Experimental Method for Calculating Young's Modulus of Paper from Elongation Test

Young's modulus from a conventional elongation test of paper is usually underestimated, mainly because slippage occurs between the specimen and the grips during loading. A more accurate Young's modulus is sometimes required for a precise discussion of paper science or the suitable material design of paper. Although the vibrating reed method and the ultrasonic method have both been proposed for determining Young's modulus of paper, these techniques are limited by the requirement of special devices and a complicated measurement procedure. Therefore, a modified calculation method for Young's modulus from the elongation test is discussed in this study. The apparent deformation (Ģd) of paper in a conventional elongation test can be divided into two parts, a real sheet deformation (Ģf) and a false deformation which includes the slippage (Ģs). The percentage of Ģs of the apparent strain becomes larger as span 1 decreases, because for a certain kind of paper at a certain external loading level Ģs is considered to be the same regardless of test span. The amount of Ģs at a given load can be obtained by extrapolating the relationship between apparent deformation at the load level and test span to zero span. Thus, Young's modulus can be calculated after the correction of sheet strain by the value of Ģs. The effect of restraint of lateral contraction near the grips on extensional rigidity was found to be small when calculated by the finite element method, provided that the span is more than twice the sample width. The results suggest that the specimen span should be more than 30 mm. Young's modulus corrected in this way was fairly close to that obtained from the vibrating reed method.