Assessing the In-plane Shear Failure of GFRP Laminates and Sandwich Structures

Date of Award


Degree Name

Ph.D. in Mechanical Engineering


Department of Mechanical and Aerospace Engineering and Renewable and Clean Energy


Advisor: Elias Toubia


Shear walls, diaphragms, and shear webs structures are generally subjected to in-plane shear loading. Only a small number of test data regarding the in-plane shear behavior of Glass Fiber Reinforced Polymer (FRP) sandwich structures is currently available. Using the picture frame shear test method [ASTM D8067], this work reports a novel systematic experimental approach coupled with both 2D and 3D Digital Image Correlation (DIC) techniques to characterize the failure modes of sandwich structures. Constituent materials such as plain foams, laminates, and sandwich panels featuring different foam core densities and face-sheet thicknesses were tested. The principal strain-ratio measurement technique presented in this work was able to outline the interaction in failure modes. A simplified analytical model to assess the core in-plane shear load contribution in sandwich structure was developed and validated. The core contribution to the structure was clear and should be taken into account for high-density foam materials and web-reinforced core designs. An experimental investigation was also included to study the effect of local discontinuities arising from the center hole and low-velocity impact damage on the in-plane shear behavior of thin laminates representing the face-sheets of the sandwich panels. Using Ultrasonic Testing, damaged zones were assessed and represented as elliptical and circular holes to theoretically predict the in-plane shear buckling load of thin composite plates. This study produced a new in-plane shear data along with simplified design equations that will assist engineers to confidently size, design, and predict the in-plane shear capacity of GFRP laminates and sandwich structural members.


Mechanical Engineering, Sandwich Composites, In-plane Shear, Picture Frame Shear Test Method, Shear Failure Modes, Analytical Solutions

Rights Statement

Copyright © 2018, author