Speaker
Description
The design and performance validation of composite overwrapped pressure vessels (COPVs), particularly Type-3 and Type-4 cryogenic tanks, are critical for space and defense applications where weight, thermal stability, and pressure resistance must be optimized. Among the most influential process parameters determining composite integrity are the resin-binder ratio, winding orientation, and curing temperature—each affecting the microstructure, interfacial adhesion, and residual stress behavior of the carbon fiber (CF)-reinforced laminate. To systematically study the complex interplay between these variables and to optimize the overwrap configuration for cryogenic performance, this study proposes a Design of Experiments (DoE) approach using the Box-Behnken design (BBD) methodology.
The Box-Behnken design is an efficient, second-order, response surface methodology that enables the investigation of multiple variables with reduced experimental runs compared to full factorial designs. In this study, BBD is employed to generate statistically robust datasets using three independent variables: (1) resin-binder ratio (wt. %), (2) winding orientation angle (±θ degrees), and (3) curing temperature (°C), with the objective of achieving optimal interlaminar shear strength (ILSS) and cryogenic tensile strength. Each experimental condition produces a specified composite thickness, similar to actual tank overwraps. The output responses include strength retention after cryogenic exposure, microcrack density, and visual delamination indices, enabling a comprehensive understanding of how manufacturing parameters influence mechanical performance.
To ensure that the mechanical behavior observed is representative of actual Type-3 and Type-4 cryogenic pressure vessels, this methodology involves winding CF over real metallic (Type-3) or polymer (Type-4) cylindrical liners, followed by controlled curing and consolidation under conditions that replicate real manufacturing setups: including fiber tension control, consolidation force, and dome transition angle geometry. Once cured, the cylindrical COPVs are axially cut into flat coupons to produce tensile specimens with real overwrap architecture. These specimens are subjected to mechanical testing in cryogenic environments using LOX (90 K), LN₂ (77 K), and LH₂ (20 K) as the temperature mediums. The resulting stress-strain behavior provides key insight into crack propagation, delamination patterns, and fiber-matrix interaction under thermal shock and contraction-induced stress fields.
The use of Box-Behnken design in this context offers several advantages. Firstly, it reduces the number of experimental iterations required to understand the main and interaction effects of critical variables, thereby saving material cost, curing time, and liquid cryogen resources. Secondly, BBD enables the generation of predictive models that can interpolate the mechanical performance at intermediate parameter values, making it possible to optimize combinations without exhaustive physical testing. Additionally, this structured statistical approach ensures repeatability and reproducibility, two critical attributes for qualification in aerospace-grade cryogenic vessels.
In a domain where each winding trial and curing cycle can be both time-intensive and cost-prohibitive, the implementation of such a DoE-driven strategy significantly accelerates the R&D cycle, guiding material scientists and process engineers to quickly converge on the most promising configurations. The microstructural analysis of cryogenically fractured specimens, coupled with stress modeling and microscopy, can validate the interfacial performance and predict long-term durability in service conditions.
As a conclusive remark, the experimental framework outlined here offers a cost-effective, scalable, and statistically rigorous pathway to determine the optimal carbon fiber overwrap conditions for cryogenic tanks. By mimicking actual tank construction, it bridges the gap between laboratory coupon testing and full-scale component qualification. This methodology empowers the industry to make data-driven decisions in selecting materials and processes that maximize performance, reliability, and safety of composite pressure vessels under cryogenic conditions. Ultimately, it aids in product translation, reducing trial-and-error costs, and enhancing the commercial readiness of indigenous Type-3 and Type-4 tank technologies for high-stakes applications in aerospace, defense, and cryogenic transport systems.
| Submitters Country | INDIA |
|---|---|
| Are you a student? | No |
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