Comparison of analysis between the classical ESIS method and the ASTM D-7905 standard, for obtaining shear fracture toughness

Abstract

The present work is part of the characterization of glass fiber composites elaborated with a novel vinylester-urethane resin, with addition of poly for use in reinforcing materials for concrete, as a passive reinforcement or as a reinforcement for structures in use, as these resins have a higher Resistance to chemical agents, basics and vapors along with a lower exotherm facilitating the manufacture of thick laminates.Within Mode II fracture mechanics, until this 2014 there was no standard that would collect a procedure to quantify GIIC. Davies through the European Structural Integrity Society (ESIS) issued a mode II test protocol in 1992 known as ENF (End Notch Flexure) [1]ASTM D7905-14 encompasses a fairly complex procedure in which the basis for the characterization of shear fracture toughness in mode II using the final notch flexure (ENF) test is laid.This paper aims to verify the main differences between this classical procedure and the method of this standard to verify their similarities.For this purpose, a mechanical pre-characterization of the reinforced resin is carried out with high-grade fabric (780 g/cm2) with glass fiber E as well as a thinner carbon fiber composite. This characterization is performed by ENF bending tests, and the procedure of the new ASTM D-7905 standard.   [1] ASTM D5528-01, “Standard Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites”, American Society for Testing and Materials, 2001.