Modelling and Design of Multi-Material Composite Joints with Tailored Interlayer

  • Siddharth Tampi

Student thesis: Master's Thesis

Abstract

In this study, a group of two-dimensional (Plane-stress and Plane-strain) theoretical models are presented for the stress analysis of adhesively bonded single-lap composite joints subjected to thermo-mechanical loads. These models are developed using a variational method which minimizes the complementary energy in this multi-material system. The adherends are regarded as orthotropic continuum while the adhesive is treated as isotropic continuum. Effect of thickness variation on shear and peel stresses of the inter layer are considered in this formulation. All the traction free boundary conditions are exactly satisfied. Peel and shear stresses obtained from plane-strain analytical models considering homogenous interlayer i.e., mono-modulus bondline are in good agreement with the ?nite element predictions. Subsequently, analytical models accounting for the inhomogenous properties of adhesive interlayer are developed and validated by the corresponding computational models. Finite element models with variable modulus adhesive interlayer are developed using Abaqus FEA through a user written subroutine called UMAT. Motivated by significant improvements in peel and shear performance of the joints with inhomogenous interlayer, prototypes of these joints with tailored interlayers are additively manufactured using a multi-material 3D Printer Objet260 Connex. Experimental results of these interface graded 3D printed joints are in line with the predictions of the theoretical models and open up a new avenue for prototyping multi material structural system using 3D Printing.
Date of AwardJul 2014
Original languageAmerican English
SupervisorKumar Shanmugam (Supervisor)

Keywords

  • Multi-Material System
  • Composites
  • Variational Method
  • Shear and Peel Stresses.

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