Accession Number : ADP005004

Title :   Combined Moisture Diffusion and Mechanical Computational Analysis of Composite Bondlines,

Corporate Author : LOCKHEED MISSILES AND SPACE CO INC PALO ALTO CA PALO ALTO RESEARCH LAB

Personal Author(s) : McHugh,S. ; Wadiak,D.

Report Date : NOV 1984

Pagination or Media Count : 8

Abstract : A combined moisture diffusion and mechanical computational analysis methodology was developed as part of an Independent Research program at Lockheed to enhance our understanding of nonlinear and coupled physical processes in materials. The physical behavior of interest is the mechanical response of composite material systems to environmental conditions which can change the materials' moisture content. In particular, it is desirable to know what set of environmental conditions will affect the integrity of a partial adhesive bondline when a bondline gap (no adhesive) is present. The Lockheed proprietary finite element code (DIAL) was modified to analyze this phenomena in two stages: (1) the temporal moisture partial pressures in the materials are calculated from initial and environmental boundary conditions and (2) these partial pressures are then passed to a quasi-static mechanical analysis where the moisture data at each time step is treated as a dilatation (swelling) load. The resultant stress and strain state is then calculated, as well as gap closure, if any. Demonstration of this methodology was on a relatively simple 2-dimensional axisymmetric example problem. The results show primarily compressive stresses caused by the positive dilatation (swelling) induced by moisture intrusion into the structure. The stresses concentrate at adhesive bondlines, and bondline gap behavior (i.e., the absence of a contiguous adhesive bond at material interfaces) is correctly simulated. (Author)

Descriptors :   *COMPOSITE MATERIALS, *STRESS ANALYSIS, MOISTURE, DIFFUSION, MECHANICAL PROPERTIES, ADHESIVE BONDING, MOISTURE CONTENT, STRESS STRAIN RELATIONS, EXPANSION, COMPRESSIVE PROPERTIES, FINITE ELEMENT ANALYSIS, DISCONTINUITIES, STRESS CONCENTRATION, SYMPOSIA

Distribution Statement : APPROVED FOR PUBLIC RELEASE