Mechanical properties and damage tolerance of aerospace composite materials containing CVM sensors

Kousourakis, A 2008, Mechanical properties and damage tolerance of aerospace composite materials containing CVM sensors, Doctor of Philosophy (PhD), Aerospace, Mechanical and Manufacturing Engineering, RMIT University.


Document type: Thesis
Collection: Theses

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Title Mechanical properties and damage tolerance of aerospace composite materials containing CVM sensors
Author(s) Kousourakis, A
Year 2008
Abstract The PhD thesis evaluates the mechanical properties and damage tolerance of aerospace carbon/epoxy laminates containing long, narrow interlaminar galleries. The term 'galleries' refers to thin and long holes in a laminate used for the installation of small measuring devices, such as structural health monitoring (SHM) sensors. The galleries considered in this study are similar to those used in a novel SHM system known as 'Comparative Vacuum Monitoring (CVM)'. CVM was developed by the Australian company - Structural Monitoring Systems (SMS) - for damage detection in aircraft structures. CVM is a SHM system that utilises pressure differentials between a parallel series of galleries at atmospheric or low pressure to detect damage initiation and propagation. Thus far, CVM has been used for the monitoring of surface cracks in metallic structures using surface mounted sensors. Recent research has also demonstrated that it may be possible to monitor damage along the bond-line of both metallic and composite joints usi ng CVM. The ability of CVM sensors to detect delamination damage inside composite structures is less well understood. It is envisaged that CVM can be used for the through-life health monitoring of composite aircraft structures prone to delamination damage. However, a major concern with applying CVM to composite laminates is the open-hole design of the galleries that may initiate damage growth under external loading. Material property data, structural tests, and models for predicting the properties of laminates containing galleries is needed before CVM technology can be certified for use in aircraft composite structures.

The primary objectives of this PhD thesis are the development of an optimum process method for introducing multiple interlaminar CVM galleries in composite laminates; the development of a validated model for calculating changes to the mechanical properties of laminates containing CVM galleries; and the determination of optimum CVM gallery shape, size and orientation combinations for minimising the effect of the galleries on the mechanical properties of laminates.

The effects of the shape, size and orientation of CVM galleries on the mechanical properties of carbon/epoxy laminates are evaluated by an extensive experimental research program, and the results are presented in the thesis. The properties investigated include the in-plane tensile and compressive properties, tensile and compressive fatigue life, through-thickness tensile strength, interlaminar shear strength, mode I and mode II interlaminar fracture toughness, and impact damage resistance. The results from tensile tests on lap-joints and T-joints containing CVM galleries are also presented.
Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Aerospace, Mechanical and Manufacturing Engineering
Keyword(s) Aerospace engineering - Materials
Composite materials
Delamination
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