Accession Number:

ADA164838

Title:

Composite Strengthening.

Descriptive Note:

Annual rept.,

Corporate Author:

MARYLAND UNIV COLLEGE PARK ENGINEERING MATERIALS GROUP

Personal Author(s):

Report Date:

1985-01-01

Pagination or Media Count:

116.0

Abstract:

It has been demonstrated that a strong interfacial bond is required to produce the observed strengthening in discontinuous SiCAl composites. Dislocation generation which is the strengthening mechanism is dependent upon a good bond existing between the Silicon Carbide SiC and the Aluminum AL matrix. Although it has been shown that the stresses developed in the matrix as a result of the differences in the coefficients of thermal expansion between SiC and Al are greatly reduced by the motion and generation of dislocations, an elastic residual stress can still remain. An investigation was undertaken and it was determined that the discontinuous SiCAl composites a tensile-elastic-residual stress remains in the matrix. This determination is based on results from a theoretical model, tensile and compression testing and X-ray measurements. The results from all the tests and the model are in agreement. The magnitude of the residual stress is small, e.g., with 20 V whisker in an annealed 6061 aluminum alloy matrix, the residual stress in 70 MPa. If the matrix is annealed 1100 Al, then residual stress is still smaller 43 MPa. The tensile residual stress produces a Bauschinger Effect BE which is highly dependent upon the initial direction of loading. If the initial direction of loading is in tension, the BE is small, if the initial direction of loading is in compression, the BE is very large. It has been observed that as the strength of the matrix increases, e.g., due to alloying or age hardening, the percentage increase in yield or ultimate tensile strength decreases for a given volume per cent SiCAl composite.

Subject Categories:

  • Laminates and Composite Materials

Distribution Statement:

APPROVED FOR PUBLIC RELEASE