Out-Of-Plane Permeability Evaluation of Carbon Fiber Preforms by Ultrasonic Wave Propagation

Abstract

Out-of-plane permeability of reinforcement preforms is of crucial importance in the infusion of large and thick composite panels, but so far, there are no standard experimental methods for its determination. In this work, an experimental set-up for the measurement of unsaturated through thickness permeability based on the ultrasonic wave propagation in pulse echo mode is presented. A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the through thickness flow front during a vacuum assisted resin infusion experiment. The set-up was tested on three thick carbon fiber preforms, obtained by stacking thermal bonding of balanced or unidirectional plies either by automated fiber placement either by hand lay-up of unidirectional plies. The ultrasonic data were used to calculate unsaturated out-of-plane permeability using Darcy’s law. The permeability results were compared with saturated out-of-plane permeability, determined by a traditional gravimetric method, and validated by some analytical models. The results demonstrated the feasibility and potential of the proposed set-up for permeability measurements thanks to its noninvasive character and the one-side access.

Experimental and Numerical Study of Vacuum Resin Infusion of Stiffened Carbon Fiber Reinforced Panels

“…The experimental setup for the measurement of out of plane, non-saturated, permeability by ultrasonic wave propagation in pulse echo mode is sketched in Figure 3 [28]. A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the Polyethylene glycol 400 (PEG400), provided by Sigma-Aldrich (Milano, Italy), was used as a test fluid.…”

“…A single ultrasonic transducer, working both as emitter and receiver of ultrasonic waves, was used to monitor the Polyethylene glycol 400 (PEG400), provided by Sigma-Aldrich (Milano, Italy), was used as a test fluid. Its viscosity was measured at 25 • C in a parallel plate ARES rheometer (Rheometric Scientific, Piscataway, NJ, USA) with a 50 mm plate diameter in order to obtain a fluid at room temperature characterized by the same viscosity of the PRISM resin at the infusion temperatures, which is in the range of 0.06-0.1 Pa•s [28]. The measurement of in-plane permeability was performed during a Vacuum-Assisted Resin Infusion (VARI) process.…”

“…Often, a multi-layer fiber preform is used, composed of several different layers whose orientation and stacking sequence should optimize the mechanical performance. Different measurement methods are available in the literature, mostly related to the in-plane permeability, but there is not yet a standard procedure [27,28] and the data, obtained using different methods and different fabric architecture, are often not consistent [29]. Very few studies are reported on out-of-plane permeability, which is more difficult to measure [30,31].…”

Carbon Fiber Reinforced Polymers

“…Challenges in composite manufacturing can only be faced with a correct process design. Lionetto et al [ 12 ] presented an experimentally validated model to simulate the resin infusion process of an aeronautical component by accounting for the chemo-physical and rheological changes in the crosslinking resin and the measurement of the in-plane and out-of-plane permeability of the reinforcement with an in-house-built ultrasonic set-up [ 13 ]. The numerical simulation of the resin infusion process involved modeling of the resin flow through the reinforcement, heat exchange in the part and within the mold and the crosslinking reaction of the resin.…”

Ultrasound for Material Characterization and Processing

“…Lionetto et al [ 10 ] in the paper entitled “ Out-of-plane permeability evaluation of carbon fiber preforms by ultrasonic wave propagation ” present a novel experimental set-up, based on ultrasonic wave propagation, for the determination of the out-of-plane permeability of carbon fiber reinforcements, which is the dominant property in the infusion of large and flat panels with a high thickness. An accurate characterization of the reinforcement permeability is fundamental in order to estimate the optimum process parameters for manufacturing high-quality components.…”