Multi-functional polymer nancomposites reinforced with carbon nano-fillers including graphene, graphene nanoplatelets, carbon nanotubes and carbon nanofibers are prepared for strain sensing applications. Polyurethane is selected as matrix for large strain applications due to its excellent elastic properties, while natural rubber matrix pretreated with carbon black is used for heavy duty small stain application attributed to its strong mechanical properties. The polyurethane nanocomposites are synthesized via a surface-initiatedpolymerization (SIP) method and the natural rubber nanocomposites are prepared in a solution mixing approach. The strain-sensing performance of these as-prepared composite samples are determined through monitoring the dynamic relationship between the room temperature electrical conductivity and the mechanical properties such as elongation / compression stress. Specifically, a real time correlation has been demonstrated through simultaneously recording the changes of electrical conductivity and stress upon repeated elongation / compression cycles. The morphology of different carbon nanofillers in the polymer matrix is studied by scanning electron microscopy, and thermal properties have been investigated through thermal gravimetric analysis. The difference in filler dimension of the carbon nanofillers are observed to be responsible for the changes in electrical conductivity. The strain sensitivity and cycling stability performance are discussed on detail and the mechanism is also proposed. 

Multi-functional polymer nancomposites reinforced with carbon nano-fillers including graphene, graphene nanoplatelets, carbon nanotubes and carbon nanofibers are prepared for strain sensing applications. Polyurethane is selected as matrix for large strain applications due to its excellent elastic properties, while natural rubber matrix pretreated with carbon black is used for heavy duty small stain application attributed to its strong mechanical properties. The polyurethane nanocomposites are synthesized via a surface-initiatedpolymerization (SIP) method and the natural rubber nanocomposites are prepared in a solution mixing approach. The strain-sensing performance of these as-prepared composite samples are determined through monitoring the dynamic relationship between the room temperature electrical conductivity and the mechanical properties such as elongation / compression stress. Specifically, a real time correlation has been demonstrated through simultaneously recording the changes of electrical conductivity and stress upon repeated elongation / compression cycles. The morphology of different carbon nanofillers in the polymer matrix is studied by scanning electron microscopy, and thermal properties have been investigated through thermal gravimetric analysis. The difference in filler dimension of the carbon nanofillers are observed to be responsible for the changes in electrical conductivity. The strain sensitivity and cycling stability performance are discussed on detail and the mechanism is also proposed.