An experimental study on multiwalled carbon nanotube nanocomposite piezoresistivity considering the filler agglomeration effects

Piezoresistive strain sensing of multiwalled carbon nanotube (CNT)-reinforced polymer nanocomposites considering the effect of agglomeration is experimentally investigated. Thermoplastic polyurethane is used as composite matrix with melt mixing method for fabricating the nanocomposite. The electrical resistance of the nanocomposite specimens is measured by a designed electrical circuit in conductivity and piezoresistivity tests. The electrical resistance of the nanocomposite decreases by a nonlinear relation when CNT is added up to 1.5 wt% and has an inverse behavior after this weight fraction. Comparison between scanning electron microscope images of the nanocomposite specimen fracture surfaces shows that the CNT agglomeration is the reason for decreasing the nanocomposite electrical properties. Also, decrease of the mechanical properties of the nanocomposite in higher filler content than 1.5 wt%, confirms the agglomeration effects. In addition, it is illustrated that the CNT agglomeration decreases strain sensing in the nanocomposite. Moreover, different piezoresistive behaviors of the nanocomposite in low and large strains are explained, according to the piezoresistivity mechanisms. Change of the piezoresistivity mechanism type, causes a nonlinear growth of the nanocomposite electrical resistance, in large strain.