Effect of Total Bonded Area on Hydrodynamic Ram Resistance of a T-Joint

Abstract

Hydrodynamic Ram (HRAM), which occurs due to overpressure created in an enclosed fluid by the transfer of energy and momentum from a penetrating projectile, can be quite destructive to the enclosing structure. Fuel cells are particularly susceptible to HRAM, with the critical damage occurring at the joints. Independent joint testing using a Ram Simulator or RamGun, a device capable of creating HRAM pressure, enables testing of T-joints to assess HRAM resistance. The test chamber is instrumented with a variety of pressure transducers to record the pressure applied to the joint in the chamber. In this study a baseline T-joint is tested using the V50 ballistic testing approach to establish the pressure range required to cause failure of the joint. Additional plies are then added to another joint with the same skin thickness at the skin interface to increase the total bonded area. This modified joint is tested in the RamGun and its resistance to HRAM is examined by studying the pressure required to cause failure. A coarse mesh cohesive zone failure model (CZM) is created of both configurations using Arbitrary Lagrangian Euler (ALE) Fluid Structure Interaction techniques in the commercial software LS-DYNA to predict failure and possible damage attenuation of a full scale fuel cell model that utilizes these two T-joints types. The research indicated that increasing the total bonded joint area increases HRAM resistance of a joint.