Strength Tests
This document contains the results of strength tests conducted on March 20, 2024, on 40D nylon materials and the seams used in a sewn main and pilot parachute.
Test Procedure
The tests were carried out on an MTS Bionix Servohydraulic Test System. The measurement methodology involved placing the ends of each sample in the machine’s grips, followed by clamping them with an appropriately selected clamping pressure. Once prepared in this way, the samples were stretched by the machine [Figure 1] until the point of rupture.
The materials tested included 40D nylon fabrics used in parachute construction, the seams joining fabric pieces, and the load-bearing webbing.
List of Samples
The English translation is:
2.1 Polypropylene Load-Bearing Webbing (Pilot Parachute) and 2.1 Loop-Stitched Load-Bearing Webbing (Pilot Parachute)
2.2 Two Fabric Panels Sewn to Load-Bearing Webbing (Main Parachute):
a) View from the webbing side
b) View from the seam side
2.3 Two Fabric Panels Sewn to Load-Bearing Webbing (Pilot Parachute):
a) View from the webbing side
b) View from the seam side
Measurement Results
a) Summary of Strength Test Results for Pilot Parachute Seams
The average force at Rupture of the connection is 292.1 (±14.3) N.
The standard deviation is 47.3 N.
b) Summary of Strength Test Results for the Drogue Material
The Rupture force of the material used to make the Drogue is 317.6 N.
c) Summary of Strength Test Results for Main Parachute Seams
The average rupture force of the Main parachute seam samples is 310.3 (±24.5) N, with a standard deviation of 59.9 N.
e) Summary of Strength Test Results for the Webbing Used in Parachute Construction
The average force at webbing rupture is 2.762 (±0.081) kN, with a standard deviation of 0.115 kN.
f) Summary of Strength Test Results for Sewn Webbing Connections
The average force at rupture of the sewn webbing connection is 0.92 (±0.134) kN, with a standard deviation of 0.232 kN.
Conclusions:
4.1 The test results of the samples from Figure 7 show that the quality of the seam joining the material has a key impact on overall material strength. The seam creates local stress concentrations caused by notches—the needle holes—which reduce the tensile strength of the entire assembly. Rupture occurred at the stitched area, not in the continuous part of the material. This indicates that the seam is the most vulnerable point of the entire parachute.
4.2 The difference between two fabric strips sewn to the load-bearing webbing in the Main parachute and the ripstop material alone is approximately 50 N, or about 15%. This difference results from the reasons described in conclusion 4.1. A similar comparison cannot be made for the material used in the Pilot parachute, as only one tensile test of the material alone was performed. However, judging by the rupture location of the samples sewn to the webbing, a similar relationship is likely.
4.3 The ripstop materials and their seams in both cases exhibit similar tensile strength, but as noted in section 3.A, the quality of the seam plays a significant role. The most durable material among those tested is the load-bearing webbing, which is about three times stronger than the “loop-stitched” connection.
This article was made possible thanks to the collaboration with the PWr in Space Student Research Group, operating under the patronage of Wrocław University of Science and Technology.
