 14

3/ 8

5/ 32

3/ 8

118

3/ 16

114

318

5132

318

1/ 4

3/ 16

I l a

I f4

5/ 32

3/ 8

3/ 16

114

118

3f8

5/ 32

3/ 16

318

I / 4

118

3/ 16

5/ 32

0.0007

0.0007

0.0010

0.0007

0.oo1o

0.0015

0.0007

0.0020

0.0007

0.0010

0.0015

0.0025

0.oo1o

0.0030

0.0020

0.0015

0.0010

0.0025

0.0015

0.0040

0.0020

0.0030

0.0015

0.0050

0.0020

0.0025

0.0060

0.0040

0.0020

0.0030

0.0025

13

43

43

62

82

82

105

131

141

141

164

190

197

236

243

253

262

335

341

367

394

433

446

499

525

525

656

6B9

722

722

774

22

42

42

56

70

70

84

102

109

109

126

144

151

179

186

196

200

252

259

266

287

312

319

350

378

378

431

455

469

469

483

13

21

21

30

37

37

46

55

59

: :

78

81

9B

10}

104

109

130

140

148

159

172

177

195

213

213

241

254

260

260

273

18


19/30

M L-C-7438G

TABLE VI . Mechani cal

propert i es of 5052 al umnum honeycomb core

at 350 ~ IOF. ~/ - Cont inued

Nomnal

Cel l

Foi I

Stabi l i zed

Pl ate shear

core si ze,

thi ckness,

f l atw se

densi ty, i nch

i nch

compressi ve Longi tudi naI Transverse (w)

PCF

strength, (L) shear

shear


psi

psi

9. 2

I 14

10. 0

1/ 8

l oo 5132

10. 5

1 4

10. 6

3/ 16

12. 0 118

j , / Val ue5 are f or

al l owances.

~/ Shear strength

TABLE VII.

0.0050

872 546 296

0. 0025 981 602 319

0. 0030 98]

602

319

0.0060

0.0040

0.0030

1060

1063

1263

785 21

790 2J

875 2}

325 21

325 ~t

325 ~1

test purposes onl y. Data shal l not be used for desi gn

val ues determned by Beam Fi exure Shear.

Mechani cal propert i es of 5056 al umnum honeycomb core

at 350 ~ 5F. ~/

Nomnal

Cel l Foi 1

Stabi l i zed

Pl ate shear

core si ze,

thi ckness, f l atw se

densi ty, i nch

i nch compressi ve

Longi tudi nal

Transverse (N)

PCF

strength,

(L) shear

shear

psi

strength,

strength,

psi

psi

1. 0 318

0.0007

23

29

1. 6

l b

I14

0. 0007 49 51

1. 6

25

318

0. 0010 53

51

2. 0

25

3/ 16

0.0007

72

68

2. 3

I14

33

0.0010

I02 85

2. 3

40

318 0. 0015

102 89

2. 6

40

5132 0. 0007

117 99

3. 0

52

3/ 8 0. 0020

I68 124

3. 1

118

65

0. 0007 i62

3. 1

130 72

3/ 16 0. 0010 175 130

3. 4

72

I / 4

0. 0015 210

150

3. 7

85

3/ 8 0. 0025 235 169

3. 8

98

5132 0. 0010 252

177

4. 2

101

318 0. 0030 287 205

4. 3

117

114

0. 0020 308 211

4. 4

124

3/ 16 0. 0015

322

221

4. 5

129

118

0. 0010 333

5. 2

228 133

114

0. 0025 420 276 159

19


20/30

M L-C-7438G

TABLE VI I . Mechani cal properti es of 5056 al umnum honeycomb core at

350 f 5F. ~/ - Cont inued

Nomnal

Cel l

Foi 1 Stabi 1i zed Pl ate shear

core

si ze, thi ckness,

f l atw se

densi t y, i nch

i nch

compressi ve

Longi tudi nal

PCF

Transverse (W

strength,

(L) shear

shear

psi

strength,

strength,

psi

psi

5. 3 5132 0. 0015

431

283

163

5. 4 3/ 8 0. 0040 441

293

169

5. 7 3/ 16

6. 0

1/ 4

6. 1

118

6. 5 318

6. 9

5132

6. 9 3/ 16

7. 6

318

7. 9 1/ 4

8. 1 1/ 8

8. 1 3. 16

8. 4 5J 32

9. 2

1/ 4

10. 0 1/ 8

10. 0

5132

10. 5 114

10. 6

3/ 16

12. 0 1/ 8

0.0020

0.0030

0.0015

0.0050

0.0020

0.0025

0.0060

0.0040

0.0020

0.0030

0.0025

0.0050

0.0025

0.0030

0.0060

0.0040

0.0030

480

518

532

636

700

700

809

886

910

910

963

1099

1232

1232

1330

1344

1589

312

333

34I

369

397

397

441

468

481

481

504

562

618

618

820 ~1

825 ~1

965 ~1

182

195

198

218

234

234

267

280

286

286

296

325

350

350

350 ~1

350 I I

350 ~1

~/ Val ues are for test purposes onl y. Data shal l not be used for desi gn

al l owances.

~/ Shear strength val ues determned by 8eam Fl exure Shear

20


21/30

M L-C-7438G

TABLE

VIII.

Mechani cal propert i es of 2024- T81 al umnum honeycomb core at

room temperature. ~/

Nomnal

Cel 1

Foi l

Stabi 1i zed

Pl ate shear

core si ze, thi ckness,

f l atw se

densi ty, i nch i nch compressi ve Longi tudi nal

Transverse (W


psi

strength,

strength,

psi

psi

2. 8 l / 4 0. 0015 175

I 40 8f J

3. 5

3/ 16

0. 0015 290 230

I43

5. 0

118

0. 0015 620

400

250

6. 7 118

0. 0020 980

600

375

8. 0

I i 8

0. 0025 1320

710

470

9. 5

118 0. 0030 1725 950

585


Oata shal l not be used for desi gn

al l owances.

TABLE I X. Mechani cal properti es of 2024- T81 al umnum honeycomb core

at 350 ~ 10F. ~/

Nomnal

Cel l

Foi l Stabi l i zed

Pl ate shear

core si ze,


densi ty, i nch i nch

compressi ve

Longi tudi nal

Transverse (N)

PCF strength, (L) shear

shear


psi

psi

2. 8

I 14

0. 0015 140

105

60

3. 5

3116

0.0015

230

170 100

5. 0

118

0.0015

495

300

175

6. 7 I / 8 0. 0020

785

450

260

8. 0 118 0. 0025

I055

580

330

9. 5 1/ 8 0. 0030

1380

715

410

~/ Val ues are for test purposes only. Data shal I not be used for desi gn

al l owances.

21


22/30

M L-C-7438G

TABLE X. Mechani cal properti es of 2024-T81 al umnum honeycomb at

430 * 10F.

~1

Nomnal

Cel l

Foi 1

Stabi l i zed

Pl ate shear

core

si ze,


densi ty, i nch i nch

compressi ve Longi tudi nal Transverse (H)

PCF

strength, (L) shear shear


psi psi

2. 8

1/ 4

0. 0015 120 90

3. 5

52

3/ 16

0.0015

200

150

5. 0

85

1/ 8

0. 0015 435

260

6. 7

118

150

0.0020

685

390

8. 0

225

118

0. 0025 925 500

9. 5 1}8

280

0.0030

1210

620

350

~/ Val ues are for test purposes onl y,

Data shal I not be used for desi gn

al l owances.

TABLE XI . Del amnati on strength of 5052 and 5056 al umnum core materi al

(Grade 8) i n pounds l oad (force)

Nomnal

Test condi ti ons

core

Room temperature

After boi I i ng

350 f 10F

densi ty,

(70 to 85F)

water i mmersi on

PCF

.

Strength, mni mum

Strength, mni mum

Strength, mni mum

l . oto 3. 1,

30

10 10

3. 4 to 7. 9, 40

10 20

8. 1 t o 12. 0

50

10

25

22


23/30

M L-C-7438G

TABLE XI I . Del amnati on strength of 20. 24al umnum core materi al

(Grade C) i n pounds l oad (force).

Nomna1

Cel l

Foi I

Test condi ti ons

core

si ze,

thi ckness,

densi ty, i nch i nch Room temperature After boi 1i ng

PCF

350 f IOF

(70 to 85F)

water i mmersi on

Strength, mni mum Strength, mni mum Strength,

mnimum

2. 8 1/ 4 0. 0015

30

25

10

3. 5 3/ 16

0.0015

40

25

10

5. 0

118 0. 0015

55

30

15

6. 7

1/ 8

0.0020

70

15

B.O

118

0. 0025 75

; :

15

9. 5 118

0.0030

90

40

15

TABLE

XIII. Color code identification

for Grade B.

Col or

FEO-STD-595 Al umnum Al l oy

Col or No.

5052 5056

Bl ack ~/ ~/

Two bl ack j / ~/

Densi ty range - PCF

Brown

Orange

81u&

Red

Yel l ow

Purpl e

Green

8rown and

green

Brown and

purpl e

10076

12246 or 22246

15102 or . 25102

11105 or 21105

13655 or 23655

17142 or 27142

14187

10076 and 14187

10076 and 17142 or

27142

Up to 1.9, i ncl usi ve

2.0 to 2.9, i ncl usi ve







Over 11. 0

~/ Bl ack shoul d match Col or No. 17308 or 27308 of FED-STO-595.

ZI One bl ack st ri pe al ong

~/ Two bl ack st ri pes, one

si de of requi red densi ty col or (

on ei ther si de of requi red dens

23

ode.

ty col or code.


24/30

M L-C-7438G

TABLE XI V, Col or code i denti f i cat i on for Grade C.

Col or

FEO-STD-595

Nomnal densi ty -

Col or No.

PCF

Yel l ow 13655 or 23655 2. 8

Red 11105 or 21105

3. 5

Purpl e

17142 or 27142 5. 2

Green

14187 6. 7

Bl ue

15102 or 25102 8. 1

Bl ack

17308 or 27308 9. 5

TA8LE

xv

Vi sual i mperf ecti ons (maxi mum number i n a

square foot of materi al ) .

Imperf ect i on t ypes Accept ance number of vi sual imperf ect i ons

for cel l si ze i n i nch

1/ 8

5/ 32

3/ 16 1/ 4

3/ 8

Msmatched nodes

90

70

50 30

13

Loose metal or f l akes ~/ 45

35

25

15 6

Unbended nodes

2 2

2

2 2

Spl i t cel l wal l s

o

Buckl ed cel l wal l s

o

~/ Fl akes are excess metal attached to foi 1 edges whi ch do not i nter fere w th

core thi ckness measurement.

TABLE

XVI

Qual i ty conformance testi ng.

Number of

Materi al

speci mens

Reference . Conform ng to

Tests grades requi red paragraph paragraph

Core densi ty

B and C 1 ~1

4. 7. 1

3.4 and Tabl e I

Cel l si ze ~/

B and C

I 4. 7. 2

3.4 and Tabl e I

Cel l pi tch ~/ B and C

I 4. 7. 3

3.4 and Tabl e I

Foi 1 thi ckness ~/

B and C

I 4. 7. 4

3. 4. 1 and Tabl e II

24


25/30

M L-C-7438G

TABLE XVI .

Qual i ty conformance testi ng, - Conti nued

Number of

Materi al

sDeci mens

Reference Conferm nq to

Tests

grades

requi red

paragraph

paragra~h

Core f l atw se B and C 6 ~1 4. 7. 5

3.5, Tabl es I I I ,

compressi ve strength

IV,

V and VI I I

at room temperature

Core fl atw se

compressi ve strength

at el evated tempera-

ture, 350 f 10F

Core f l atw se com

pressi ve strength at

el evated temperature,

430 ~ 10F

Transverse (W shear

strength at el evated

temperature, 350 f

I OF

Transverse (H) shear

strength at el evated

temperature, 430 f

I OF

Del amnati on strength

at room temperature


aft er boi 1i ng water

i mmersi on


at el evated temperature

Corros i on resi stance

~1

c

B and C

3

B and C

3

B and C

3

B and C 5

4. 7. 6

4. 7. 6

4. 7. 8

4. 7. 8

4. 7. 9. 1

4. 7. 9. 2

4. 7. 9. 3

4. 7. 10

3. 5, Tabl es 111,

VI and VII

3.5, Tabl es 111

and X

3. 5, Tabl es 111

VI and VI I

3. 5, Tabl es 111

and X

3. 6 and Tabl es

XI and XI I

3. 6 and Tabl es

XI

and XI I

3. 6 and Tabl es

XI and XI I

3. 7

~/ The same sampl e used for the core densi ty may be used for speci mens of the

strength tests, cel l si ze, eel ) pi tch and foi l thi ckness.

Z/ The speci mens sel ected for compressi ve and shear strength shal l be di vi ded

i nto two equal parts; one part shal l be avai l abl e for the requi red qual i ty

conformance tests and the other part shal I be retai ned for retests (see

4. 8) i f necessary.

~/ Shal 1 be determned when speci fi ed.

~/ Select i on i n accordance w th 4.6. ) .3

25


26/30

M L-C-7438G

DOUBLE

FOILS

WI, \

4L\ i (

c

f . 415h4ATCHEDNODES

Fi gure 1.

26


27/30

M L-C-7438G

u

,,

,,

,,

-1

s

Fi gure 2.

27


28/30

M L-C-7438G

I--2--P--2--I

B

SPECI MEN WDTH (3I NCHES)

T SPECI MEN THI CKNESS

Tc CORE THI CKNESS

TF - FACI NG THI CKNESS

END SUPPORT PLATES ARE 1 BY 3 BY 1/4 INCHES WIOTH GROOVES

FOR ALIGNMENT.

LOADED EDGES ARE ROUNDED TO 0.06 INCH RADIUS.

LOAD BARS ARE 1/2 INCH ROUNO.

DIMENSIONS IN INCHES.

TOLERANCES: AS INDICATED.

Fi gure 3.

28


29/30

INsTRUCTIONS: In a continuing ffort ti nuke ..r .t-dudization d.xumenu better, the 00D provides this form for we in

submitkirw comments -d msmstiont for imwo-n=nts. AU US- of udlihw .tandmdization docume. u are invited to pro?ide

mss-tiow. ~U form UMY b= d=f-h=d. folded .1OIIS the tin- indi~t4 w-d ~0.s th. l-e edge 00 NOT sTAPLE md

mailed. En block 6, be u mecific a pible about Partidm

problem-as wA u wordingwhichrequirednhrpretatio.,as

toorigid,eaticti?e,0LW,UZWU.UL. or.- incomxtib e,ndsile

Propcud murdhg

chsngeawhichwouIdslf.via~he

pmbleam. Enter in block 6 my ICMULJ not rehted to spec i f ic parqmpb of the dcmunent. If black 7 u fried out, an

scknowledwnent witl be tied t. YOU with,. 30 chYm to let You know that Your commen~ were mcei~edand are Ktng

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NOTE: This form IMY not be

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1 rew c st c opi m of

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m=ifi=tionmwdremenu on ~~nt cO.lrE@. ~mmen~ .ub~l:~ .. thb rorMdo .ot..nstitutirimply

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LO waive my

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ocument s) or to

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(Fold

don, lhb 11.)

DEPARTMENTOF THE NAVY

111111 F]

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0FFf13AL mmfwss

PENALTY Fon RIVATE usE smo

BUSlNE:SNoR2E~;~H,MT~ ,

F,RST CLASS

mSTAGE WILL BE PAID Ov Tti E Department OF THE NAVY

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MIL-C-7438 Core Material Aluminum for Sandwich Construction Rev G