Evaluation of stress induced damage in composite material

Priston, A.-M., 1997. Evaluation of stress induced damage in composite material. PhD, Nottingham Trent University.

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The aim of this work was to investigate the growth of damage within a composite material. The work involved the use of acoustic emission to monitor the growth and evolution of damage within a composite material, A second part of the work considered the reduction in composite material elastic modulus to reflect the evolution of this damage in these composite materials.

The many failure mechanisms in the composite material produced different acoustic emission waveforms. The waveform parameters amplitude, ringdown count and risetime, were used to cluster the acoustic emission events into groups that characterised the evolution of damage in unidirectional glass fibre polyester composite material. The occurrence of high energy Cluster 1 events was confined to experimental periods where fibre debonding or failures were expected. Throughout the experiment small amplitude acoustic emission events were related to the deformation of the matrix.

A mesoscopic continuum damage model was developed to model the development of matrix cracking and fibre debonding damage in a composite material. The two increasing damage parameters (d, d') reflected the accumulation of damage by the reduction in the transverse and shear moduli. The fibre debonding from the matrix was controlled by the transverse stresses relative to the fibre pulling the fibre away from the matrix. The matrix crack was modelled as a combination of shear and transverse stresses.

Finite element analysis was combined with the model to provide examples of the damage growth pattern for a range of composite material with changing fibre angles. The results from three angle orientations showed that damage was initiated at a lower stress for weaker material with larger fibre angles. The growth patterns for the different angles were not similar, reflecting the differing development of shear and transverse induced damage. The influence of the element dimension in the mesh was tested with two different sizes and found to produce similar results.

Item Type: Thesis
Creators: Priston, A.-M.
Date: 1997
ISBN: 9781369325072
Divisions: Professional Services > Libraries and Learning Resources
Record created by: Laura Ward
Date Added: 25 Jun 2021 09:28
Last Modified: 01 Nov 2023 15:00
URI: https://irep.ntu.ac.uk/id/eprint/43232

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