Evaluation of the effect of core damage on the stiffness of Nomex honeycomb composite panels
Date
2000
Authors
Mir, Gohar Majeed
Major Professor
Advisor
Dayal, Vinay
Committee Member
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Effect of damage on Composite honeycomb panel due to low speed impact is of significance. As a result of such impact damage; crushing or wrinkling of the core, core to face de-bonding and local de-lamination of the plies occurs. The damage, however, may be invisible to human eye but can result in significant degradation of stiffness and strength of honeycomb structures. This thesis is concerned with evaluation of effect of damage in Nomex honeycomb core on stiffness of composite panel by experimental and Finite Element Methods. The typical damage pattern of Nomex honeycomb core to low speed impact is the crushing of core walls away from the core-face sheet interface. This type of damage reduces the local supporting capability of the honeycomb cell walls and thereby results in lower local stiffness / strength.
Interactive Finite Element model has been developed having option of creating single / multiple defects of different sizes at desired locations within the core material, with core modeled as either orthotropic hexagonal cell or as an homogeneous isotropic Elastic Foundation. Model is generated using Graphite/Epoxy quasi-isotropic laminates as face sheet material with Nomex paper core. The model is analyzed by FEM (Static analysis) by applying point load (equivalent force of the impacting projectile) at the node of concern or by FEM (Dynarnic analysis) by tracking the force-time history of impacting projectile mass. The core damage is modeled as a gap in the core. Number of panels were made with different defect configurations and were tested using Static Force Tester and Tap Tester. Experimental results were compared with ANSYS models (Finite Element Methods) under identical boundary conditions and loading. The sensitivity of the results of these analyses with respect to damage size and its height in the core are studied and the results are presented. Some estimates are made on the performance and effectiveness of the Tap Tester to be used as a handy and efficient NDE tool.
Series Number
Journal Issue
Is Version Of
Versions
Series
Academic or Administrative Unit
Type
thesis