Fibre-reinforced and sandwich composites with laminated faces are the best candidate materials in many engineering fields by the viewpoint of the impact resistance, containment of explosions, protection against projection of fragments, survivability and noise and vibration suppression. Besides, they offer the possibility to be tailored to meet design requirements. A great amount of the incoming energy is absorbed through local failures. The most important energy dissipation mechanisms are the hysteretic damping in the matrix and in the fibers and the frictional damping at the fiber-matrix interface. The dissipation of the incoming energy also partly takes place as a not well understood dissipation at the cracks and delamination sites. As self-evident, the local damage accumulation mechanism on the one hand is helpful from the standpoint of energy absorption, on the other hand it can have detrimental effects. To date sophisticated computational models are available, by which the potential advantages of composites can be fully exploited. A large amount of research work has been oriented to improve the impact resistance, the dissipation of vibrations and to oppose the propagation of delamination. These goals can be obtained with incorporation of viscoelastic layers. Unfortunately this makes quite compliant the laminates and reduce their strength. Studies have been recently published that seeks to comply stiffness and energy dissipation. The existence of fiber orientations that are a good compromise between optimal stiffness and optimal absorption of the incoming energy can be supposed by the results of a number of published studies. In this paper, a variable spatial distribution of plate stiffnesses, as it can be obtained varying the orientation of the reinforcement fibres along the plate and their constituent materials, is defined by an optimization process, so to obtain a wanted specific structural behaviour. The key feature is an optimized strain energy transfer from different deformation modes, such as bending, in-plane and out-of-plane shears. Suited plate stiffness distributions which identically fulfil the thermodynamic and material constraints are found that make stationary the energy contributions and transfer energy between the modes as desired. An application to low velocity impacts and to blast pulse loads is presented. The use of the optimized layers with the same mean properties of the layers they substitute were shown to reduce deflection and the stresses that induce delamination. A new discrete layer element is developed in this study, to accurately account for the local effects. Characteristic feature, it is based on a C° in-plane approximation and a general representation across the thickness which can either represent the kinematics of conventional plate models or the piecewise variation of layerwise models.

1.
Bert
CW
.
Composite materials: a survey of the damping capacity of fiber reinforced composites
.
ASME AMD-38
,
1980
:
53
63
.
2.
Abrate S. Impact on Composite Structures. Cambridge University Press, 1998.
3.
Bolotin
VV
.
Delaminations in composite structures: its origin, buckling, growth and stability
.
Composites: Part B
1996
;
27
:
129
145
.
4.
Paris F. A study of failure criteria of fibrous composite materials. NASA/CR-2001-210661 2001.
5.
Tennyson RC, Wharam GE. Evaluation of failure criterion for graphite-epoxy. NASA CR-172547 1985.
6.
Icardi U, Locatto S, Longo A. Assessment of recent theories for predicting failure of composite laminates. Appl Mech Rev. In press.
7.
Bathe
KJ
.
On reliability in the simulation of structural and fluid flow response, Advances in computational methods for simulation
,
Civil-Comp Press
1996
:
1
7
.
8.
Noor
AK
.
Computational structures technology-leap frogging into the twentyfirst century, Advances in computational structures technology
,
Civil-Comp Press
1996
:
1
18
.
9.
Noor
AK
,
Burton
WS
,
Bert
CW
.
Computational models for sandwich panels and shells
.
Appl Mech Rev
1996
;
49
(
3)
:
155
199
.
10.
Reddy JN. Mechanics of Laminated Composite Plates and Shells: Theory and Analysis. 2ND Edition, CRC Press, Boca Raton, FL., 2003.
11.
Tenek LT, Argyris J., Finite element analysis for composite structures. Kluwer Academic Publ., 1998.
12.
Reddy JN. Mechanics of Laminated Composite Plates and Shells: Theory and Analysis. 2ND Edition, CRC Press, Boca Raton, FL., 2003.
13.
Cox
BN
.
Constitutive Model for a Fiber Tow Bridging a Delamination Crack
.
Mechanics of Advanced Materials and Structures
1999
;
6
(
2)
:
117
151
.
14.
Suzuky
K.
,
Kageyama
K.
,
Kimpara
I.
,
Hotta
S.
Vibration and Damping Prediction of Laminates with Constrained Viscoelastic Layers
.
Mechanics of Advanced Materials and Structures
2003
;
10
(
2)
:
43
73
.
15.
Setoodeh S., Abdalla M.M., Gurdal Z., Tatting B. Design of variable-stiffness composite laminates for maximum in-plane stiffness using lamination parameters. 46th AIAA/ASME/ASCE Struc., Struct. Dynam and Appl. Conf., 13th AIAA/ASME/AHS Adap. Struc. Conf., 7th AIAA Non-Determ Appr. Forum, 2005, AIAA 2005-2083: 3473–3481.
16.
Zinoviev PA, Ermakov YN. Energy dissipation in composite materials. Technomic Pub. Co., 1994
17.
Georgi
H.
Dynamic damping investigations on composites
.
Proc. 48th Meeting AGARD, Williamsbourg
,
1979
:
1
9
.
18.
Jung W.Y., A Combined Honeycomb and Solid Viscoelastic Material for Structural Damping Applications. Department of Civil, Structural & Environmental Engineering, University at Buffalo.Thrust Area 2: Seismic Retrofit of Acute Care Facilities, 2001, 41–43.
19.
Lakes
R. S.
,
High Damping Composite Materials: E_ect of Structural Hierarchy
,
Journal of Composite Materials
, vol.
36
(
3)
,
2002
,
287
297
.
20.
McCoucheon DM Machine augmented composite materials for damping purposes. Degree of master of science thesis. Texas A&M University. December 2004.
21.
Aitharaju
VR
,
Averill
RC
.
Co zig-zag kinematic displacement models for the analysis of laminated composites
.
Mech of Comp Mater and Struct
1999
;
6
(
1)
:
31
56
.
22.
Icardi
U.
Application of zig-zag theories to sandwich beams
.
Mech of Advan Mater and Struct
2003
;
10
:
77
97
.
23.
Icardi
U.
Co plate element for global/local analysis of multilayered composites, based on a 3D zig-zag model and strain energy updating
.
Int J of Mech Sc
2005
;
47
:
1561
1594
.
24.
Icardi
U.
Higher-order zig-zag model for analysis of thick composite beams with inclusion of transverse normal stress and sublaminates approximations
.
Composites: Part B
2001
;
32
:
343
354
.
25.
Icardi
U.
,
Atzori
A.
Simple, efficient mixed solid element for accurate analysis of local effects in laminated and sandwich composites
.
Advances in Engineering Software
2004
;
32
(
12)
:
843
859
.
26.
Icardi U. Co plate element based on strain energy updating and spline interpolation, for analysis of impact damage in laminated composites. Submitted to Int J Impact Engng, October 2005.
27.
Icardi
U.
Eight-noded zig-zag element for deflection and stress analysis of plates with general lay-up
.
Composites-Part B: Eng
1998
;
29b
:
435
41
.
28.
Icardi
U
,
Zardo
G.
Co plate element for delamination damage analysis, based on a zig-zag model and strain energy updating
.
Int J Impact Eng
2005
;
31
:
579
606
.
29.
Zienkiewicz OC, Taylor RL. The finite element method, Vol. 1, 4th ed, McGraw-Hill, 1994.
30.
Hoa SV, Feng W. Hybrid finite element method for stress analysis of laminated composites, Kluwer Academic Publ.,1998.
31.
Pedersen
P.
A note on design of fiber-nets for maximum stiffness
.
J. of Elasticity
2003
;
73
(
1–3)
:
127
145
.
32.
Pagano
NJ
,
Exact solutions for composite laminates in cylindrical bending
.
J Comp Mat
1969
;
3
:
398
411
.
33.
Henrych J., The Dynamics of explosion and its use, Elsevier Science Publisher 1979.
34.
Choi
Chang
,
A Model for Predicting Damage in Graphite/Epoxy Laminated Composites Resulting from Low-Velocity Point Impact
,
J Comp Mat
1992
,
26
(
14)
:
2134
2169
.
35.
Hou
,
Petrinic
,
Ruiz
,
A Delamination Criterion for Laminated Composites Under Low-Velocity Impact
,
Comp. Science and Technology
2001
,
61
:
2069
2074
.
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