Plastics — Determination of fracture toughness (GIC and KIC) — Linear elastic fracture mechanics (LEFM) approach (ISO 13586:2018)
This document specifies the principles for determining the fracture toughness of plastics in the crack-opening mode (mode I) under defined conditions. Two test methods with cracked specimens aredefined, namely three-point-bending tests and compact-specimen tensile tests in order to suit differenttypes of equipment available or different types of material.The methods are suitable for use with the following range of materials, including their compoundscontaining short fibres of the length ≤ 7,5 mm:— rigid and semi-rigid thermoplastic moulding, extrusion and casting materials — rigid and semi-rigid thermosetting moulding and casting materials.In general, short fibre lengths of 0,1 mm to 7,5 mm are known to cause heterogeneity and anisotropyin the crack tip fracture process zone. Therefore, where relevant, Annex B offers some guidelines toextend the application of the same testing procedure, with some reservations, to rigid and semi-rigidthermoplastic or thermosetting plastics containing such short fibres.Certain restrictions on the linearity of the load-displacement diagram, on the specimen width and onthe thickness are imposed to ensure validity (see 6.4) since the scheme used assumes linear elasticbehaviour of the cracked material and a state of plane strain at the crack tip. Finally, the crack needsto be sharp enough so that an even sharper crack does not result in significantly lower values of themeasured properties.
View in