Penetration Study of Aluminum, Glass Fiber-Reinforced Aluminum Laminate, and Carbon Fiber-Reinforced Plastic
The current high-reach extendable turret (HRET) used to fight aircraft fires is equipped with an aircraft skin-penetrating nozzle (ASPN). The ASPN is a long, hollow, aluminum penetrator with a steel conical tip equipped with machined perforations. In an internal aircraft fire, the HRET forces the ASPN through the fuselage aluminum skin to spray water and/or chemical agents to extinguish the fire. This study investigated the effectiveness of the current ASPN design in perforating aluminum, glass fiber-reinforced aluminum laminate (GLARE), and carbon fiber-reinforced plastic (CFRP) laminate panels, which are used in the newer aircraft fuselage structures. A special test fixture was constructed for testing specimens in 90-degree (normal) and 45-degree angle penetration conditions. Strain and deformation data, as well as fracture patterns, were collected to assess the responses and failure modes of the different material systems. The data were used to validate finite element (FE) models developed during the course of this program for simulating the penetration processes of the three material systems tested.
Results showed that under normal penetration conditions, the force required to penetrate the GLARE laminates were 4, 4.5, and 6.4 times the force required to penetrate the nominal 0.04-in.-thick aluminum alloy used in transport aircraft fuselage. For the three CFRP laminate thicknesses, the required penetration force was 3.3, 4.6, and 4.8 times higher. Comparing the penetration/perforation-resisting forces required for same thickness panels showed that aluminum panels require approximately twice the force than the GLARE and CFRP laminates. It should be noted that while the largest penetration force in aluminum alloy occurs at breakthrough, in the GLARE and CFRP laminates, the largest resisting force occurs at the end of the perforation due to the conical shape of the ASPN. Under the 45-degree angle penetration condition, GLARE laminates require 2.9, 3.8, and 5.4, and CFRP panels require 2.2, 2.2, and 3.5 times higher force to penetrate than the 0.04-in.-thick aluminum laminate. Results indicated that loading rate has marginal effect on the load-penetration behavior of all three materials under both angles of perforation.
DOT/FAA/TC-14/33
Authors: Chris Swin, Prof. Tein-Min Tan, Ph.D., and Prof. Jonathan Awerbuch, Ph.D.