Wetometer for Measurement of Moisture in Composites

A combined experimental and analytic approach to moisture diffusion analysis (MDA) has evolved in proof of principle form as a new instrument termed a moisture profilometer .. The objective in moisture profilometry is the quantitative analysis of the spatial distribution of moisture within composites and definition of localized internal stress fields. An electrolytic cell is utilized to record cumulative moisture evolution and moisture effusion rate. Variation of cell geometry accommodates either laboratory analysis of small composite damage control specimens or field inspection of limited surface area of composite structure in an area scanning mode. An important new aspect of moisture profilometry is calculation of the depth profile of moisture concentration from measurement of surface effusion and rate with time. Statistical estimation theory is applied to this problem and preliminary results indicate that concurrent calculations can generate moisture concentration profiles during the course of moisture effusion measurements. Results of initial instrument design and computational analysis will be demonstrated and discussed

Moisture Diffusion Analysis of Composite Strength Degradation

Moisture diffusion analysis (MDA) has been developed as a new non-destructive evaluation methodology to monitor the strength degradation of graphite-epoxy composite materials. Studies of composite strength degradation due to high moisture identify reversible strength loss due to current moisture content and irreversible strength loss related to prior moisture exposure with microstructure damage. MDA measures current moisture content, directional diffusion coefficients, and moisture concentration profiles. MDA measurement utilizes an electrolytic cell to concurrently record cumulative moisture content and moisture effusion rate. Extension of the diffusion analysis of Shen and Springer isolates directional diffusion coefficients and indicates a high sensitivity of MDA to moisture degradation of the fiber-matrix interface. Extension of the methodology to analyze non-Fickian diffusion shows that MDA can be applied to locate regions of composite strength degradation related to hydrothermal cycling effects. Studies which correlate MDA with ultrasonic response, and interlaminar shear strength of composite laminates subjected to localized moisture damage, show that MDA can be applied to map and locate low strength regions of a composite structure

Detection of Hydrothermal Aging in Composite Materials

In the title of this paper the term hydrothermal , meaning separate or combined conditions of high moisture and temperature, is introduced to describe the complex property degradation processes in two graphite-epoxy composites. It became evident in the course of this study that important hydroelastic stresses degrade composite strength in much the same fashion that thermoelastic stresses do. In fact, the study shows that there are complex internal stress effects within the composite, probably concentrated at the fiber-matrix interface, which depend upon the detailed prior history of moisture-temperature exposure

Study program for encapsulation materials interface for low-cost solar array

The service integrity of the bonded interface in solar cell modules used in solar arrays is addressed. The development of AC impedance as a nondestructive evaluation (NDE) methodology for solar arrays is reported along with development of corrosion models and materials selection criteria for corrosion resistant interfaces

Study program for encapsulation materials interface for low cost silicon solar array

An atmospheric corrosion model was developed and verified by five months of corrosion rate and climatology data acquired at the Mead, Nebraska LSA test site. Atmospheric corrosion rate monitors (ACM) show that moisture condensation probability and ionic conduction at the corroding surface or interface are controlling factors in corrosion rate. Protection of the corroding surface by encapsulant was shown by the ACM recordings to be maintained, independent of climatology, over the five months outdoor exposure period. The macroscopic corrosion processes which occur at Mead are shown to be reproduced in the climatology simulator. Controlled experiments with identical moisture and temperature aging cycles show that UV radiation causes corrosion while UV shielding inhibits LSA corrosion