On the Transition in the Brittle-Ductile Failure Mode in Polymeric Materials

Response of structural use polymers subjected to impulsive loads

Spain Created on 2017.06.20 683 views
The use of polymeric materials in the design of mechanical components subjected to impact and dynamic loads, has increased in the last decades due to their impact resistance behavior, compared to other materials with greater weight and cost. A damage model capable of predicting and reproducing the failure mode transition that may occurs in some of these materials is presented. The proposed damage model is independent of the constitutive model, and considers the competition between two modes of failure acting simultaneously, one brittle and the other ductile. The criterion of brittle fracture has been formulated locally and is based on the maximum main stress on the material, establishing the fracture when that maximum principal stress reaches a critical value, which is dependent on the strain rate. On the other hand, the ductile failure criterion establishes the degradation of the material as a function of its strain energy density, allowing a progressive ductile damage to be considered in the material. This damage model has been implemented by means of a user subroutine in the finite element code Abaqus/Explicit v6.13 taking advantage of the versility and potential that this Simulia software provides. The verification of the proposed damage model was carried out using Polycarbonate as reference polymer, since it naturally exhibits failure mode transition under normal conditions of pressure and temperature. To this end, an extensive experimental campaign has been carried out, which includes characterization tests and validation tests that allow the comparison of numerical predictions with their corresponding experimental results, obtaining a good correlation between both. As a result of this comparison, a detailed analysis of the transition process in the failure mode has been performed, highlighting the need to simultaneously implement both failure criteria.
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JA Josue Aranda Ruiz
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