Surface Metrology

Surface Finish for Material Bonding for Pressure Suits

Surface Metrology

ME 5841

[ Friday, April 30, 2010 ]

Matthew Doherty

Sidath Wijesooriya

Wai-Mun Leung

1. Introduction

In the design of pressure suits or space suits, there is a combination of soft and hard materials (i.e. fabrics and metals) used to acquire various functions. To reduce the overall size and weight, less of metals used within the design is promoted. In most space suits, an air tight seal requires a gasket or o-ring and two hard elements (stainless steel) compressing the sealing surface and restraining the soft element (fabric material i.e. nylon, Dacron), which is represented in Figure 1 below. In this mechanical bond, a bolt circle is inserted to one of the hard elements and a second hard element to seal against.

Figure [ 1 ]: Cross-sectional Diagram of Typical Air tight seal

The mass and volume increases with more usage of bolts and hard elements which will further increase in the cost of the machining and quality control. One modification is the replacement of bolts and clamps with an adhesion method of bonding the soft element directly on the hard surface to provide the functionality of an air tight seal shown in Figure 2 below.

Figure [ 2 ]: Diagram of ideal method of bonding fabric to metal surface

Bearings and disconnect regions are the preferable regions for bonding sites. To reduce the volume and mass, it would be ideal to bond directly to the outer surface of a hard element such as a bearing or disconnect and maintain the strength and seal currently allowed by the mechanical bond. The method to reduce the volume and mass is to change the type of bond. Instead of the mechanical bond, chemical bond using adhesives may be implemented. The problem occurs when withstanding operating pressures of ~4.7 psi (NASA 1993).

2.1 Objective

Design surface finish to improve the adhesive strength between nylon and aluminum 2024T4. The highest functional...