Hui Feng Tan

Preparation and Properties of Shape Memory Epoxy Resin Composites

Kevlar fiber and carbon fiber reinforced shape memory epoxy composites were prepared respectively. The fold-deploy shape memory properties of the composite system were studied at the temperature which was 30°C higher than the glass transition temperature of resin. The results shows that shape fixed rate and shape recovered rate of the composites are decreased with the increase of Kevlar and carbon fiber volume. The shape fixed rate of Kevlar fiber reinforced shape memory composite is higher than that of carbon fiber reinforced shape memory composite, but the shape recovered rate of the former is much lower than the latter.

The Research Method and Performance Analysis of the Curing Process of E51-593 System and TDE85-593 System

As the pre-research of analysis and performance characterization of resin system curing process in space environment, this paper designed the research method for resin system curing process research, and taking epoxy E51 and TDE85 as research objects, did the verifying experiment about the research method in terrestrial environment. The verifying experiment confirmed the feasibility of the research method, and got the conclusion that the results came from DSC and FTIR are not exactly consistent, the method of FTIR is more suitable for curing degree testing in the curing process. The mechanics performance testing showed that the rupture properties of tensile fracture surface of two systems chosen in the experiment evolved from brittle fracture to ductile fracture and the toughness of TDE85-593 was better than that of E51-593.

Dynamic Testing and Analysis of Inflatable Beams

Dynamic testing of an inflatable beam has been performed to evaluate structural natural frequencies and modal damping ratios. The inflatable beam has a pattern of six composite fiber strips inside thin-film structure that increases its local stiffness that the structure can be self-supporting in the gravity environment when the internal pressure is released. A measurement setup was installed, and the dynamic testing was performed in this self-supporting state. Dynamic characters of the beams were tested with internal pressure or not when the beam had a 2.0kg mass on the top. Moreover, the dynamic characters before rolled up were contrasted to one after. The experimental results indicate that the self-supporting inflatable beams had better bending stiffness, and the curl folding process had an impact on the dynamic characteristics of the inflatable beam. The pressure affection is not obvious on dynamics of the beam.

Aerodynamic Analysis of Inflatable Membrane Aeroshell

With continuous developments of the manned space flight and planetary exploration missions, a new inflatable re-entry aeroshell becomes one of the hot topics of international research. It has the obvious advantages of the easy package, light weight, large resistance area, the low coefficient of ballistic, and the small heat generated by hypersonic air. This vehicle can provide a new way for the emergency return of astronauts, deep space instrumentation and payload recovery. This paper focuses on an inflatable membrane aeroshell with a single loop. Three kinds of cone angle of 75 degrees, 90 degrees and 105 degrees are respectively studied aerodynamic drag. These results show that aerodynamic drag is relationship not only with cone angle but also aerodynamic configuration.

Shape Recovery Characteristics of Shape Memory Polymers Subjected to Bending

Shape recovery is a critical characterization of the Shape Memory Polymers (SMP); so far, there has not been a set of uniform specifications, however, on the deformation recovery characterization of SMP, more exactly, on the shape recovery ratio measurement. A simple and effective experimental method is designed to obtain the shape recovery ratio of SMP; and a series of experiments are carried out to measure the shape recovery ratio of a thermoset shape-memory epoxy resin within the finite bending deformation at various test temperatures. And the results show that the shape recovery ratio and rate of the thin sample are larger than that of the thick one; the deformation curvature has little effect on the shape recovery ratio with the test temperatures over, or below, the glass-transition temperature, Tg, but has significant effect near Tg. The conclusions provide an important basis for the structural design of SMP.

Research on Equivalent Bending Stiffness of Conical Inflated Beam

The conical inflated beams have steady bending stiffness before wrinkles appear according to experimental load-deflection curve, then the deflection distribute function is derived based on the differential function of deflection with variable bending stiffness. The equivalent bending stiffness is presented while the conical inflated beam equates to cylindrical inflated beam, according to the deflection formula of beam, the model of equivalent bending stiffness of conical inflated beams is obtained. Comparing the equivalent bending stiffness of conical inflated beams between theoretical model and Experiment results, it is found that they agree with each other well.

Simulation for Gas-Membrane Interaction of Folded Membrane Tubes during Inflation

It is very important for gas-membrane interaction between compressible ideal gas and elastic membrane structure of space folded tubes during inflation deployment. This paper analyses gas flow field of the folded tube by the finite volume method, and simulates inflation process of the membrane tube with different height of the baffle. A finite volume model of gas flow field is established in the folded membrane tube, and variations of the pressure inside the membrane tube are obtained with height of the baffle and inlet flow rate. And then, the gas-membrane interaction is calculated by couple the CFD and CSD solver. The results show that the pressure on the membrane wall increases with the inflation velocity, and inlet velocity of inflation gives rise to the vibration of the membrane.

The Two-Stage Curing Method for Shape-Memory Materials

In this paper, a various shape-memory materials had been prepared by two-stage curing method. The purpose of using this approach was to maintain the excellent shape memory properties and low glass transition temperature (Tg) of shape-memory materials after first stage curing, furthermore, improve the Tg and heat resistence effectively after second stage curing. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and fold-deploy shape memory tests were used to characterize the feasibility of two-stage curing, thermodynamics properties and shape memory performance of these polymers. DSC results showed that two different curing stages could be achieved successfully, DMA results suggested that heat resistance of materials had been improved after second curing stage, while the fold-deploy shape memory tests proved that the composites possessed excellent shape memory properties, it could be deformed into different shape and recovered its original shape fully within three minutes.

Deformation Measurement of an Inflatable Reflector Using Digital Image Correlation

Inflatable antenna is a potential technique for large space deployable antenna and knowing its reflector’s deformation behavior is quite important for its accuracy improvement. A 1.5m-diameter inflatable reflector’s deformations at different internal pressures are studied using digital image correlation(DIC) in the paper. Because of the symmetry of the reflector, only two representative gores on the reflector are chosen to study. During the digital image correlation measurement, some article random dot patterns are drawn on the reflector’s surface. The 2D and 3D displacement maps of the reflector at different internal pressures are gained by DIC measurement and the cross-section of one gore of the reflector according to the internal pressure are analyzed from the measurement results.

Fold-Resistant Characteristics of the Laminate Composites for Flexible Structure

There is considerable interest in the use of flexible laminate composite materials to improve the deployable structures for space applications. Critical to acceptance of these materials is the ability to achieve high packaging strains without damage. However, there does exist more or less damage during the process of folding and unfolding for the laminate composites. Better understanding of folding damage, therefore, is needed for the design of laminate composites and folding pattern. In this work we present a study on the fold-resistant characteristics of two different laminate composites, which were fabricated by covering the aramid fiber/epoxy and carbon fiber/epoxy prepregs respectively with polyimide film on both sides. The results of tensile tests on 3-layer structure laminate composites show that the fold-resistant properties of aramid fiber/epoxy composites could be improved with increasing of the resin content and decreasing of the fiber bundle diameter. For carbon fiber/epoxy composites, the effects of resin content and fiber bundle diameter on reduction rate of fracture strength were more complex. There existed a best range of resin content and fiber bundle diameter. The microscopic observations show that folding resulted in piling up of resin and damage of reinforcing fiber, which would decrease the mechanical properties.