Local Reinforcemente Effect of Embedded Strain Gauges

The reinforcement effect of strain gauges installed on low Young's modulus materials has receivedattention by many researchers with respect to both strain gauges installed on the surface [1,2] andembedded inside the material [3,4].In the case of strain gauges installed on the surface, the evaluation of the local reinforcementeffect gives [5] the following correction coefficient C, i.e. the ratio between the actual strain (without the strain gauge) and the strain ' measured by the strain gauge:*' 1 sgsECE (1)being* sg g , sgsg sgsg sg sgt L LE EL t t (2)where Esg is the Young’s modulus of the strain gauge, *Esg is a characteristic of the strain gaugewhich gives the strain gauge sensitivity to the reinforcement effect (reduced Young’s modulus of thestrain gauge), Es is the Young’s modulus of the specimen, tsg , Lg , Lsg are respectively thickness, totalgauge length and grid length of the strain gauge, and is the mean value of a function determined by a theoretical analysis [5]. This paper concerns the local reinforcement effect ofembedded strain gauges that are frequently used especially inside plastic and composite materials.