Mechanical Properties of Matrices and Micro-mechanics of Discontinuous Fiber Composite Alloys

Abstract

The effects of elasticity, strength and work hardening of matrices on micro-mechanics of discontinuous fiber composite alloys were investigated by means of the Moiré pattern technique. Pb-5% Sn alloy containing a short stainless steel fiber and pure Ni containing a short W fiber were studied as the two-dimentional models of the discontinuous fiber composite alloys. Uniaxial tensile loading which was parallel to the fiber was considered. The following results were obtained:
(1) The shear strains in the matrix along the fiber-matrix interface of stainless steel/Pb-5% Sn were larger than that of W/Ni under almost the same maximum value of fiber strain. And, in both cases, the maximum shear strains in the matrix along the fiber-matrix interface were over the yield shear strains of the each matrix even at a little loading to the composite.
(2) Stress distribution in a discontinuous fiber almost agreed with Kelly-Tyson’s equaition and Piggott’s equation. But, it did not agree with Piggott’s assumptions, because the maximum shear strain in the matrix was over the yield shear strain of the matrix in the entire region.
(3) The larger the maximum value of fiber strain e_f max, the higher the shear strain concentration factor τ_m max⁄e_f max at the fiber-matrix interfaces. The concentration factor of stainless steel/Pb-5% Sn was larger than that of W/Ni in the entire region.
(4) Because of the high strain concentration in the matrix at the end of the fiber, the failure of stainless steel/Pb-5%Sn originated in fracture of the matrix around the end of the fiber and pulling-out of the fiber from the matrix. On the other hand, W/Ni having a relatively low strain concentration failed due to fracture of the matrix which was adjacent to W fiber fracture points.