Free-Edge Interlaminar Stresses in Angle-Ply Laminates: A Family of Analytic Solutions

2016 ◽  
Vol 83 (5) ◽  
Author(s):  
Johnathan Goodsell ◽  
R. Byron Pipes
Keyword(s):  
Uniaxial Extension ◽  
Free Edge ◽  
Analytic Solutions ◽  
Thermomechanical Loading ◽  
Interlaminar Stresses ◽  
The Family ◽  
Stress Components ◽  
Complete Set ◽  
Interlaminar Shear ◽  
Angle Ply Laminates

A family of analytic solutions for the prediction of interlaminar stresses in angle-ply laminates has been developed and is presented in a unified form and as a unique set of solutions. The uniqueness of the formulation is demonstrated for the class of thermomechanical states of deformation for which the solutions are valid. These are shown to be limited to the specific cases wherein only two in-plane stress components and one interlaminar stress components are nonzero. Interlaminar shear stress in the angle-ply laminate subjected to thermomechanical loading conditions of uniaxial extension, uniform temperature change, and anticlastic bending is shown to make up the family of solutions in the unified formulation. Further, these are shown to comprise the complete set of the solutions and the conditions which control the limitations of this family of solutions are articulated.

Free Edge Stresses in Elastic and Viscoelastic Composites Under Uniaxial Extension, Bending, and Twisting Loadings

1997 ◽  
Vol 119 (3) ◽  
pp. 266-272 ◽  
Author(s):  
Sung Yi ◽  
H. H. Hilton
Keyword(s):  
Stress Relaxation ◽  
Constitutive Relations ◽  
Plane Deformation ◽  
Uniaxial Extension ◽  
Free Edge ◽  
Time Dependent ◽  
Interlaminar Stresses ◽  
Shear Moduli ◽  
Deformation State ◽  
Interlaminar Shear

Time-dependent interlaminar stresses in elastic and viscoelastic laminated composites subjected to arbitrary combinations of axial extension, bending and/or twisting loads are obtained based on integral constitutive relations and Pipes and Pagano’s displacement field for laminates under a generalized plane deformation state. Numerical results obtained from the present formulation are compared against experimental data and excellent agreement within two percent was obtained between these results. Time-dependent interlaminar stresses for cross-ply and angle-ply laminates subjected to uniaxial extension, bending and twisting are also presented. Appreciable stress relaxation occurred during the loading period resulting in decreased magnitudes of residual stresses. It is seen that the rate of interlaminar shear stress relaxation is greater than the normal one, since the relaxation of shear moduli is larger than that of the normal moduli.

scholarly journals Investigation of the Free Edge Interlaminar Stresses Dependence on the PLY Thickness and Orientation

2006 ◽  
Vol 15 (1) ◽  
pp. 096369350601500
Author(s):  
Dionisios T. G. Katerelos
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Composite Laminates ◽  
Free Edge ◽  
Thermomechanical Loading ◽  
Interlaminar Stresses ◽  
Element Analysis ◽  
3 Dimensional ◽  
Out Of Plane ◽  
Dimensional Finite Element

Among the principal damage modes in composite laminates, is delamination. Design details, such as free, straight or curved, edges, induce large local out-of-plane loads, generating interlaminar stresses. In the present work, the effect of ply thickness and the angle between two adjacent layers on the interlaminar stresses developed at the vicinity of straight and curved free edges in composite laminates under thermomechanical loading is examined. The results are obtained by the application of a 3-dimensional Finite Element Analysis.

Delamination of Laminates Governed by Free Edge Interlaminar Stresses Using Interface Element

2008 ◽  
Vol 385-387 ◽  
pp. 821-824 ◽  
Author(s):  
Hossein Hosseini-Toudeshky ◽  
Meisam Jalalvand ◽  
Bijan Mohammadi
Keyword(s):  
Free Edge ◽  
Constitutive Law ◽  
Interface Element ◽  
Shear Stresses ◽  
Interlaminar Stresses ◽  
Finite Element Program ◽  
Element Program ◽  
Failure Loads ◽  
The Difference ◽  
Interlaminar Shear

In this paper, interface element with de-cohesive constitutive law is used to predict the delamination progress of laminates in which delamination is the prominent failure mode. For this purpose, a finite element program is developed to perform nonlinear damage analysis. The analyses are carried out based on the interlaminar constitutive law of elastic-plastic-damage proposed before in the literature. Delamination initiation and propagation of several laminates with dominant interlaminar shear stresses at free edges are investigated to find the failure load. It is shown that the difference between the predicted failure loads using the present study and the experimental results are 3.1% to 19.4% for various laminates.

Multiscale analysis of interlaminar stresses near a free-edge in a [±45/0/90]s laminate

2019 ◽  
Vol 54 (13) ◽  
pp. 1627-1638
Author(s):  
M Keith Ballard ◽  
John D Whitcomb
Keyword(s):  
Normal Stress ◽  
Homogeneous Model ◽  
Uniaxial Extension ◽  
Local Stress ◽  
Multiscale Model ◽  
Free Edge ◽  
Complex Stress ◽  
Computational Effort ◽  
Interlaminar Stresses ◽  
Local Stress State

A multiscale model for a [±45/0/90]s tape laminate under uniaxial extension was used to investigate the effect of modeling the heterogeneous microstructure near a free-edge. A random fiber arrangement was used for the 0° and 90° plies and homogenized properties for the 45° and −45° plies. The predicted interlaminar normal stress was compared to the prediction using a classical homogeneous model. When fibers and matrix were modeled discretely, the local stress state was shown to be sensitive to the proximity of fibers, which caused a complex stress distribution along the 0–90 ply interface. Next, the effect of reducing the size of region modeled at the microscale was investigated, since this would significantly reduce the computational effort. Reducing the region modeled at the microscale in the direction normal to the 0–90 ply interface to a size that was 25% and 10% of the ply thickness only changed the peak stresses by 3% and 8%, respectively. Reducing the microscale region in the direction normal to the free-edge to be one and two ply thicknesses in size did not have a significant effect on the predicted interlaminar normal stress at points within 75% of a ply thickness of the free-edge.

Reduction of Free-Edge Stress Concentration

1985 ◽  
Vol 52 (4) ◽  
pp. 801-805 ◽  
Author(s):  
P. R. Heyliger ◽  
J. N. Reddy
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Free Edge ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Interlaminar Shear ◽  
Three Dimensional Elasticity

A quasi-three dimensional elasticity formulation and associated finite element model for the stress analysis of symmetric laminates with free-edge cap reinforcement are described. Numerical results are presented to show the effect of the reinforcement on the reduction of free-edge stresses. It is observed that the interlaminar normal stresses are reduced considerably more than the interlaminar shear stresses due to the free-edge reinforcement.

Damage Control in Composite Laminates

2001 ◽  
Author(s):  
Alexander P. Suvorov ◽  
George J. Dvorak
Keyword(s):  
Composite Laminates ◽  
Composite Laminate ◽  
Damage Control ◽  
Thermomechanical Loading ◽  
Interlaminar Stresses ◽  
Damage Resistance ◽  
Viscoelastic Composite ◽  
Mechanical Loads ◽  
Composite Damage ◽  
The Matrix

Abstract Several effects that fiber prestress may have on stress redistribution in the plies of composite laminates and in the phases of individual plies are illustrated. These include improvement of composite damage resistance under tensile mechanical loads, reduction/cancelation of interlaminar stresses at free edges of composite laminate subjected to thermomechanical loading, and stress relaxation in the matrix phase of viscoelastic composite laminates. Specific results are found for quasi-isotropic and cross-ply symmetric S-glass/epoxy and carbon/epoxy AS4/EPON 828 laminates.

Fundamentals of Residual Stresses in Joints Between Dissimilar Materials

MRS Bulletin ◽  
1995 ◽  
Vol 20 (1) ◽  
pp. 37-39 ◽  
Author(s):  
B.H. Rabin ◽  
R.L. Williamson ◽  
S. Suresh
Keyword(s):  
Residual Stresses ◽  
Material Properties ◽  
Critical Stress ◽  
Failure Mechanisms ◽  
Dissimilar Materials ◽  
Free Edge ◽  
Structural Components ◽  
Failure Characteristics ◽  
Stress Components ◽  
Metal Joint

When a discontinuity in material properties exists across a bonded interface, stresses are generated as a result of any thermal or mechanical loading. These stresses significantly affect strength and failure characteristics and may be large enough to prevent successful fabrication of a reliable joint. The use of an interlayer material to successfully reduce mismatch stresses, thereby preventing joint failure or improving joint strength and reliability, requires knowledge of failure mechanisms and of the effects of interlayer properties on the critical stress components.The origin of residual stresses developed during cooling of a ceramic-metal joint from an elevated fabrication temperature is illustrated qualitatively in Figure 1. Away from edges, the in-plane (parallel to interface) stresses are typically compressive in the ceramic and tensile in the metal. These stresses can cause cracking perpendicular to the interface, leading to spalling or delamination failures. Such failures are frequently observed in thin-film and coating geometries. Where the interface intersects a free edge, large shear and axial (perpendicular to the interface) stresses are generated. The edge stresses are typically tensile within the ceramic and tend to promote crack propagation within the ceramic parallel and adjacent to the interface. This is the most commonly observed failure mode in bonded structural components.

The Effects of Adhesive Nonlinearity on Thermal Stress in Layered Components

1994 ◽  
Vol 116 (2) ◽  
pp. 105-109 ◽  
Author(s):  
Wan-Lee Yin ◽  
James L. Dale
Keyword(s):  
Thermal Stress ◽  
Middle Layer ◽  
Free Edge ◽  
Boundary Region ◽  
Local Concentration ◽  
Interlaminar Stresses ◽  
Softening Behavior ◽  
Stress Strain Relation ◽  
Inelastic Material ◽  
Stress Functions

Interlaminar stresses near the free edge of a multi-layered structure under thermal and mechanical loads are significantly affected by nonlinear and inelastic material properties. Most previous studies of the subject ignored such effects and obtained singular or extremely severe and localized stress fields in boundary regions based strictly on the assumption of linearly elastic stress-strain relation. In the present paper, a variational method, using approximate stress functions and the principle of complementary energy, is developed to study the thermal stress in a three-layer beam including a thin, compliant, non-linearly elastic middle layer. It is found that the elastic softening behavior of the thin layer results in dispersion of the interlaminar stresses and widening of the boundary region. Hence the use of toughened, compliant bonding layers may produce a beneficial effect by alleviating local concentration of interlaminar stresses.

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