What is selective reinforcement in the context of AFP?
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A key benefit of using AFP to construct pressure vessels that addresses specific structural shortfalls.
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What is selective reinforcement in the context of AFP?
A key benefit of using AFP to construct pressure vessels that addresses specific structural shortfalls.
What is a limitation of the thickness profile in dome design?
It is coupled to the thickness in the cylinder region and vessel geometry.
What causes matrix microcracking in composite laminates?
Mechanical and thermal loading.
What was the theoretical reduction in composite material required when using doily reinforcement in a Type IV vessel?
Nearly 10%.
What is the primary focus of the review article?
A review of Type V composite pressure vessels and automated fibre placement based manufacturing.
How do fibres behave when placed under tension?
They self-align to geodesic paths.
What is the consequence of the build-up of microcracks in composite tanks?
It can create channels that allow gas to escape, leading to potential failure.
How much did the burst pressure increase in a Type III pressure vessel with doily layers?
By 29%.
What is the advantage of Type V pressure vessels over Type IV?
Type V eliminates the internal polymer gas barrier and relies on carbon fibre laminate for structural properties and gas leakage prevention.
How does mechanical strain affect gas permeability in composite laminates?
Gas leak rate increases with mechanical strain.
What is a significant challenge of applying AFP compared to filament winding?
AFP is less mature and used on fewer commercial products.
What is required to achieve non-geodesic paths in fibre placement?
Friction is required to prevent the fibres from slipping.
What is the main challenge in using hydrogen as an energy carrier?
Storing hydrogen with high volumetric and gravimetric density, particularly in weight-critical environments.
What impact does the layup sequence have on permeability?
Laminates with plies of the same angle grouped together show increased leakage.
What are the two advanced robotic composites manufacturing techniques?
Automated fibre placement (AFP) and automated tape laying (ATL).
What defect is commonly encountered in AFP parts that leads to non-uniform thickness?
Gaps and overlaps between tows.
What pressure range is required for storing hydrogen gas in composite pressure vessels?
350 – 700 bar.
How do stitched materials compare to unstitched materials in terms of permeability?
Stitched materials exhibit higher permeability than unstitched materials.
What effect does increased porosity have on AFP-made laminates?
It decreases the interlaminar shear strength.
What is a disadvantage of ATL compared to AFP?
ATL performs poorly on complex contours or internal geometries due to wrinkles.
What manufacturing technique is proposed to replace traditional filament winding for composite pressure vessels?
Automated fibre placement (AFP).
What is the primary function of the compaction roller in the AFP process?
To compact the incoming tow and promote adhesion to existing layers.
What is the significance of microcracking fracture toughness (MFT) in composites?
It determines when a new microcrack is formed based on energy release.
What physical limitation poses a challenge for AFP in pressure vessel manufacturing?
The large size of current AFP heads can lead to collisions with the part or tooling.
What is the typical width of tapes used in ATL?
75 – 300 mm.
What is the significance of the cut-and-add capability in AFP for pressure vessels?
It allows for selective reinforcement of dome areas without adding excess material to the cylinder.
What are the benefits of using carbon fibre in pressure vessels?
Carbon fibre allows for the construction of lightweight tanks with gravimetric storage densities more than four times that of steel vessels.
What innovative setup did Schakel et al. use to overcome challenges in small-scale tank manufacturing?
The Fraunhofer 'Multi-Material-Head' with a laser-assisted tape placement (LATP) setup.
What modeling methods are used for gas permeability in laminated composites?
Experimental/empirical methods and numerical methods.
What is a key advantage of the AFP process?
It allows for tow steering to place fibres on non-geodesic trajectories.
What weight savings were achieved in the hybrid AFP/FW tank design compared to traditional methods?
A 32% weight saving over the entirely filament wound baseline tank.
Which hydrogen fuel cell electric vehicles utilize Type IV vessels?
Toyota Mirai and Honda Clarity.
What does tow steering enable in the AFP process?
It enables full coverage of a surface and optimized variable stiffness.
What did Bois et al. develop for predicting gas flow in damaged composites?
A multiscale model applicable to composite pressure vessels.
What is the main characteristic of Type V composite pressure vessels?
Type V vessels are linerless, meaning the composite acts as both the gas barrier and load-bearing structure.
What were the weight and cost reductions achieved in the NASA and Boeing cryotank project?
Weight reduction of 25% and cost reduction of 30% compared to traditional aluminium-lithium tanks.
What is a key feature of Type IV vessels?
They have a plastic liner to prevent gas leakage.
What is the typical tow width used in AFP?
3.175 – 12.7 mm.
What factors significantly affect permeability in composite materials?
Crack density and opening displacement.
What are the advantages of Type V vessels compared to traditional vessels?
They eliminate the need for strain compatibility between the liner and composite, leading to increased fatigue performance and potential weight reduction of 10-20%.
What is variable angle tow (VAT) in the context of AFP?
A capability that allows for non-geodesic and steered paths to optimize fibre layup.
What issue does AFP equipment face due to highly curved fibre paths?
Tow buckling.
What is the significance of achieving decarbonisation targets related to hydrogen?
Hydrogen is identified as suitable for meeting climate objectives to prevent global warming greater than 1.5 °C.
What is a key feature of the compaction roller in the LATP head?
It has a large diameter and is cantilevered, allowing tape to be placed close to the headstock without collision.
How does cryogenic cycling affect crack growth in composites?
X-ray scanning and microscopy are used to map crack growth.
What manufacturing technique is traditionally used for composite pressure vessels?
Filament winding (FW).
What is a significant limitation of AFP regarding robot joints?
Numerous areas where no coverage can be achieved due to limitations in the range of motion.
How did VAT improve the bending-induced buckling load in a manufactured cylinder?
It resulted in a 28% increase in calculated buckling load compared to a quasi-isotropic layup.
How does the LATP head differ from a regular thermoset placement head?
The LATP head supports the roller without side supports, while the thermoset head supports the roller on either side.
What is Automated Fibre Placement (AFP) and how does it improve manufacturing?
AFP is an evolution of filament winding that provides high accuracy, quality, and low wastage.
What is the maximum layup rate achievable with AFP on simple geometries?
Up to 150 kg/h.
What challenge does the bend-free design of pressure vessels face?
The need to install a polar boss disrupts the required fibre pattern.
What is the width of the tape placed by the LATP head?
12 mm wide.
What challenges must be overcome for Type V vessels to be commercially viable?
Several engineering challenges related to design and manufacturing need to be addressed.
What technology merges physical processes with computer-based simulation for smart manufacturing?
Digital twins.
What is 'Continuous tow shearing' (CTS) in AFP?
A technique that allows fibres to be steered at tight radii, improving fibre placement.
What challenge does the thermoset head face in terms of material placement?
It cannot place material tangent to the headstock without collision.
What was a significant finding from the research on Type V vessels conducted by Mallick et al.?
One design achieved a 15% increase in storage volume and a 25% reduction in mass compared to an equivalent Type I tank.
What limitations were identified in the design of bend-free composite pressure vessels?
Geometric and material-induced limitations that constrain possible super ellipsoid shapes.
What are the two main challenge areas for the mass adoption of Type V pressure vessels?
Manufacturing and permeation control.
What did Qu et al. present to evaluate AFP head accessibility?
A simulation method considering the roller's ability to access the part surface and place it normal to the surface.
What type of mandrel must be removed to achieve a linerless design in Type V tanks?
A traditional soluble mandrel.
What limitation does filament winding have regarding vessel design?
Filament winding can only wrap around convex surfaces, requiring polar bosses that complicate design and add mass.
What was the outcome of Hély et al.'s simulation of the AFP layup of a complex y-shaped tube?
It was found that the geometry would be very difficult to cover with conventional AFP equipment.
What is the significance of the burst pressure achieved by Type V vessels?
One design achieved a burst pressure of 620.5 bar, close to the automotive industry standard operating pressure of 700 bar.
What is a significant challenge in using AFP for pressure vessels?
Increased permeability of AFP/ATL made laminates compared to hand layup.
What may be necessary to address manufacturing challenges with AFP hardware?
Innovating the tooling and support structure used to hold the vessel.
What is the current state of literature on Type V pressure vessels?
The existing peer-reviewed literature on Type V vessels is highly limited.
What is the ultimate leakage target specified by the US Department of Energy for hydrogen gas?
0.05 (g/hr)/kg of stored hydrogen gas.
What two phenomena dominate the permeation of gases in FRP laminates?
Diffusion and interconnected microcracking.
What has been shown to contribute significantly to total permeation in composite materials?
Leakage due to microcracking.
