Design Analysis of the Outwater-Murphy Single-Fiber Specimen

Abstract

A design analysis of the Outwater-Murphy (OM) compression test specimen is presented. The objective is to size the dimensions of the OM specimen for interface fracture toughness testing of glass and carbon fibers in a polymer matrix. A simple fracture mechanics analysis is developed based on mechanics of materials principles assuming linear-elastic behavior of the fiber and matrix. A successful test demands fiber/matrix debonding prior to any other failure mechanisms such as net section yielding, fiber microbuckling and global buckling of the specimen. The analysis of the results indicates that the test should be viable for OM specimens with a small cross section and a small central hole. Tests on E-glass/vinylester specimens were successfully conducted providing a fiber/matrix interface toughness of 38 J/m2, in reasonable agreement with interface toughness data for similar systems determined by other test methods.