Through-the-thickness identification of impact damage in composite laminates through pulsed phase thermography

Abstract

In this paper we demonstrate through-the-thickness imaging of barely visible impact damage in a two-dimensional woven, carbon fiber epoxy laminate using pulsed phase thermography (PPT). Specifically we calibrate the defect depth with blind frequency for the particular material system using a specimen with simulated defects in the form of polymer foam inclusions. The calibrated depth versus blind frequency relation is then applied to specimens with barely visible impact damage due to low-velocity impacts. The polymer foam reproduces the irregular boundaries and thin nature of the delaminations, but does not reproduce through-the-thickness variations. The extent of delamination at different depths was reconstructed as a function of depth for varying levels of impact energy. The extent of damage imaged using PPT corresponded well with visual observations and microscopy images.

Assessment of Self-healing Efficacy of Thermoplastic Ionomer Films Interleaving Carbon-Fibre Reinforced Epoxy Matrix Laminates

“…Therefore only a single imaging measurement must be performed and the imaging time is relatively short. Of great interest is the phase image which, being related to the propagation time delay, is independent of optical or infrared surface features, besides can probe roughly twice the thickness examined by, for instance, pulse thermography images [19,20].…”

Numerical simulation of phase images and depth reconstruction in pulsed phase thermography

“…The benchmark specimen configuration chosen for this study was based on the ASTM E2582-07 standard, as experimental data was available through previous testing in our laboratory [24]. The specimen was a 125 mm × 125 mm plate of 12 layers of 2D twill, carbon-fiber reinforced epoxy (CFRP).…”

“…Values for the heat transfer coefficient calculation are given in table 2. From the experimental data in [24], immediately after the heat pulse, = T 44 s °C and at thermal equilibrium, = T 33 s °C. For both cases, Ra L ⩽ 10 9 , therefore the convection heat transfer coefficient is estimated as [28],…”

“…The properties of the original polymer foam, as seen in figure 6(a), were given by the manufacturer. When the foam was inserted into the laminated composite it was compressed 6(b) [24]. Further, it is assumed that resin entered the foam during this same period, as shown in figure 6(c).…”

Thermographic inspection of a wind turbine rotor blade segment utilizing natural conditions as excitation source, Part I: Solar excitation for detecting deep structures in GFRP

“…[16]) or CFRP (e.g. [5,24,19,28]). By using infrared radiators and flash lamps, active thermography has also been successfully applied for detecting defects in GFRP structures [3].…”