Milad khalilian

Grade:  Master

Thesis Title:

Investigation of stiffness of an internal bone fixation made of short fiber composite by continuum damage mechanics

Year: Sept. 2019 - Sept. 2022.

Abstract:

When a broken bone cannot be treated with conventional methods such as plastering and external fixtures, the fixture should be used internally. Nowadays Short fiber composites with biocompatibility such as polyether ether ketone, are a viable alternative to traditional bone fixtures to address metal plate problems. One of the challenges in using short fiber composite plates is finding their stiffness. In this dissertation, using continuous damage mechanics, a method to evaluate the stiffness of short fiber composite is presented. In this method, the composite stiffness is extracted using a two-stage homogenization model and continuous Lemaitre damage model. The obtained model is a two-stage model for homogenization and damage investigation. In this basic model, the fibers are hypothetically divided by the same size and orientation. It is divided into each group of fibers called grain. In the first stage, after applying Lemaitre damage, Mean- Field Homogenization is used for homogenization. In Mean-field homogenization, by taking the average modulus of stiffness of the two phases of the composite using Muri-Tanka equations, homogenization between fibers and grains is performed. Finally, in the second stage, it is homogenized in the whole granulation using the Voigt equations of homogenized. In this way, the complex geometry of the bone fixture can be easily modeled. A distal radius plate was used to examine the selected injury model. The parameter of damage and homogenization models were calibrated using experimental test results. Abaqus finite element software is used to model and investigate the bone fixture. UMAT sub-routine was used for damage and input file (INP) code was used for homogenization. In conclusion, after modeling the distal radius plate, The efficiency of the model was investigated and it was concluded that the proposed model is an efficient model for the study of short fiber composite plates with different geometries.

Keywords:  Mean-field Homogenization, Internal Bone fixation, Damage Mechanics, Short Fiber Composite.