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Title: Interlaminar crack arrest in composites
Author: Yasaee, Mehdi
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2012
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The formation of damage in a fibre reinforced polymer composite is, in the absence of plastic deformation, an inevitable feature of the various mechanisms by which energy is absorbed. To develop a damage tolerant composite material it is essential to understand and characterise the expected damage morphologies and subsequently design to mitigate their manifestation. Methods to achieve this have typically been attempted via optimised laminate stacking sequences or development of increasingly stronger and tougher constituents. However, an alternative approach towards damage tolerance could be to manipulate and control the formation and location of damage patterns using techniques that are generic in their application and non-detrimental to the global properties of the composite. The overarching aim of this research project was to identify a technique and demonstrate its ability to suppress interlaminar crack growth in a composite laminate under compressive loading. Initial literature review on the subject of interlaminar crack arrest determined six different techniques as potential candidates for the purpose of suppression and manipulation of delamination propagation within a composite material. These methods where subsequently explored experimentally which helped highlight discrete interleaved materials as the most promising technique. Further investigation of interleaving materials aided in characterisation of various interleaved material types with thermoplastic films exhibiting the most desirable properties. Discretely spaced thermoplastic films were then implemented in a composite panel and successfully shown to suppress delaminations induced through low velocity impact tests. Simulations studies confirmed that influence of delaniination interface location on the compressive strength of composite dominates over the overall damage footprint area. Further experimental tests successfully demonstrated the control of delamination damage propagation in a panel under cyclic compressive loading using discrete interleaved films. Although current practice for composites design in safety critical applications is to employ a 'no growth' damage tolerance design philosophy, the hypothesis of this study was to promote a re-evaluation of this mind set. There are many potential application of the proposed technique which raises stimulating suggestions for future work.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available