Young D. Kwon

Dynamics of the Parachute Sling: Testing Procedures and Evaluations

Abstract This paper discusses material science aspects of a parachute sling. During the deployment of a parachute, the sling experiences the impact caused by rapid deceleration of the parachute. To survive this operation, the sling must have sufficient impact resistance in addition to the strength to withstand the tension due to the weight of payload. The amount of energy absorbed by the sling due to the impact was estimated from the dynamic analysis of a parachute. From the results of the dynamic analysis, the key properties required for a sling material were determined and testing procedures to evaluate those properties were established. The experimental evaluation results for two candidate materials are presented.

Dynamics of an Explosion Blast-proof Aircraft Luggage Container. Part I—Deformation Rates

Abstract The mechanical properties of ultra-strong polyethylene fibers of Spectra type exhibit very large strainrate effects. The modulus and strength of these fibers increases with increasing strain-rate. In ballistic impacts involving high deformation rates, the performance of Spectra fiber composites is, therefore, markedly better than predicted on the basis of data obtained at low deformation rate standard testing procedures. To prevent aircraft disasters caused by explosions in the luggage compartments, the Federal Aviation Agency initiated a program to develop an explosion blast-proof luggage container. Based on previous work, Spectra fibers produced by Allied Signal were an obvious choice for this application. The scope of the present study was to determine the deformation rates in a fiber reinforced composite wall of an aircraft luggage container. The simulated blast corresponded to the explosion of a typical terrorist device.

Flammability Evaluation of Spectra(r) Composites Under Exposure to a Turbo-Torch Flame

Abstract Because of an outstanding capability of absorbing mechanical energy, Spectra® fibers are frequently used in damage tolerant composite materials to protect equipment, blast proof aircraft luggage containers, armor, apparatus and/or people against blast and debris of explosion or projectiles. Since Spectra(r) fiber is made of polyethylene which is one of the most thermally stable polymers in the absence of oxygen, it is possible to design composite structures that are suitable for use in applications where prolonged exposure to flame is anticipated. In this paper, we report the findings obtained in a recent study on the development of the flame barrier materials for constructing the turbo-torch flame resistant Spectra(r) composites. A heat transfer analysis was conducted to achieve a better understanding of the dynamics of the flame resistance. It is shown that the general trend in flame resistance behavior of the composite can be predicted from the component material properties and composite const...

Deformation Analysis of Composites Exhibiting Large Strain-Rate Effects

Viscoelastic high modulus composites exhibit excellent impact damage tolerance, a material characteristic which is essential to achieve the survivability of structures and equipment when these are exposed to high speed projectiles, explosions, etc. Relevant properties and characteristics of viscoelastic ultra-high strength polyethylene fiber reinforced composites are discussed to identify their inherent advantages resulting from the strain dependent behavior of the reinforcing .fiber. The focus of this paper is the theoreticalrand experimental deformation analysis of viscoelastic composites involving farge strains caused by a ballistic impact.