Environmental Engineering Reference
In-Depth Information
Expanding. Equation. (2.51),. criterion. of. strength. for. triaxial. stress. condi-
tions.is.obtained.as:
2
2
2
2
2
2
σ
+ c
σ
+ b
σ
+ d
τ
+ p
τ
+ r
τ
+ s
σ σ
+ t
σ σ
+ f
σ σ
x
y
z
xy
yz
zx
x
y
y
x
z
x
≤
σ
bx
.
. .
2
2
2
2
2
2
σ σ
)
1 2
(
σ
+
σ
+
σ
+
τ
+
τ
+
τ
+
σ σ
+
σ σ
+
x
y
z
xy
yz
zx
x
y
y
x
z
x
.
.
(2.52)
where:
c =
X
Y
; b =
X
Z
; d =
X
; p =
X
S
r =
X
S
;
;
S
12
23
13
.
r - 1
.
(2.53)
4X
S
4X
S
4X
S
s =
- c - d - 1; t =
- c - b - p; f =
- b -
45
12
45
45
23
1,3
All.coeficients.get.by.test.laminates.spaces.
Here:
X,Y,Z.is.a.tensile.(compression).strength.in.x,.y,.z.directions;
X
45
,.Y
45
,.Z
45
.are.the.normal.strength.to.act.in.diagonal.directions;
S
12
,.S
13
,.S
23
.are.the.shear.strength.to.act.in.plane.xy,.and.out.of.plane.xz,.yz;
S
45
12
,. S
45
13
,. S
45
23.
are. the. shear. strength. to. act. in. diagonal. directions. under.
angle.45°.in.plane.xy.and.interlaminar.planes.xz,.yz;
σ
x
,.σ
y
,.σ
z
,.τ
xz
,.τ
yz
,.τ
xy
,.and.τ
zx
.are.normal.and.shear.variable.stresses,.respec-
tively,.and.depends.on.loading.history.
For.biaxial.stress.conditions,.practical.calculation.strength.criteria.look.like:
2
2
2
σ
+ c
σ
+ d
τ
+ s
σ σ
x
y
xy
x
y
)
1 2
≤
σ
.
.
(2.54)
bx
2
2
2
(
σ
+
σ
+
τ
+
σ σ
x
y
x
x
y
The.strength.of.iberglass.comes.from.textile.that.has.been.prepreged.by.
epoxy.resins,.which.are.listed.in.Table 2.2.(all.characteristics.are.in.MPa/psi).
Parameters.for.related.strength.of.iberglass.are.shown.in.Table 2.3.
Equation.(2.52).reduces.to.tensile(compression).stress.σ
x
.,.if.σ
x
.equal.σ
y.
and.
shear.stress.equal.¼.σ
x.
and.parameters.for.calculus.from.Table 2..2.are.used.
In.case.of.tensile.load,.Equation.(2.52).looks.like:
.
3.93σ
x.
≤.[σ
bx
].
(2.55)
In.case.of.a.compression.load,.Equation.(2.52).looks.like:
.
5.93σ
x.
≤.[σ
bx
].
(2.56)
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