Structural sandwich construction


Material Information

Structural sandwich construction
Physical Description:
5 p. : ; 26 cm.
Forest Products Laboratory (U.S.)
University of Wisconsin
United States Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:


Subjects / Keywords:
Sandwich construction   ( lcsh )
Structural engineering   ( lcsh )
bibliography   ( marcgt )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


Includes bibliographical references (p. 5).
General Note:
Caption title.
General Note:
"April 1952"--Cover.
General Note:
"In cooperation with the University of Wisconsin"--Cover.
General Note:
"Preliminary copy for review only"--Cover.
Statement of Responsibility:
Forest Products Laboratory, Forest Service, U.S. Department of Agriculture.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029511765
oclc - 757556379
System ID:

Full Text

April 1952

(Prcliminary Copy for lcvictu Only)

No. 11903-11

Madison 5, Wisconsin
In Cooperation with the University of Wisconsin


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Digitized by the Internet Archive
in 2013

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Forest Pr'ducts La1
U. S-. .Farti

tr Frt r r
"t 01 -.r'' rut' I

Structur'.l santKch cs. structi.on is a i:r c -..trui to 0 .
t-' 7in facing to a tIiick c)rc. 1,ne thi: acirs .n. ... 'i' 2
dc:se r.c. r la1 si.c t.;y aro the r.'. .
(2. i tru 2... Thr corc Ii cI is of a 'oakcr li . ........1.;..h 7
and s ca :,lizc s, th<; thin]. "ac'!n;,s ,:nd carrie ,; _s [:hcarx' i ,, ; Ina ""h ": ~
4ass2 ': 17b. pr-vid 2s a structural clement, o strn.. tt 2 s( I...
ptio toits i2bht. Sa'dvdc, construotilon is ;' :C:1o;L: .
nKo Li s0 I)" L us 3,i t' c c r : a.... r" 7
core 1atials arc. usually i-xonsiv. atr s arc ;.t c ...
ecrhc is usoxd to i Ls best a*t!onfoa .
Speci.i nonstrucbur ad,ata:s n ... bo incorpo'"at:.d in a, Eind",;i-c, c'
tai a,-, ao s.. -
t2-- Ap.'i .Lcticn o 1, fa cin., .id cor matroals .A'; ix'".....
(2 O 2 i ~ '.'t2 iC~ 17I. '217l'or fo r r 2: 1,] 12 r I -
can,,- o e oyd to act as a r::"rricr for .....
hose- an 'rLa2sion-r1sistant fcin. ca. be Is.d for tr t,'p faci' .
anL; and -c .ra ivo effects can 1c otain-d I-' usin. ; I ...'
plastic fcin2 s fo. 'r .i.s. n, d s t : ther1 ii o."
ril can b c'son to 1 rovid: thcrrnma insulation fir. resistc n .

serv ic r
5.. 171 i o.2 ,

should 1-be

Sar1-s of th. sann.wich construction shn ouirt rmrnLs. ,)oistur -re4sist&nt IaCingss cor('2 and a2. i'. should
'- if txh: construction is o bo ",d t a'.. unS
~, hc.t-r ,ist2 epsor tco av'-rosist.nt ffcins, co.s c ,n ad....'ie
used if x dour tox >j- -t u rc17 t c Is or deca ort .c....1o is C x-

Str;ctura! n f ...n..L..' truction

The structural dcsin of sad-!.vich constructio-n ma.y b c
of an >D-.,; th ffcinn of the n'.,' r0pr's1nt .ho-
ani th su ,ic co .rr rop'a.sents th 1-1 ... .... I x c
il221722' c
s rves, throuph the oondin a dh.. ....... t' cr stirarinp_
tf 21., f. i. s .L: t l t r n .u" .... o

In 1ncra] th2 1. -11-.. is to 'rovi7 .[a1:n.s t:hic.: noucr
17r,5ssion J 2. ... ts str'ss -s rdi tr_ 1 t' 2. c' r112

2.17217.1 t ~ I .1.27
I1t2'~ 2 1 .17,
U .~ 1- ''
Pt' I I.

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a floor
:.'/" .1 or

lJintaincd rt '.>'.l:on, ) is., in coo rrt ion tih iii 'f-,: oi it,, .sin.

enough to impart stiffness and bending strength to the construction. The
core sho-ld be strong enough to carry the required shearing loads. The con-
struction should bo checked for possible buckling, as for a column or panel
in com. pesion, ond for possible wrinkling of the facings.

The core material itself is assumed to contribute nothing to the stiffness of
the sandwich construction, because it usually has a low modulus of elasticity.
The facing moduli of elasticity are usually at least 100 times as ;r' at as
the core modulus of elasticity. The core material ma-,' also have a small shear
mod-Lus. This small shear modulus causes increased deflections of sandwich
constructions subjected to bending and decreased buckling loads of columns
and edge-loaded panels, compared to constructions in which the core shear
modIlus is large. The effect of this low shear modulus is greater for sortt
beams and columns and small panels than it is for long beams and columns and
lar ge panels.

The stiffness of a strip of unit width of sandwich construction having facings
of equal or unequal thickness is given by:.

D = flf 2E1E2 (h + c)2
4(f l S + '2_2)


D = stiffness per unit width of sandwich construction (redurct
of moduiilus of elasticity and moment of inertia of the cross

f, f2 = facing thicknesses

E, E = moduli of elasticity of the facings

h = total sandwich thickness

c = core thickness

Ihe stiffness is used to compute the deflections and the buckling loads of
sandwich panels.

The midspan deflection of a panel of sandwich construction, with simply
supported ends and free edges, under a uniform transverse load is given by:

w = Pa3 + 192 cD
3 3 2 2 c
a G n *+ C)
' _

pt. No. 1903-11


,; = Iicdc deflecti:

.1 1' Cu


C ,'' ' I"

I +


CiV '13 -

= t' .i. <:;'- ; Lt! 1 ,C

<.' c .:7 is ^r.

= r ti'~:. -

i.i K '~ I
L rj

7T .. ;

V ___ ____-- B

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a = column lcngthi

= p 1anl w;idth

cT prcdin. formulas are basically those needed for the design of sandwich
cnstr uctis. Formulas have 'ibcn derived for various oad .nd d, con-
dai0 uns for constructions of orthotroe;ic or isotropic materials. The: oavior
of thin facinms in regard to .,rinklin" nd core shear failure h 'as ) boen
ivesuatdo . natLyses of these k..ore, specific problems of desin mray bo
fIui. i in rd> fri.c,: (1, 3, 7, 2

Manufacture of Sandvich Construction

Te prin3ipal operation in the manufacture of sandwich construction is the
bonding of te facing s to the cori. T e bonding operation nay involve the
us, of a hot press if pressure and elvated tcnmperatvre are needed to cure
the adesive. Li ht pr ssurcs shouId be used for wieak core trit'-ls to
prevent bh.m from crushing. Som ad ,. s es may rO uire only contact pressure
and no he ting. The process should b. controlled to obtain good facing :-to-
core bonds, since poor bonding ,-trial_ reduce s stiffness as .Tcll as

Tihe facing nmatcril.s may nc.d to b1 cl.anod and ri:,.,d before the adhesive is
app I d, especiailT if they are'r m Ctliic.

Te core maYterial mavf necd to bc for d. ,, bonded to. eth-.r before th, fac-
in s c.n bc applied. Some cor nmateri 'ls my need a glue. size hef fre good
bei.g t tthe facin,- en be obtain d.

In certain sand Vich pnels, loadin. rails or cig are po lae':d bltvrc.. the
facing s at th time of assmbl Spci: fittings or equipment, such as
heatini, plumbing, or l..ctrical wj-rinj conduit, can b, plced nore
iI te a1 during m-nufact t .U'c fter it is completed.

Fr1ther information on faricaboun pr-codurcs for different kinds of sand-iich
cons truct c n is given in riferoencens 1` 7, 1))

undcrlinod numbers In pamrnthuse- refer to Literature Cited at end of this
reo, ort.


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S -T ED It C.O', r -o, .. irs products Llo -t
NoU Il 65 ( pp., il1'u

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