A Time-domain Reflectometry Method for Automated Measurement of Crack Propagation in Composites during Mode I DCB Testing

Abstract

This article describes a new technique for automated measurement of crack initiation, growth, and propagation in composite materials during mode I double cantilever beam (DCB) testing. The proposed method uses time-domain reflectometry (TDR) to detect changes in geometry and electromagnetic properties (dielectric or magnetic) along a transmission line that can be embedded in or bonded to the surface of the specimen. Two types of transmission line TDR sensors are evaluated (IM7 carbon fiber and ARACON) during DCB tests. A P-SPICE transmission-line simulation model is used to verify the baseline signal response for the DCB sensor and the sensitivity for crack detection, with good agreement. Comparison with standard visual methods in DCB testing showed excellent correlation in crack location, crack propagation (LC), and the interlaminar fracture toughness (GIC) values. The TDR sensor design and model-based parametric studies are carried out to determine optimal sensor geometry and configuration. The results demonstrate that the TDR-based method can measure crack propagation parameters at high resolution and accuracy, in an automated manner using low-cost sensors.

Monitoring the production of FRP composites: A review of in-line sensing methods

“…The method shows potential in in-line monitoring [22][23][24], damage detection [71][72][73] and self-sensing [73,25]. Moreover, it is the only method able to detect both electric and magnetic properties.…”

Electric Time Domain Reflectometry Sensors for Non-Invasive Structural Health Monitoring of Glass Fiber Composites

“…A good geometrical design must ensure that there are uniform electromagnetic fields inside the system under observation. Obaid et al [17] used two parallel wires embedded inside the specimen for double cantilevered beam (DCB) measurements (( Figure 3(a)). This is a good configuration for DCB testing, where the location on cracks is known before hand and is in between the transmission lines.…”

“…In composite applications, TDR has been successfully implemented for flow and cure monitoring in liquid composite molding processing [15,16]. Double cantilevered beam testing of composite specimens has been successfully reported in literature [17]. With recent advances in microwave engineering and with the advent of picoseconds rise time and gigahertz frequency pulses, TDR has been used to probe much smaller structures.…”

Impact damage detection of a carbon-fibre-reinforced-polymer plate employing self-sensing time-domain reflectometry

“…Several works have used time-domain reflectometry (TDR) to detect damage [12][13][14]. The authors of the present paper have developed self-sensing TDR for the detection of fibre breakages using a parallel plate [15] and using a micro-strip line (MSL) [16].…”