Composite-overlay reinforcement of cutouts and cracks in metal sheet

Abstract

Finite element computer programs were developed for the planform analysis and the longitudinal cross-section analysis of metal sheet reinforced by adhesively bonded overlays of composite material. The analyses articulate the separate responses of the metal sheet, the composite overlays, and the adhesive layers. All materials are assumed to be orthotropic and linear elastic, with the provision that nonlinear interlaminar shear deformation can be approximated by a series of stepwiselinear solutions. The computer programs were developed specifically for the study of three general configurations: (1) a sheet with a reinforced cutout; (2) a sheet with a reinforced cutout with two symmetrical transverse cracks, within the sheet, radiating away from the cutout edge; and (3) a sheet with a reinforced transverse crack. The programs are also suitable for the study of bonded lap joints. The principal output of the computer programs is a set of contour plots of stress and strain fields throughout the sheet, the overlays, and the adhesive layers. A series of laboratory tests was conducted to demonstrate the validity of the analyses. Strains measured on the surfaces of specimens representing the general configurations studied were, for the most part, in good agreement with strains predicted by the finite element analyses. Significant correlations between certain failure modes and the stresses computed by the finite element analyses were apparent. Similarities between the modes of failure under static and fatigue loading were also evident.

Component parts assembly with joints. Adhesive-mechanical Part 4. Analysis and test of bonded and wellbonded lap joints

“…The general approach used here parallels one used earlier for the planform analysis of composite-reinforced cutouts and cracks [2,3]. Figure 3(a) shows the network of triangular finite elements used for the analysis of the weldbonded joint shown in Figure 1 and a similar spotwelded joint.…”

“…If a change in stress results in an intersection with the single-valued stress-strain curve passing through the origin (defined by equation (2) in the first quadrant) further change in stress results in a change in strain along that curve. All linear stressstrain segments have a slope defined by the constant shear modulus G .…”

“…For each solution the adhesive shear stresses and strains throughout the joint are defined by a single-valued function such as equation (2).…”

“…The shear stress-strain relationship for the adhesive, as determined by three "napkin ring" torsion tests, is given by equation (2) and the empirical constants G , A, B, C, and t in Section 3.1.…”

Non-metallic antenna-support materials

“…This type of nonlinear analysis has been used in this laboratory to study composite-reinforced cutouts in metal sheet [5].…”