Caracterización mediante métodos inversos numéricos y correlación digital de imágenes de las propiedades elásticas en el plano de materiales compuestos laminados producidos con fabricación aditiva
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In recent years, additive manufacturing technologies (3D printing) have been introduced in
different fields, such as locomotion and bioengineering, among others. Extrusion by Fused
Deposition Modeling (FDM) or Fused Filament Fabrication (FFF) is striking among the different
3D printing techniques for its versatility and capabilities. The mechanical properties of the
materials manufactured with this type of manufacturing technology depend on factors associated
to machine parameters, material density, manufacturing orientation, working parameters and
environmental conditions. Due to the process of manufacturing, materials printed through
these techniques can be considered as laminated materials. Therefore, identifying the elastic
and mechanical properties of these materials is essential for its correct use and application.
This characterization of properties is usually carried out under standards that involve varied
experimental tests in a repetitive way for each one of the constants to be identified.
New forms of identification have appeared to reduce the number of tests in the elastic characterization
of laminated composites. In these, numerical techniques of inverse solution and
of measurement of heterogeneous fields of deformation are considered, as well as the natural
characteristics of the material. The inverse procedure only requires one experiment (on the plane)
to characterize composites of carbon fibers or glass (among others). For this, methodologies
based on optimization techniques and direct solutions on reverse mathematics are used. Different
experimental tests are also used as measurement techniques. Previous research has identified a set
of difficulties to be solved, corresponding to deviations in the inferred parameters, implementation
in composites manufactured with additive manufacturing, effects of the surface finish on the
inference, efficiency of the method according to the degree of orthotropy of the material, types
of optical configurations based on standardized geometries, limitations associated with the type
of reverse solution implemented, among others.
The aim of this doctoral thesis is to improve the process of elastic identification with inverse
methods using a single experimental test of laminated composites to reduce the existing gaps in
the implementation of this methodology. For this, an algorithm based on gradient optimization
methods is designed and developed in order to minimize the adjustment of the deformation
fields of a numerical finite element model with respect to a reference obtained by non-contact
measurement in an experimental test. The evaluation of the algorithm developed for elastic
characterization is performed with 22 open-hole geometry specimens; additive manufacturing
of continuous carbon fiber and thermoplastic matrix, in symmetrical and balanced stacks with
different orthotropic grades, is used in the manufacturing of the coupons. The experimental
process is carried out in a quasi-static tensile test, where the deformation fields are captured
with digital image correlation (DIC) equipment in an appropriate configuration and with proper
preparation of the specimen surfaces
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