Use this URL to cite or link to this record in EThOS:
Title: Tufting of complex composite structures
Author: Lombetti, D. M.
ISNI:       0000 0004 5989 6390
Awarding Body: Cranfield University
Current Institution: Cranfield University
Date of Award: 2015
Availability of Full Text:
Access from EThOS:
Access from Institution:
This study focuses on the effect of tufting on the mechanical and electrical properties of carbon composites using a variety of tuft materials, such as aramid, steel and copper. Several configurations were investigated based on a case study, involving the reinforcement of stiffener-to-skin interfaces of a tail cone. The effect of tuft and base composite material, tufting depth and inclination on the delamination resistance in mode I was evaluated, the associated bridging laws were determined and the failure mechanisms were identified. A simplified superposition model of the delamination response of tufted composites was developed. The electrical performance of tufted composites was determined in simulated lightning strike tests and set against the through-the-thickness electrical conductivity of the materials. The results of mechanical testing showed that the delamination performance depends strongly on the material response of the tufts, with both the bridging behaviour and final toughness levels influenced directly by the strength, ductility and ultimate strain of the tufts. Interactions between the tufts and the surrounding composite, such as interfacial shear and bridging induced by tuft pull-out, play a significant role in the overall behaviour generating a deviation from a simple superposition of the base material and tuft response. The balance between interfacial shear and tuft elongation results in a decreasing trend of delamination toughness with increasing tufting depth for low ductility materials, whilst the trend is reversed for the high ductility copper tufts. This balance is also affected by the properties of the base material, with tougher matrices leading to dominance of shear effects and a weaker enhancement introduced by tufting. Inclination of tufts leads to an increase in crack energy release rate due to the activation of a ploughing mechanism. Metallic and carbon tufts have a positive effect on lightning strike response, with copper tufting offering strike protection at an improved level compared to standard copper mesh solutions.
Supervisor: Skordos, Alexandros A. ; Partridge, Ivana K. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Metallic tufts ; Through-the-thickness reinforcement ; Delamination ; Bridging law ; Lightning strike protection ; Electrical conductivity ; Carbon fibres