This work presents a fundamentally redesigned, liquid-free cryostat concept for the in-situ mechanical characterization of materials under cryogenic conditions based on an existing proof-of-concept work. The primary focus lies on enabling advanced real-time diagnostics at low temperatures, particularly through the integration of optical and acoustic measurement techniques such as digital image correlation (DIC) and acoustic emission (AE) analysis. These methods allow continuous observation of deformation, damage initiation, and crack propagation during testing.
The system is specifically designed to support a wide range of mechanical experiments, including tensile, compression, and shear tests, as well as fracture toughness and crack opening investigations. While the current research focus is on carbon fiber-reinforced polymers (CFRP), the cryostat concept is designed to be versatile and can be adapted to other material classes such as metallic alloys or polymers relevant for cryogenic applications such as aerospace and hydrogen technologies.
At the core of the concept is an optimized thermal architecture based on a two-stage Gifford–McMahon (GM) cryocooler, complemented by an additional single-stage GM cryocooler operating in the temperature range down to 20 K. The redesign aims to significantly reduce cooldown times, minimize thermal gradients within the specimen region, and improve overall thermal load management. To achieve this, the thermal conduction path between the cryocooler and the specimen has been deliberately shortened, reducing thermal resistance and enhancing temperature homogeneity. The additional cryocooler is dedicated to direct specimen cooling, while the primary system intercepts and dissipates parasitic heat loads at higher temperature levels.
In parallel, the mechanical design has been comprehensively revised with respect to stiffness, load-bearing capacity, and thermal coupling, ensuring reliable force transmission under cryogenic conditions. An adapted radiation shielding concept further reduces external heat input. Compared to the currently existing proof-of-concept system, the redesigned cryostat offers substantial improvements in thermal performance, mechanical stability, and experimental accessibility. These enhancements are a key motivation for development, aiming to establish a robust platform for high-precision in-situ cryogenic material testing.

Keywords
Liquid Free Cryostat|Material Testing|CFRP|Digital Image Correlation|Acoustic Emission