## 1 Introduction
Our previous studies involved blade-containment tests using a high-speed rotor spin tester to investigate the containment and failure mechanisms of a composite casing [33]. Furthermore, to study how projectile shape affects the outcome, we used testing [34; 35] and numerical methods [36; 37] to compare the impact response and damage evolution of triaxial braided composites for failure events involving blade-like and cylindrical projectiles of the same cross-section perimeter. In addition, [PERSON] et al. [2] used a plate-shaped titanium alloy projectile in experiments on 2D triaxially braided composites and followed up with numerical parametric studies using a multi-scale finite-element model [38] to examine how projectile deflection angle affects impact failure. Considering that a carbon-fiber-reinforced fan casing is always accompanied by a composite fan blade [39; 40], carbon-fiber-reinforced plastic (CFRP) should also be considered as a potential impactor. Thus, significant benefit is expected from studying the dynamic response of triaxial braided composites impacted by a CFRP projectile and how these impacts differ from those involving metal and gelatin projectiles. However, no research on this subject is yet available in the open literature. During operation, composite casing is subjected to different ambient temperatures, which may vary from as high as 100-150 \({}^{\circ}\)C to as low as \(-\)50 \({}^{\circ}\)C. Several studies have considered how environmental temperature affects the properties of resin matrix composites, mainly in the case of low-velocity impact. The composite stiffness decreases substantially with increasing temperature, which increases the absorbed energy and peak deflection, causing extensive damage to the specimens [41; 42]. [PERSON] et al. [43] experimentally determined the low-velocity impact characteristics of woven carbon-fabric-polyphenylenesulfide laminates at 95 and 125 \({}^{\circ}\)C. The results reveal that increasing the temperature decreases the stiffness and delamination area and amplifies permanent indentations. Upon increasing the temperature, the failure mechanism transforms from a brittle to a ductile manner. Temperature is closely associated with plastic deformation of the matrix and its coupling with the resin-rich regions and the fiber-bridging mechanism that stems from the specific weave architecture. [PERSON] et al. [44] reported that the reduced stiffness and strength is due to softening and plastification of the epoxy matrix, debonding at the fiber-matrix interface, and increased interfacial stress in the re-solidified matrix. [PERSON] [45] investigated how temperature affects the multi-impact performance and reported that the number of impacts to failure depends strongly on the temperature because of the global properties of the matrix. The effect of low temperature on triaxial braided composites is another rarely studied subject. [PERSON] et al. [46] carried out low-velocity impact experiments on E-glass-epoxy composite laminates at both sub-zero and elevated temperatures, and the results indicate that temperature more strongly affects the perforation threshold energy of thicker laminates because of increased laminate rigidity at low temperature. [PERSON] et al. [47] investigated how glass-fiber-reinforced polymer composites respond to low-velocity impact under cryogenic conditions. Finally, [PERSON] et al. [48] performed high-speed impact experiments on CFRP at cryogenic temperatures. However, no studies have yet reported how environmental temperature affects the impact response of triaxial braided composites, which poses a threat to the safety of aero-engines. From the above analysis, it can be seen that there are still two challenges in the safety research of aero-engine 2D triaxial braided composite casing. First of all, the fly-off blades may be made of composite materials or titanium alloys, and there is no corresponding testing data or analysis on the containment capability of the casing to blades made of completely different materials.