Title

Analytical Approach to Composite Behavior

Date

1969

Index Abstract

Coming Soon

Photo Quality

Complete

Report Number

AFML TR 69-129

Creator

Ebert, L. J.

Hamilton, C. H.

Hecker, S. S.

Wright, P. K.

Fedor, R. J.

Corporate Author

Case Western Reserve Univ Cleveland OH Dept Of Metallurgy

Laboratory

Air Force Materials Laboratory

Extent

310

Identifier

AD0857059

Access Rights

Export Controls

Distribution Classification

1

Contract

F33615-67-C-1487

DoD Project

None Given

DoD Task

None Given

DTIC Record Exists

No

Distribution Change Authority Correspondence

USAFML LTR

Distribution Conflict

No

Abstract

The applicability of the binary composite model has been completely generalized for any combination and arrangement of materials. This refinement has eliminated the previous restriction where only composite cylinders in which the core member would yield before the case member could be treated analytically. It was found that the residual stresses in the composite induced during cooling from fabrication temperatures needed to be analyzed and incorporated into subsequent axial loading predictions. The residual stresses, which result from dissimilar thermal expansions of the components of composites, were predicted analytically and compared to the experimentally determined values for OFHC copper core with a 4340 steel case and OFHC copper core with a maraging steel case. The effect of tensile prestrain on the residual stress states and on subsequent stress-strain behavior of binary composites and tungsten-copper filamentary composites was experimentally investigated and analytically predicted. The fabrication-induced residual stresses were sufficiently altered to cause a substantial rise in the tensile flow stress curves upon reloading. Prestrains into the elastic-plastic behavioral region were emphasized. A double concentric model was developed to assess the seriousness of the presence of an unconstrained outer surface of the models. The double concentric model can also be used to predict the behavior under axial loading of composites which contain an interaction layer or diffusion protection coating at the fiber-matrix interface. This model has been developed for both elastic and strain-hardening plastic deformation in the components of the composites. Presentation of experimental data (of double-concentric model composites) completes the verification of this approach. The elastic response of a two component composite cylinder uniformly loaded along its axis was compared analytically to a corresponding hexagonal fiber composite element. The analytical comparison of the elastic behavior of the two composite elements provided justification and identified limitations for the use of the cylindrical approximation to the hexagonal geometry for the yielding and subsequent plastic deformation of the matrix component. The comparative elastic analysis considered the micro-stress field and its effect on the composite modulus and yielding behavior. Experimental data are given for the study of end effects in prototype (50 mil tungsten wires in copper matrix) fiber composites. Composites of both 7 and 19 wires were assembled to represent loose and close packed conditions, with precut discontinuous tungsten wires being included in different numbers and geometrci configurations.

Report Availability

Full text available

Date Issued

1969-06

Provenance

Lockheed Martin Missiles & Fire Control

Type

report

Format

1 online resource