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Design of PZT Sensor Strip for Structural Health Monitoring, with added structural strength benefit for composite laminates

IP.com Disclosure Number: IPCOM000237704D
Publication Date: 2014-Jul-04
Document File: 6 page(s) / 409K

Publishing Venue

The IP.com Prior Art Database

Related People

Mudit Rastogi: INVENTOR

Abstract

Composite structures are being used in various industries increasingly. This has increased the requirements of Structural Health Monitoring solutions which are useful for diagnosing early defects by effective sensor integration in them. However, it remains a challenge to embed these sensors while maintaining the structural strength. Any modification in the material and/or geometric properties of composite structure can have negative impact on the life and maintenance of the material. Hence, there is a need for a new sensor embedding method which can monitor the structural parameters without affecting the structural integrity. The proposed design uses sensor encapsulation with thermoplastic layer and shape memory alloys. This makes the sensor design capable for integration in the composite while minimizing its influence on the structural strength and integrity of the host composite structure.

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Page 01 of 6

  Design of PZT Sensor Strip for Structural Health Monitoring, with added structural strength benefit for composite laminates

Mudit Rastogi ABSTRACT

Composite structures are being used in various industries increasingly. This has increased the requirements of Structural Health Monitoring solutions which are useful for diagnosing early defects by effective sensor integration in them. However, it remains a challenge to embed these sensors while maintaining the structural strength. Any modification in the material and/or geometric properties of composite structure can have negative impact on the life and maintenance of the material. Hence, there is a need for a new sensor embedding method which can monitor the structural parameters without affecting the structural integrity. The proposed design uses sensor encapsulation with thermoplastic layer and shape memory alloys. This makes the sensor design capable for integration in the composite while minimizing its influence on the structural strength and integrity of the host composite structure.


1. Introduction

Structural Health Monitoring (SHM) provides an alternate solution to detect defects in composites than conventional NDT methods. It also has the advantages of being less expensive and time consuming than some of the NDT methods. Hence with the increasing use of composites in a wide range of engineering applications, it has gathered huge amount of interest. One of the SHM techniques which could be integrated with composite structures is using UGW (ultrasonic guided waves) generated by PZT sensors. The proposed solution is to embed sensor(s) /sensor strip into the composites and measure the response of the sensor arrays by periodic sampling. The most commonly used method nowadays to embed PZT sensors in composites is using sensor strips made of Kapton. They are also commercially available in the market as


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"Smart Layers". However inserting any foreign object changes the micromechanics of composite which give rise to inter laminar stresses; added to this stresses poor adhesiveness between the insert surface area and composite results in separation of the adjacent material surfaces called delamination. Delamination is one of the most critical failure modes in a composite structure. The critical strain energy release rate is the widely accepted measure of total energy required to initiate a delamination and is a good measure to rank how susceptible a material is to delamination. In past, theoretical model on fracture mechanisms have emphasized on the plastic deformation around the crack tip. This was a critical factor in determining the delamination fracture toughness and the relationship between the extent of crack tip plastic zone/ damage zone and critical strain energy release rate.

There are three basic delamination modes, as shown in the Fig. 1, which can occur one at a time or in combination. These modes are Mode I, the opening mode, Mode II, sliding shear mode and Mode...