Title: Shelf Life Quantification & Analysis of Polypropylene-Fabric Parachutes: Macroscopic Approach
Researchers: Professor Alireza Amirkhizi, Vahidreza Alizadeh, Fateme Aghighi
Description: At this point, the main objective of this project is to identify and survey the relevant literature on aging characteristics of LCADS (Low Cost Aerial Delivery System) parachutes, in particular those aspects dominated by the mechanical properties of the canopy cloth under dynamic loading experience during the deployment. The failure of a load drop is not limited to potential damage and observable tear in the canopy due to opening shock. The mission is considered a failure even if the canopy appears undamaged, if it does not open fast enough (or at all) due to change in behavior of the fabric (e.g. stiffening) under deformation rates of interest.
An attempt has been made to estimate the strain rate during the deployment. The procedure for making the samples for high strain rate testing from the available parachute has been investigated. Two material models has been studied in order to simulate polypropylene behavior under different strain rates. The relationship between the initial velocities of the projectile, which hit the folded strip sample, and the strain rate in the strip has been studied for an ideal test to estimate the required initial velocity. Unfolding behavior of parachute has been numerically analyzed to determine the relevant factors for design of the experiment focused on deployment failure.
An extended study is required to observe, quantify, and distinguish the effects of storage and ageing on the stiffness (as related to the opening) and strength of fabric samples, under high rate conditions. Furthermore, a test capable of observation and measurement of relevant properties and mechanisms for opening of polypropylene parachute fabrics to evaluate the effect of shelf storage and ageing need to be designed.