Vibro-acoustic modulation measurements for a lifetime evaluation of composite materials

This paper investigates the influence of different damage types and their interaction on the vibroacoustic behaviour of glass fibre and carbon fibre reinforced polymers (GFRP and CFRP) under stepwise tensile and fatigue loading. For this purpose, different GFRP layups were used to correlate visible matrix cracks with VAM signal. Additionally, for CFRP the layer thicknesses are varied for cross-ply laminates with constant areal fibre weight (268 g/m2) and quasi-isotropic laminates with different areal fibre weights (30, 60 and 120 g/m2). After damage introduction under tension-tension loading (R=0.1), high-frequency Lamb waves are introduced via bonded piezo ceramic actuator and modulated by a low-frequency longitudinal wave using a servo-hydraulic testing machine. In this study, the analysis and interpretation of the vibro-acoustic response signal can be used to demonstrably identify different damage types and conditions of the CFRP specimens. The sideband amplitudes and the modulation index are used as VAM characteristics in the frequency domain and the shape of the modulation envelope in time domain as well as X-ray scans to prove the damage progress after various cycles. It is shown that regardless of the lay-up, both inter-fibre failures, as well as extensive delaminations, can be reliably and sensitively detected using a simple vibration-based test setup, providing a promising nondestructive testing methodology. Finally, it is demonstrated that for certain GFRP specimens the modulation index and lifetime can be predicted after only a few loading cycles.

Subjects

Damage progression

Fiber reinforced composites

Health monitoring

Non-destructive testing

Vibro-acoustic modulation

DDC Class

620: Engineering

660: Chemistry; Chemical Engineering

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Vibro-acoustic modulation measurements for a lifetime evaluation of composite materials