Quantitative analysis of bending hysteresis by real-time monitoring of curvature in flexible polymeric films

Abstract

The measurement of bending curvature of polymer films characterised the bending hysteresis as a precursor phenomenon of fracture and fatigue. The measurement also enables us to predict the occurrence of bending hysteresis.

Novel Bending Sensor Based on a Solution-Processed Cu2O Film with High Resolution Covering a Wide Curvature Range

“…The bending would lead to the expansion of the distance between the grains along the bending direction, resulting in the increase of grain-boundary resistance . Because the distance between the grains expands in proportion to the applied strain (ε), the resistance variation in the bending changes linearly with the curvature (κ) calculated from the formula κ = (2/ d ) × ε . The combined effect of this grain-boundary resistance and the piezoresistive effect led to the high linear response of the Cu 2 O bending sensor shown in region II.…”

Bending Fatigue Analysis of Various Polymer Films by Real-Time Monitoring of the Radius of Curvature and Heat Generation

“…A radius of curvature ( r ) of polymer films under cyclic bending was obtained from the cross-sectional images captured with the CCD camera to analyze the fatigue behavior. The shape profiles of the films were fitted with a sixth-degree polynomial function ( y = prefix∑ k = 0 6 a k x k ), and then the value of r was geometrically calculated from the obtained function using the following equation: , r = true{ 1 + true( d y d x true) 2 true} 3 / 2 − d 2 y d x 2 In addition, the fractured polymer films were analyzed by POM, scanning electron microscopy (SEM; JSM-6610LA, JEOL Ltd., Japan), and ATR-IR measurements. Heat generation of cyclic bending polymer films was monitored with a thermography camera (PI-640, ALGO Co., Japan).…”

“…), and then the value of r was geometrically calculated from the obtained function using the following equation: 29,30 ( )…”

Bending creep behaviour of various polymer films analysed by surface strain measurement

“…Experimental studies targeting bending creep in polymer films are notably scarce. This limitation can be attributed to the challenges associated with accurately and precisely measuring strain in bent polymer films using conventional methods such as curvature analysis, [17][18][19] strain gauges, [20][21][22][23] and the digital image correlation (DIC) method. [24][25][26][27] Although these methods have the capability to measure surface strain in bending polymer films, their effectiveness is limited by various experimental constraints, e.g., curvature analysis suffers from the interference of light caused by bending, which affects accurate measurements and reduces the reliability of results.…”