Accession Number:

ADA364745

Title:

Characterization of Materials Degradation due to Corrosion and Fatigue in Aerospace Structures

Descriptive Note:

Final technical rept. 15 Apr 93-14 Oct 98

Corporate Author:

CALIFORNIA UNIV LOS ANGELES SCHOOL OF ENGINEERING AND APPLIED SCIENCE

Personal Author(s):

Report Date:

1999-05-13

Pagination or Media Count:

17.0

Abstract:

Research was carried out in two related areas 1 the degradation in the load carrying capacity of the structural components, and 2 nondestructive evaluation NDE for characterization of the degradation. In the first topic, the effect of pitting corrosion on the strength of aircraft grade aluminum alloys was studied through laboratory tensile and fatigue tests and theoretical modeling. The probability of failure in the presence of multiple pits was found to be strongly affected by certain parameters of the pit distribution. The effect of fatigue and dynamic loading on structural polymer matrix as well as metal matrix composites was also studied both theoretically and experimentally. Certain metal matrix composites were found to perform poorly under transverse loads due to stress concentration effects at fiber-matrix debond edges and at microcracks within the interfacial layers. In the second topic, four relatively new ultrasonic NDE techniques were developed. In the first, a guided wave based technique for detecting hidden corrosion sites in aluminum lap joints was developed. This technique has the potential to improve the effectiveness and efficiency of lap joint inspection significantly. Another technique based on a dual transducer pitch-catch arrangement was developed that can be used for cost-effective characterization of composite laminates. A third technique based on dual contact transducers was introduced for the monitoring of the stiffness degradation of composites during fatigue loading. In the fourth technique a guided wave based acoustic emission method was developed for monitoring micro crack growth from corrosion sites in aluminum and from impact load sites in composites. This technique has the potential for use in detecting the presence of hidden corrosion sites at an early stage of their development in metallic aircraft structures and to monitor impact damage in composite aircraft structures.

Subject Categories:

  • Metallurgy and Metallography
  • Mechanics
  • Aircraft

Distribution Statement:

APPROVED FOR PUBLIC RELEASE