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Title: Damping effects of debonded composites
Author: Lord, Charles
ISNI:       0000 0004 2745 9305
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2012
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Numerical simulations and analytical models are increasingly being sought for the design and behaviour prediction of composite materials. The use of high-performance composite materials is a growing area particularly in civilian and defence related applications. This growth demands the understanding and ability to predict how these materials will behave under their exposed environments. In this thesis, the displacement behaviour of naturally debonded composites (NDCs) from out-of-plane bending conditions is investigated. A detailed experimental programme is conducted to ascertain the phenomenological behaviours of these systems from steady-state responses for forced harmonic loading and freevibrations. The stiffness and energy dissipation behaviour are examined and a finite element (FE) model describing their behaviour is developed. Using the FE model, the experimental programme is extended through simulations and analytical models are developed to predict the displacement response behaviour. Through the exploitation of the analytical models, a linearisation is used to extract the bulk effective material properties and a constitutive model is developed to describe multi-layered 0JDCs that are reduced to a single layer describing their steady-state responses. The friction between each of the layers is included in the analytical model and is shown to have distinct behaviour for these types of composites. Acceptable agreement is observed between the analytical model predictions, the FE model and the experiments. It is well known that prevention of failure for vibratory exposed structures is a continuing challenge and that although the characterisation of damping in vibrating structures has long been an active area of research in structural dynamics, it is usually limited to experimental data. As the exploitation of lighter and more efficient structures is becoming more prevalent, the need for alternative damping materials and systems is overwhelmingly necessary. The use of NDCs poses as a viable candidate for rectifying some of these challenges, particularly since they can be designed with high levels of accuracy as opposed to a rough estimation as with many damping systems. From this work it is shown that layered NDCs have the ability to dissipate large amounts of energy from exploiting their frictional interfaces. There are many areas that NDCs could serve to be useful as damping systems.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available