Fracture Toughness and Damage Tolerance in Vat-Photopolymerised Thermosets: Crack Preparation, Cure State, Anisotropy and Qualification
Segurola, Juan
2026-08-27 · Informe · Versión 1.2
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Vat-photopolymerised thermosets are frequently described as tough, impact resistant or thermoplastic-like using tensile elongation, work-to-break, flexural response or pendulum-impact data. These quantities are useful, but none is interchangeable with resistance to the initiation and propagation of a sharp crack. This review develops a qualification framework for fracture toughness and damage tolerance in SLA, DLP and LCD/MSLA printed thermosets. It distinguishes unnotched tensile toughness, work of fracture, impact strength, notch sensitivity, conditional stress-intensity values, valid plane-strain KIC and GIC, and elastic- plastic J-R behaviour. Primary studies demonstrate that apparent fracture response can change with printing orientation, exposure, layer thickness, post-cure, specimen size, notch geometry, resin colour, environment and crack-plane alignment. They also show that different experimental geometries can produce different orientation rankings because crack deflection and layer-interface interactions alter the fracture path. Printed notches are valuable for rapid screening, but they are not automatically equivalent to a sufficiently sharp precrack under ISO 13586 or ASTM D5045. Toughening routes based on urethane-acrylate blending, graphene, phase-separated aromatic polyester modifiers and reversible intermolecular interactions can improve resistance to failure, yet each route requires crack-valid testing before a fracture-toughness claim is made. The review proposes a minimum reporting set covering material identity, printer and exposure state, specimen geometry, crack preparation, build orientation, conditioning, loading rate, validity checks, statistics and fractography. The central conclusion is that fracture toughness is a method- and state-qualified property of a cracked printed material, while damage tolerance is a broader structural demonstration linking validated fracture data to the actual flaw population, geometry, environment and service loading.