I. Core Breakthroughs

Breakthrough 1 : Rare domestically V Thermoplastic for Type‑less, Unlined Liquid Hydrogen Tanks ATL Complete engineered process package

Currently, the mainstream methods for hydrogen storage are IV Type plastic-lined wound tank, V The all‑composite, linerless structure offers significant lightweighting advantages; however, in‑situ thermoplastic forming of doubly curved spherical surfaces currently lacks a mature manufacturing process. This paper successfully demonstrates the complete integration of… CF/PA11 From material qualification and parameter optimization to robotic offline path planning, forming, machining, and pneumatic demolding, this end-to-end process fills a critical gap in the manufacturing technology for cryogenic thermoplastic automated tape‑layup hydrogen storage vessels.

Breakthrough 2 : Quantifying high viscosity PA11 Molding parameter thresholds, providing the industry’s optimal process window.

PA11 The room-temperature viscosity is as high as 150Pa ・ s , interlayer debonding is prone to occur at low temperatures, 9  Group gradient SLS The experiment clearly indicates the temperature. -  Velocity coupling rule: At excessively low temperatures, resin melting is incomplete; at excessively high laying speeds, the melt does not have sufficient time to impregnate. 300 °C, 200 mm/s Combination achieves the highest 16.81 MPa The single‑lap shear strength balances molding efficiency with interfacial bonding strength, providing a quantitative benchmark for the process optimization of thermoplastic hydrogen storage vessels.

Breakthrough 3 : Addressing the inherent defects of hyperbolic spherical layup and establishing a variable-thickness, gradient-layup design.

For the hemispherical pole region, head impact and ± are applied. 7 ° Caused by tow offset 7 – 10mm Addressing the challenge of excessively large gaps, a scheme for interpolating robot path waypoints is proposed; a gradient layup structure—thin at the equator and thickened toward the poles—is designed to meet the pressure‑bearing requirements of hydrogen storage under explosive conditions, thereby reducing the gap. /  Overlap control is within ± 5mm Within design tolerances, no wrinkles or delamination are present.

Breakthrough 4 : End-to-end digital twin for molding processes + Innovative Non-Destructive Pneumatic Demolding Solution

In-house development Smarthub Real-time acquisition of laser temperature, clamping force, and robot coordinates, with synchronous generation of a thermal-field digital twin; to address the challenge of thermoplastic cooling‑induced shrinkage and mold clamping, an in‑mold multi‑channel system has been developed. 2 bar A high-pressure air‑assisted demolding process prevents delamination damage caused by manual prying, significantly improving the yield of qualified finished products.

II. Technological Innovation

Innovation 1  Suitable for low-temperature hydrogen storage CF/PA11 Materials characterization system

• DSC Standardized Thermal Testing: 80 ℃ pre-dehumidification elimination PA11 Water absorption–induced warping interference, material measured Tg=94.44 °C, Tm=188.45 °C, 22% Crystallinity, compatible with 120K Under liquid hydrogen cryogenic conditions, it exhibits resistance to transverse microcracks.
• Quantitative characterization of gold-phase porosity: 500  Observation under a scanning electron microscope reveals that, under the optimal process conditions, the porosity of the formed part is less than 1% , meeting the hydrogen permeation limit requirements;
• SLS Single-lap shear DOE Experiment: Fixed 500N Compaction force, classification 220/260/300 °C, 200/250/300 mm/s Three-level variables: the quantitative relationship between speed enhancement and the degradation of bonding strength.

Innovation 2  Six-axis robot + Dual external rotary axes ATL Integrated Molding Equipment

• Hardware configuration: FANUC Six-axis robot + Compatibility Laser placement head, 6 kW Infrared laser closed-loop temperature measurement and control prevent thermal degradation of the resin.
• Raw Material Temperature-Controlled Storage: Dedicated Humidity-Controlled Warehouse 60 Store the prepreg tapes at a constant temperature of ℃ to inhibit… PA11 Moisture absorption causes warping after installation.
• Offline simulation link: Rhino Modeling + ADDPath Path planning detects potential collisions between the mold’s extremity and the placement head in advance, enabling early trajectory corrections and reducing on-site trial-and-error.

Innovation 3  Defect-Control Technology for Hyperbolic Hemispherical Gradient Laminates

• Layup configuration: 40  Layer‑quasi‑anisotropic arrangement ( 90 ° / ± 7 °), equatorial wall thickness 4mm Gradually transition to the pole. 8mm , matching the distribution of compressive stress;
• Gap suppression scheme: Encrypt the robot program’s interpolation points to reduce the surface‑fiber‑bundle angle deviation error to ± 1 Within °, eliminate 7 – 10mm Excessive clearance;
• First-layer positioning process: mold‑mounted double-sided adhesive. Kapton Adhesive film addresses the issues of insufficient adhesion and delamination between thermoplastic materials and aluminum molds.

Innovation 4  Pneumatic demolding + End-to-End Digital Governance Solution

• Mold Design: Uniform Distribution of Cast-Aluminum Hemispherical Fixtures 16  one 24mm High-pressure gas pores, introduced after molding. 2 bar The compressed air is evenly distributed across the components, with no external forces causing damage.
• Smarthub Data Acquisition System: Synchronously captures laser temperature, compaction pressure, and robot coordinates in real time, generates a full‑field thermal map, constructs a digital twin of the hydrogen‑storage hemispherical structure, and enables traceability of every layer‑placement process parameter.

III. Application Scenarios

• Liquid Hydrogen Aviation / In-vehicle V Type of unlined hydrogen storage vessel (core application scenario)

Civil aircraft, heavy-duty trucks, and cryogenic liquid hydrogen storage and transport tanks for ships—alternatives to… IV The in-mold winding structure achieves significant weight reduction, thermoplastic. PA11 Low-temperature resistance and hydrogen permeation rate meet the standards, ATL Automated tape laying is well-suited for the mass production of large‑size hemispherical components.

• Segmented Shell of a Cryogenic Hydrogen Tank for Space Rockets

The spherical segmented components of the launch vehicle’s liquid hydrogen tank feature thermoplastic composites that can be repeatedly repaired by heat, eliminate the risk of hydrogen embrittlement through the absence of a metallic liner, and employ graded ply layups to precisely match regions of high and low stress.

• High-pressure hydrogen storage vessel for stationary energy-storage hydrogen refueling stations

Large-capacity cryogenic hydrogen storage tanks for hydrogen refueling stations feature hyperbolic hemispherical standardized components that can be modularly assembled, with automated forming reducing manual lay-up costs and controllable porosity ensuring compliance with safety acceptance criteria.

• Thermoplastic ATL Equipment Process Calibration Reference

For hydrogen storage composite material equipment manufacturers, the complete set DOE Tests, path planning, and demolding schemes can serve as PA A standardized test procedure for the thermoplastic tape‑laying process, enabling rapid equipment commissioning.

• Low-Temperature Composite Material Research and Testing Benchmark

Universities /  The institute conducts benchmarking tests for low-temperature composite molding, providing comprehensive thermal analysis, shear mechanical testing, and microstructural porosity measurement methods, along with datasets of process parameters.

IV. Summary of the Article

(1) Core Research Findings

• CF/PA11 Optimal thermoplastic hemispherical hydrogen storage ATL Process: Laser 300 °C, laying speed 200mm/s , Compaction pressure 500N , single-lap shear strength 16.81MPa , the porosity of the molded part is less than 1% , compatible with 6 bar Liquid hydrogen under cryogenic conditions;
• PA11 High resin viscosity significantly reduces interlayer adhesion strength as lay-up speed increases; to achieve high‑speed mass production, laser heat input must be increased in tandem.
• In the hyperbolic pole region, head‑to‑head collisions and fiber‑bundle angle deviations are prone to occur, leading to excessively large gaps. Increasing the density of interpolation points in the robot’s trajectory can keep defects within the design tolerance of ±. 5mm Within;
• Multi-channel aluminum die casting mold 2 bar High-pressure air demolding can prevent thermal‑induced shrinkage and delamination, combined with… Smarthub The system enables end-to-end digital twin–based traceability.

(II) Engineering Application Value

Traditional IV The inner liner of type hydrogen storage tanks is prone to aging and exhibits a noticeable weight gain, V Thermoplastic composites represent the next-generation core approach to lightweight design. This paper provides a comprehensive description of the automated manufacturing process for hemispherical components. ATL A complete set of mass-production processes, equipment configurations, and mold design solutions has been developed to address three major industrialization challenges: gap control in hyperbolic surface forming, interlayer fusion, and demolding. The process parameters can be directly implemented on the production line, significantly shortening the prototyping cycle for liquid‑hydrogen storage vessels and supporting the lightweighting upgrade of hydrogen‑energy equipment.

(3) Current Research Limitations

Only a hemispherical segmented prototype was manufactured; full-scale tank hydrostatic and hydrogen permeation durability tests were not conducted; only a single case was verified. 12.7mm Wide prepreg tape, with a non‑widened multi‑specification tow‑placement process; no parallel mass‑production scheme involving multiple layup heads has been investigated.

(IV) Future Expansion Directions

• Complete V Forming of the tank assembly and low-temperature hydrogen permeation and cyclic burst‑resistance durability testing;
• Multi-strand wide-width ATL Process development to enhance the production efficiency of large-scale tanks;
• Implement online real-time laser-based defect monitoring and develop a process‑closed-loop, self‑adaptive layup system.
• Low-cost bio-based PA Research on matrix‑composite forming processes to enhance the environmental sustainability of hydrogen storage tanks.

(5) Industry Insights

V Type‑free‑lined thermoplastic hydrogen storage tanks represent a key technology for lightweight hydrogen storage and transportation; however, the in‑situ forming of hyperbolic spherical shells is significantly more challenging than that of conventional flat components. At the manufacturing stage, it is essential to balance laser heat input with layup speed while optimizing robotic trajectory interpolation to minimize gap‑related defects. Nondestructive pressure‑assisted demolding and end-to-end digital twin technologies constitute the core supporting processes that ensure high yield rates in mass production. Thermoplastic… ATL Automated forming processes are poised to become the mainstream manufacturing approach for high-end liquid hydrogen storage tanks in the future.

Image and Text Guide

Figure 1. Schematic diagram of the simplified single‑cycle shear test. [9

Table 1. SLS In testing ATL Process parameters

Figure 2. ATL Process diagram [10

Figure 3. CAD Model (top left), Tolerance Study (bottom left), and Aluminum Casting (right)

Figure 4. CF|PA11 Cross-sectional structure: The figure above shows… UD Adhesive tape; the figure below shows the one that has been… ATL Processed composite materials

Table 2.  of process analysis SLS Result [11

Figure 5.  Axial cross-section of a hemisphere ( ATL )

Figure 6.  by ATL The company’s manufactured outer-tank composite hemispherical shell (left); (right) digital twin model. [ Heatmap ]