Material Properties Stereolithography somos 7110 resin: mechanical behavior and fractography of parts post-cured by different methods G.V. Salmoria a,b, * , C.H. Ahrens a , M. Fredel b , V. Soldi c , A.T.N. Pires c a CIMJECT, Laborato ´rio de Projeto e Fabricac ¸a ˜o de Componentes de Pla ´stico, Universidade Federal de Santa Catarina, UFSC, 88040-900 Floriano ´polis, SC, Brazil b LABMAT, Laborato ´rio de Materiais, Departamento de Engenharia Meca ˆnica, Universidade Federal de Santa Catarina, UFSC, 88040-900 Floriano ´polis, SC, Brazil c POLIMAT, Grupo de Estudo em Materiais Polime ´ricos, Departamento de Quı ´mica, Universidade Federal de Santa Catarina, UFSC, 88040-900 Floriano ´polis, SC, Brazil Received 12 August 2004; accepted 14 September 2004 Abstract Different types of photopolymers, also called photosensitive resins, have been used in the stereolithography process to obtain parts with specific shapes and applications. Somos 7110 resin was used to build samples to study their thermal and mechanical behavior. Fractography analysis following tensile or impact tests, after exposure of samples to ultraviolet radiation or thermal treatment, was correlated with mechanical properties. Brittle fracture behavior was observed in all samples studied and plastic deformation was present in some regions of green samples, showing layer ordering in the microstructure originating from the stereolithography process. The samples post-cured by conventional heating demonstrated improved mechanical properties and low defect susceptibility. q 2004 Elsevier Ltd. All rights reserved. Keywords: Stereolithography; Mechanical tests; Fractography 1. Introduction The stereolithography (SL) process permits the rapid manufacture of parts and objects by laser curing, layer-by- layer, of a photo-sensitive resin. The main applications of the SL process are the production of visual prototypes and models used in the automobile, electric, biomedical and aerospace areas. Stereolithography is also applied in the manufacture of functional prototypes such as rapid tools [1,2]. The thermal and mechanical properties are of great importance for rapid tools such as molds for injection of thermoplastics, since these tools are subjected to particular conditions of work with temperature variations and mechanical requirements [3–5]. The mechanical properties of parts manufactured for stereolithography depend on the degree of cure of the photo- sensitive resin. Manufacture parameters, such as the laser power distribution and scanning speed during construction, resin characteristics such as monomers, oligomers and curing agent compositions, maximum density of cross-linking, photosensitivity, rate and degree of cure, and post-cure method are very important to define the structure and properties of SL samples [1,2]. Knowledge of the relation- ship between resin structure and properties is useful in the SL tools manufacturing process, application and quality control. This work correlates the surface fracture features of samples tested by tensile or impact methods with their mechanical properties resulting from different post-cure treatments. 0142-9418/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.polymertesting.2004.09.008 Polymer Testing 24 (2005) 157–162 www.elsevier.com/locate/polytest * Corresponding author. LABMAT, Laborato ´rio de Materiais, Departamento de Engenharia Meca ˆnica, Universidade Federal de Santa Catarina, UFSC, 88040-900 Floriano ´polis, Brazil. E-mail address: gsalmoria@cimject.ufsc.br (G.V. Salmoria).