LEO Space Environment Research Articles

Effect of the LEO space environment on the functional performances of shape memory polymer composites

For the first time, shape memory polymer composites (SMPCs) have been exposed in LEO environment by the MISSE-FF platform: two carbon-fiber reinforced laminates with an SMP interlayer were retrieved after 1 year of exposure, and tested on Earth. Microscopy, DSC, FTIR and mechanical tests were carried out on flight and backup samples. Results show that flight samples behaved differently, because of their different orientation on MISSE-FF. The applied deformed shape was partially recovered on the sample with zenith orientation during its exposure, but both flight samples did not show any additional shape recovery on-Earth. The other sample, with wake orientation, froze the non-equilibrium shape permanently.

High velocity impact characteristics of MWNT added CFRP at LEO space environment

In this paper, multi-wall carbon nanotube (MWNT) added carbon fiber reinforced plastics (CFRP) composites are suggested as solutions to improve the impact energy absorbing capability of CFRP for spacecraft application because it was proven that the resistance against LEO environment and the quasi-static material properties of CFRP can be improved by adding MWNT in previous papers. To verify the effect of MWNT on the impact energy absorbing capability of composite materials, normal CFRP and MWNT-reinforced CFRP were prepared and tested by using a two-stage light gas gun that can accelerate an aluminum ball of a diameter of 5.56 mm to 1 km/s. And the applicability of MWNT against hypervelocity impact of space debris was studied. In addition, accelerated ground simulation experiments were performed for each material model to simulate the aging of composite materials to verify the effect of LEO environmental aging on impact absorbing capability of composites. For the aging experiment, the impact specimens were simultaneously exposed to high vacuum, atomic oxygen, ultra violet light, and thermal cycling. After being exposed to simulated LEO environment, high velocity impact tests were performed for each material. As a result, MWNT did not have a significant improvement on the impact energy absorbing capability of CFRP under high velocity impact, even though the quasi static material properties are improved by adding MWNT. This is caused by the early generation of fiber breakages on the impact surface before enough generation of progressive failure which is one of the impact energy absorbing mechanism. Similarly, MWNT has less effect on the impact energy absorbing capability of CFRP under LEO environment.

Microstructure Evolution of 2024 Aluminum Alloys Subjected to Thermal Cycling in Simulated LEO Space Environment

The microstructures and properties of 2024 aeronautical aluminum alloy subjected to thermal cycling were investigated in simulated Low Earth Orbit space environment. The experimental results demonstrate that the microhardness of aluminum alloys changed with the increasing of thermal cycles. The results of X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the property changes of the 2024 aluminum alloys during the thermal cycling period are closely related to the microstructural evolution. The relationship between the microstructural evolution and the thermal fatigue was also discussed.

Hypervelocity impact on carbon/epoxy composites in low Earth orbit environment

This paper describes the hypervelocity impact phenomenon on the spacecraft composite bumper especially when the incidence angle is oblique in nature. Three different kinds of specimens namely Al6061-T6, carbon/epoxy non-aged and aged under low Earth orbit environment were manufactured, tested, and validated in this research. These composites were manufactured with 16 layers of CU125NS with the stacking sequence of [(0/±45/90)2]s using autoclave by adopting standard procedures. Afterwards, the specimens were exposed to LEO space environment with UV light, atomic Oxygen, high vacuum, and thermal cycling. The specimens were then impacted by Al2017-T4 spherical projectiles 5.56mm in diameter and, 0.25g in weight within the velocity range of 1000±100m/s. Due to LEO environment exposure, a total mass loss of 0.42% was found in the composites along with degradation in other mechanical properties because of the synergistic effects of UV and AO. The specific energy absorption of the composites was found to be 7% greater than that of Al6061-T6. Secondly, with the increase of incidence angle obliquity, the energy absorption by the composites also increased exponentially. In the end, C-SCAN study was done to evaluate the impact surface and its failure. On the basis of these findings, oblique composite bumpers are suggested as effective spacecraft shielding.

Tissue Equivalence Correction in Silicon Microdosimetry for Protons Characteristic of the LEO Space Environment

The tissue equivalence of solid state silicon detectors in proton radiation fields was determined to improve the radiation protection applications of silicon detectors in aviation and space missions. The study was performed by means of Geant4 simulations. Results are presented showing that a simple c( ~ 0.56) of linear dimensions is adequate to convert experimentally obtained microdosimetric energy deposition spectra in silicon to equivalent microdosimetric energy deposition spectra in water.

Polymerization Process of an Inflatable Composite Balloon in LEO Space Environment

Article Polymerization Process of an Inflatable Composite Balloon in LEO Space Environment was published on June 1, 2000 in the journal Science and Engineering of Composite Materials (volume 9, issue 2).