Characterization of CFRP Using Laser Vibrometry

Abstract

The investigation was focused on Carbon Fibre Reinforced Polymers (CFRP). In the first part of research the aim was the characterization of CFRP surfaces. These surfaces were influenced by release agent, hydraulic fluid, moisture and overheating. In the second part of research adhesive bond quality was investigated. Three different cases of possible weak bonds were focused on. Weak bond caused by release agent contamination, moisture contamination and poor curing of adhesive. The characterization was conducted using laser vibrometry used as NDT tools. An active element in the form of piezoelectric transducer was used to excite the samples made out of CFRP material. Laser vibroemter was used to register the surface response. Combining the piezoelectric excitation with laser sensing a tool was obtained to measure precisely the propagating elastic waves. The excited waves were measured in defined points by the vibrometer obtaining the wavefield. In order to characterize the surface and bonding quality an indicator was proposed based on propagating wave parameters. The guided elastic wave velocity depends material properties (Young modulus, density, Poisson ratio) and thickness of the sample. It was assumed that comparison of the velocities can provide an information about the bond condition. All the investigated scenarios showed deviation from the reference case.

Numerical modeling of laser-induced shock experiments for the development of the adhesion test for bonded composite materials

“…For elements of context, see [1][2][3]. Selected ENCOMB results are given in [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The first step is to control adherent surfaces by inspecting the parts before bonding process.…”

“…Different under-development techniques address this issue. For examples, guided waves, monitored by a laser-scanning vibrometer, have shown good sensitivity to water contamination [9]. Electromechanical impedance measurements have shown the technique potential to reveal the presence of release agent or moisture, as well as poor curing [10,11].…”