A Cracked Orthotropic Sheet Stiffened by a Semi-Infinite Orthotropic Sheet

The stress-intensity factor is determined for a cracked orthotropic sheet adhesively bonded to an orthotropic stringer. Since the stringer is modeled as a semi-infinite sheet, the solution is most appropriate for a crack tip located near a stringer edge. Both adherends are treated as homogeneous, or...

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Bibliographic Details
Main Author: Bigelow, C. A
Format: Report
Language:English
Subjects:
ADHESION
ADHESIVE BONDING
AEROSPACE CRAFT
CRACK TIPS
CRACKING(FRACTURING)
CRACKS
DAMAGE ASSESSMENT
DISPLACEMENT
ELASTIC PROPERTIES
EPOXY LAMINATES
FIBER REINFORCED COMPOSITES
FLEXIBLE STRUCTURES
GRAPHITE EPOXY COMPOSITES
GREENS FUNCTIONS
INTEGRAL EQUATIONS
Laminates and Composite Materials
Mechanics
MODULUS OF ELASTICITY
POISSON RATIO
SHEAR STRESSES
STIFFENING
STIFFNESS
STRESS CONCENTRATION
STRINGERS
TOLERANCES(MECHANICS)
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Summary:The stress-intensity factor is determined for a cracked orthotropic sheet adhesively bonded to an orthotropic stringer. Since the stringer is modeled as a semi-infinite sheet, the solution is most appropriate for a crack tip located near a stringer edge. Both adherends are treated as homogeneous, orthotropic media. It is assumed they are in plane stress and the adhesive is in pure shear. From Green's functions and the complex variable theory of orthotropic elasticity developed by Lekhnitskii, a set of integral equations is obtained. The integral equations are replaced by an equivalent set of algebraic equations, which is solved to obtain the shear-stress distribution in the adhesive layer. With these stresses, equations for the stress-intensity factors at both crack tips are found. A parametric study is conducted to determine the sensitivity of the system to material properties and specimen configuration. Unless the crack tip is very close to or under the stringer, the stress-intensity factor is approximately that of an unstiffened sheet. However, as the crack propagates beneath the stringer, the stress-intensity factor decreases significantly. Increasing the stiffness of the stringer or the adhesive also results in a decrease in the stress-intensity factor. (MM)