Experimental and theoretical study on piezoresistive properties of a structural resin reinforced with carbon nanotubes for strain sensing and damage monitoring

Abstract

The development of embedded sensors based on a structural thermosetting epoxy resin reinforced with 0.3 wt% of multi-walled (MW) carbon nanotubes (CNTs) for real-time structural health monitoring is presented. The storage modulus of the composites is higher than 2000 MPa in a wide temperature range confirming their reliability as structural parts, especially for aeronautical applications. The piezoresistive properties are studied on specimens subjected to both tension and flexural stresses. The yield strength evaluated with the same approach adopted for metallic materials and alloys compares successfully with the information provided by the electrical characterization. Different levels of damages are revealed by the changes in the piezoresistive properties due to the morphological modifications in the conductive network of CNTs within the resin. The analysis of an empirical law is proposed for predicting the strain-dependence of the electrical and mechanical properties of material when the samples are subjected to stretch-release cycles. The average CNTs interparticle distances as function of bending is also estimated.

Damage Monitoring of Structural Resins Loaded with Carbon Fillers: Experimental and Theoretical Study

“…With the recent advent of nanotechnology science, carbon nanofillers have been used for the development of multifunctional nanocomposites with integrated self-sensing properties. Based on these nanocomposites, SHM devices able to detect damage in structural materials can be produced [2][3][4][5][6][7][8]. More specifically, the inclusion of electrically conductive nanofillers in epoxy resins characterized by mechanical performances suitable for fulfilling structural requirements confers them piezoresistive properties.…”

Experimental characterization of the quasi-static and dynamic piezoresistive behavior of multi-walled carbon nanotubes/elastomer composites

“…Carbon nanotube (CNT) elastomer composites have attracted scientific interest because of their high compliance and their significantly improved electrical properties. [1][2][3][4] CNT can form a continuous conductive network inside elastomers even at a very low weight fraction, characterized by a sharp increase in the electrical conductivity and well known as the percolation threshold. The percolation threshold corresponds to the CNT volume fraction at which the composite exhibits a structured three-dimensional (3D) network and it is moved from an electrically insulative state to an electrically conductive state.…”

Evaluation of Different Non-destructive Testing Methods to Detect Imperfections in Unidirectional Carbon Fiber Composite Ropes

“…Moreover, matrix and interface damage, such as microcracking, delamination, environmental aging and debonding, does not cause an increase in strain although it can reduce the strength and service life of a rope [10]. Matrix cracking could be observed using electromagnetic methods if the matrix is made conductive by adding carbon nanotubes [11]. Like embedded sensors, this approach may be difficult to implement into existing products and production lines.…”

“…The TSA analysis is one typical method applied to polymer composites, including carbon fiber reinforced plastic (CFRP), to detect different kinds of damage, but most sensitive to delaminations [12][13][14]. The reflection or transmission of ultrasonic waves can be used to detect interfaces or heterogeneities in CFRP components [11]. The principle of ultrasonic inspection is similar to the thermal waves of the TSA phase image and is therefore especially sensitive to delaminations [11].…”

“…The reflection or transmission of ultrasonic waves can be used to detect interfaces or heterogeneities in CFRP components [11]. The principle of ultrasonic inspection is similar to the thermal waves of the TSA phase image and is therefore especially sensitive to delaminations [11]. Eddy current testing [15] is typically used for inspecting undulations in carbon fiber reinforcement fabrics, quality control of stacking sequence, fiber orientation and curing effects [16].…”