Transverse strength of continuous fiber metal matrix composites

Abstract

The composite limit flow stress for transverse loading of metal matrix composites reinforced with continuous fibers is calculated using the finite element method. The focus of this work is to compare how different models for these composites influence the resulting composite flow behavior under transverse loading. Cell models with regular square and hexagonal arrangements [1] are compared with a so-called “embedded cell model” as developed by Dietrich et al. [2,3]. In the models for regularly arranged fibers, the hexagonal arrangement is seen to result in the highest limit stress for volume fractions less than about 0.42, whereas the square arrangement of fibers loaded in the direction of nearest neighbors provides greater strengthening at higher volume fractions. When the square arrangement is loaded 45° to the nearest neighbor direction, virtually no strengthening is seen. The interference of fibers with flow paths is seen to play an important role in the strengthening mechanism for these composites with regularly arranged fibers. Additionally, the influence of matrix hardening as a strengthening mechanism in these composites is seen to increase with volume fraction due to increasing fiber interaction. This is strengthening that results over and above the strengthening due to the addition of fibers. The embedded cell model is seen to agree quite well with the hexagonal model when the matrix has perfectly plastic behavior. However, when the matrix work hardens, the embedded cell model results in a higher asymptotic reference stress than calculated with the hexagonal model.