Damage detection on laminated composite materials using several NDT techniques

The aim of this study is to evaluate the features and capabilities of four different methods when utilised to detect and quantify impact damage on composite laminates subjected to low-velocity impact. Carbon fibre-reinforced epoxy composite was used and the experimental tests were performed on [0,90,0,90]_2s and [90₄,0₄]_S laminates using a drop-weight testing machine. The tests were performed with an impact energy of 3 J, corresponding to a maximum load of 3000 N. The damage in the laminates was analysed by electronic speckle pattern interferometry (ESPI), shearography, ultrasonic testing and X-radiography. All these techniques were able to detect almost all the defects, although the interferometric methods showed some limitations. X-radiography is an interesting alternative technique, but was not able to localise delaminations in the thickness direction. The ultrasonic methods, A-scan and C-scan, were shown to be the best solutions for inspecting the samples. According to the experimental results, these techniques were able to detect and measure the damage extent with great precision.