Carbon nanotube sensor thread for distributed strain and damage monitoring on IM7/977-3 composites

Abstract

Laminated composite materials are used in applications where light weight is a key requirement. However, minor delamination damage in composites can propagate and lead to the failure of components. Failure occurs because delamination reduces the local bending stiffness and increases bending stress, which leads to the propagation of damage and eventual failure. These failures may be avoided if the damage could be detected early and repaired. Although many damage detection methods have been investigated, none are in widespread use today to prevent the failure of composites. This paper describes the use of carbon nanotube sensor thread to monitor strain and damage in composite materials. Sensor thread was bonded onto an IM7laminated composite coupon to measure surface strain in a quasi-static uniaxial tensile test. The sensor thread was calibrated against a strain gage, which was also mounted to the coupon. The sensor thread measured the average strain over the length of the sample and indicated when the strain exceeded a nominal safe level. Sensor thread was also bonded to the surface of laminated composite panels in different patterns and detected, located and partially characterized the damage caused by multiple impacts to the panel. The new findings in this paper can be summarized as; (1) carbon nanotube sensor thread was tested as a distributed sensor for the first time on IM7/977-3 composites; (2) the sensor thread was found to monitor strain and detect damage in the composites with a potential sensitivity down to the micro-crack level; (3) the sensor thread was barely visible on the composite and did not add significant mass or affect the integrity of the composite; (4) the data acquisition system developed was simple and reliable.

The use of carbon nanotubes for damage sensing and structural health monitoring in laminated composites: a review

“…After the initial idea of using CNTs as multifunctional sensors for FRPs, 23,24,27 numerous studies based on GF/CNT (or CF/CNT) hybrid multi-scale composites have been conducted [44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60] to further explore the potential of CNT damage sensing methodologies in laminated composites. It is well established that damage in composite laminates starts from matrix-dominated failure modes such as matrix cracking and delamination, followed by fiber breakage which normally occurs near the end of the composites' lifetime.…”

Plastic and transformation interactions of pores in shape memory alloy plates

“…This investigation provides a good understanding of the design and optimization of porous SMA structures. However, localized plasticity was neglected in this model, which is important [19][20][21][22] even at low macroscopic loads due to stress localization near and between the pores [18,23,24]. Therefore, in this study, a combination of plasticity and reorientation is used to guide the design and optimization of SMA foams based on a model that incorporates orientation, reorientation, and plasticity.…”

Foil Strain Gauges Using Piezoresistive Carbon Nanotube Yarn: Fabrication and Calibration

“…Carbon nanotube (CNT) yarns are micro-scale fibers that contain thousands of intertwined carbon nanotubes in their cross sections and exhibit piezoresistance characteristics that can be tapped for sensing strain [ 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. The use of strain gauge sensors comprising CNT yarn may offer a feasible and practical way to measure strain inside polymeric and composite materials [ 61 , 62 , 63 , 64 ], and on the surface of all materials [ 65 ]. The work presented in this paper focuses on foil strain gauge sensors that could be adhered to external surfaces.…”