Nonlinear 3PB and 4PB Flexural Behavior and Softening Localization for Epoxy Resin E 863 Using Digital Image Correlation Technique

The effect of local strain and stress distribution in the polymeric material under out of plane loading is of interest in many applications. Flexural testing of the polymer resins is necessary to evaluate their mechanical behavior. In this paper, the flexural response of polymer resin Epon 863 mixed with the curing agent EPI-CURE 3290 using a 100/27 weight ratio has been investigated in three-point bending (3PB) and four-point bending (4PB) at different strain rates. Beams with different lengths and span to depth ratios were tested. Results show a higher flexural strength for 4PB than 3PB. Strain fields within the polymer beam structure were determined using the digital image correlation (DIC) technique to study the evolution of softening localization in 3PB and 4PB setups. Results show that the length of the softening localization is less than half of the thickness throughout the loading. The DIC technique was used to obtain the location of the neutral axis in the nonlinear stage of the material behavior. Results indicate the nonlinear variations of the neutral axis location for epoxy resin Epon E 863. The results show that the DIC technique can accurately characterize the material response of an epoxy resin for flexural loading.