Monotonic and fatigue loading behavior of quasi-isotropic graphite/epoxy laminate embedded with piezoelectric sensor

Abstract

This study investigated the effects of embedding piezoelectric lead zirconate-titanate (PZT) sensors on the tensile strength and fatigue behavior of a quasi-isotropic graphite/epoxy laminate as well as the embedded sensor's voltage degradation under these loading conditions. For this, AS4/3501-6 laminates were fabricated with a [0/±45/90] S lay-up where PZT was inserted into a cut-out area in the two middle 90 • plies. Monotonic tensile tests showed that both the average ultimate strength and Young's modulus of the tested laminate with or without PZT were within 4% of each other. The fatigue lives with and without PZT were very close to each other as well. Overall, the sequence of damage in this study agreed with previous investigations of the damage mechanisms for [0/±45/90] S quasi-isotropic laminates. The ranges of modulus reduction in both cases, with and without PZT, were within 5 to 15% of each other during fatigue loading. Delamination growths in both cases during most of the fatigue life were also very comparable to each other. Further, this study showed that the embedded PZT would maintain a steady voltage output indefinitely when mechanically cycled within its operational strain limit. It thus appears that the embedment of PZTs in a cut-out area of 90 • plies of quasi-isotropic graphite/epoxy laminates would not affect their monotonic tensile and fatigue behavior.

Mechanical and vibration testing of carbon fiber composite material with embedded piezoelectric sensors

“…Bronowicki et al 6 tested monolithic Navy type I and II lead zirconate titanate (PZT) elements embedded in composite specimens, looking at tension, compression, temperature, and fatigue effects. They measured the piezoelectric properties throughout testing, showing the degradation with tensile strain up to 4000x10 -6 m/m, and with temperature cycling of -100 to +100 o C. Mall et al 7,8 tested monolithic piezoelectric elements embedded in composite specimens, looking at sensor voltage output under tensile and fatigue tests, and fatigue testing of the piezoelectric element when used as an actuator. They found that the tensile strength and Young's modulus with and without PZT were within 4% of each other.…”

Onset of Resin Micro-cracks in Unidirectional Glass Fiber Laminates with Integrated SHM Sensors: Numerical Analysis

“…A number of experimental studies [1][2][3][4][5][6] have been conducted to assess the strength and failure modes of composite materials with embedded devices such as silicon chips, piezoelectric (PZT) sensors, or fiber-optic sensors (FO). From these studies it appears that in cases where the thickness of the inclusion does not alter significantly the through-the-thickness geometry of the host material, the resulting stress concentration is rather small, and thus has negligible effects on the material integrity.…”

Structural integrity of composite laminates with embedded micro-sensors

“…Experimental studies [1][2][3][4][5][6] have been conducted on the strength and failure of composite materials with embedded devices such as silicon chips, PZT sensors, or fiber optic sensors, etc. From these references it appears that in cases where the thickness of the inclusion did not alter significantly the through-the-thickness geometry of the host material, the local stress concentration values remained very small thus negligible effects on the material integrity were observed.…”