Eigenspannung im mit gasdruckunterstütztem Feingussverfahren hergestellten langfaserverstärkten Aluminium‐Matrix‐Verbundwerkstoff

Abstract

The residual stresses between matrix und fibres in the continuous c-Al 2 O 3 fibre reinforced aluminium alloy (AlZn6Mg1Ag1) matrix composites prepared by modified investment casting were measured with x-ray diffraction as well as simulated with FEM. It was indicated as expected that tensile residual stress exists in the Matrix und compressive residual in the fibre. The average value of the residual stress in both matrix and fibre in the composites is not very significant. However it is distributed very unevenly. Next to the interface between matrix and fibre there is a small zone in the matrix with relative great tensile residual stress. The effect of fibre volume percentage on the residual stress in the composite was also analysed. With increase of the fibre volume percentage the tensile residual stress in the matrix increases while the compressive residual stress in the fibre decreases. If the fibre volume percentage in the composite exceeds 65 %, the maximal tensile residual stress will reach the yield stress of the matrix alloy and local plastic deformation will occur.

Residual Stresses in Locally Long Fiber Reinforced Aluminum Parts

“…However the measured properties of the long fiber reinforced aluminum composites are obviously lower than the theoretically calculated values, although the reinforcing fibers are not damaged during manufactures and have still the original strength. This phenomenon was reported in many researches and was mainly ascribed to the residual stresses and behaviors of the boundaries between the reinforcing fiber and aluminum matrix [3,4]. Due to the very different thermal expansion coefficients the residual stresses occur between fiber and matrix during cooling period from casting to room temperature in long fiber reinforced aluminum parts and can sometimes reach a dangerous level.…”