Stephen R. Hallett
University of Bristol
Composite numberUltimate tensile strengthEngineeringFinite element methodComposite laminatesConsolidation (soil)Composite materialEpoxyBridging (networking)Materials scienceCompactionTension (physics)Fracture (geology)Fracture mechanicsStructural engineeringDelaminationMechanical engineeringStress (mechanics)Fracture toughness
353Publications
53H-index
5,939Citations
Publications 368
Newest
#1Bing Zhang (UoB: University of Bristol)H-Index: 10
#2Stephen R. Hallett (UoB: University of Bristol)H-Index: 53
Last. Giuliano Allegri (UoB: University of Bristol)H-Index: 21
view all 3 authors...
Abstract null null This paper investigates a novel technique for sensing delamination in through-thickness reinforced composites based on electromagnetic induction. This sensing technique features ferromagnetic Z-pins and a pair of coils attached to a laminate; the first coil creates a magnetic field that is intensified by the ferromagnetic pins, whilst the second coil detects the magnetic flux change that is caused by the pin motion relative to the coil pair when delamination happens. This appr...
Source
#1A. Koptelov (UoB: University of Bristol)H-Index: 1
#2Jonathan P Belnoue (UoB: University of Bristol)H-Index: 18
Last. Dmitry Ivanov (UoB: University of Bristol)H-Index: 22
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Abstract null null Any composite manufacturing method requires an application of a carefully designed consolidation process to ensure the suppression of voids in the laminate, establish bonding in laminate layers and prevent dimensional or fibre-path defects. The optimisation of consolidation processes relies on the characterisation of the composite precursors’ deformability. There are multiple mechanisms occurring in consolidation and various experimental programmes have been suggested in the l...
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#1X.C. Sun (UoB: University of Bristol)H-Index: 6
#2Jonathan P Belnoue (UoB: University of Bristol)H-Index: 18
Last. Stephen R. HallettH-Index: 53
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Abstract null null Automated Fibre Placement (AFP) allows for efficient deposition of composite prepreg materials at large scale in a reliable and reproducible way, while keeping human effort to a minimum. However, the technique is not perfectly suited to manufacturing small/medium parts with complex geometries. Deviation between as-designed and as-manufactured parts is almost inevitable, as is the occurrence of process-induced defects. In this study, an alternative design and manufacturing proc...
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#1Tharan M G GordonH-Index: 1
#2Xiaodong Xu (University of the West of England)H-Index: 94
Last. Byung-Chul Kim (UoB: University of Bristol)H-Index: 24
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Abstract null null Composite laminate thickness tapering is essential for weight efficient structures. This is achieved by terminating specific plies, but these can in turn act as sites for delamination initiation. One area of importance is the spacing between adjacent ply drops, which can have a significant impact on the delamination stress. In this work, a novel tape scarfing method that applies a tapered profile to dropped ply ends was used on unidirectional tapered laminate specimens with mu...
Source
#1Bing Zhang (UoB: University of Bristol)H-Index: 10
#2Giuliano Allegri (UoB: University of Bristol)H-Index: 21
Last. Stephen R. Hallett (UoB: University of Bristol)H-Index: 53
view all 3 authors...
Abstract null null This paper presents for the first time a novel numerical technique for modelling fatigue delamination growth in fibre reinforced composites, which is based on coupling two twin cohesive zone models with a single-hidden-layer artificial neural network. The simulation approach proposed here can describe composites fatigue delamination under negative & positive stress ratios and the full range of mode mixities. In the modelling strategy, each segment of a composites interface is ...
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#1Mario A. Valverde (TUD: Dresden University of Technology)H-Index: 2
#2Jonathan P Belnoue (UoB: University of Bristol)H-Index: 18
Last. Stephen R. Hallett (UoB: University of Bristol)H-Index: 53
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Abstract null null This investigation presents a methodology for the characterisation of thermoplastic composite materials under rapid processing conditions, as is needed for understanding the flow mechanisms in Unidirectional (UD) tapes. A bespoke compaction rig was designed and constructed to carry out a series of high temperature ramp-dwell loading experiments on CF/PPS (Carbon Fibre/Polyphenylene Sulphide) and CF/PEEK (Carbon Fibre/Polyetheretherketone) specimens. Significant deformations we...
Source
#1Bing Zhang (UoB: University of Bristol)H-Index: 10
#2Luiz F. Kawashita (UoB: University of Bristol)H-Index: 14
Last. Stephen R. HallettH-Index: 53
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Last. James KratzH-Index: 10
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The study of defects and their influence on the performance of composite structures is well documented. However, simplifications are often made regarding the morphology of these defects. As part of the CerTest project, a database of composite features and defects is being built, for which an assessment must be made of what information is relevant. This study looks specifically at out-of-plane waviness and seeks to investigate whether the commonly used severity metrics (e.g. maximum angle) are su...
Source
#2Jonathan P BelnoueH-Index: 18
Last. Stephen R. HallettH-Index: 53
view all 5 authors...
One of the most widely used automated manufacturing processes for composite parts is automated fibre placement (AFP). The deposition process involves the simultaneous warming, lay-up and consolidation of prepreg consisting of multitude of process parameters. Currently, AFP process parameters that ensure part conformance are derived by expensive and time-consuming trial-and-error approaches. The aim of this study is to demonstrate how physics-based finite element simulations that can predict the ...
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Abstract null null Automated Fibre Placement (AFP) is a manufacturing technique to produce large, high quality composite parts, where preimpregnated carbon fibre tapes are laid side-by-side to generate the composite preform. Thickness changes within a component are realised through internal ply terminations, with the tapes being cut perpendicular to the fibre direction. In plies laid up at an angle to the taper direction, the AFP tape cuts create saw-tooth shaped ply drop tips. This increases th...
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