Combining digital image correlation and phased-array ultrasonics for non-destructive testing of translaminar fracture in composite laminates

Abstract

A simple and efficient non-destructive testing method is presented to quantify translaminar fracture properties in quasi-isotropic [90/45/0/-45]3s T800SC/3900-2B carbon fibre-reinforced polymer laminates subjected to Over-height Compact Tension (OCT) and Compact Compression (CC) fracture tests. The combination of Digital Image Correlation (DIC) with phased-array ultrasonics enables the consistent measurement of the fibre-dominant translaminar crack length, damage height and hence damage resistance curves as well as the continuous monitoring of the Fracture Process Zone (FPZ). The length of the FPZ is determined by overlaying regions of saturated (fully developed) fibre damage obtained from DIC and ultrasonic C-scans. The analysis of the progressive fracture tests reveals average laminate fracture energies of 161 kJ/m2 and 68 kJ/m2 and FPZ lengths of up to 8–12 mm and 10 mm in tension and compression, respectively. It is shown that the proposed method works best when fibre-dominated damage is confined to a narrow band normal to the loading direction as observed in CC tests. In contrast, OCT test results show that delamination and the corresponding isolated ply behaviour can alter the DIC analyses and hence complicate the measurement of translaminar fracture properties.