Load Spectrum Effects on Bonded Composite Joints.
Abstract
This report presents the results of an experimental study of the fatigue and residual strength behavior of double lap boron/epoxy-to-titanium bonded joints. The program investigated various effects of load spectrum truncation, frequency, and intensity, and surface ply orientation on specimen endurance at a room temperature, dry environment. Results indicate the sensitivity of fatigue life to the orientation of the plies at the bond surface. Low amplitude loads, approximately lg about the mean, were significant and should not be arbitrarily truncated. Proof loading to 130% of limit load significantly reduced fatigue life even where spectrum loads were of this same magnitude. Fully random load sequencing was found to reduce the endurance or flight-by-flight missions to failure over a contrived but reasonably random spectrum that contained blocked loading (constant amplitude) of low intensity loads. The location of the scrim material on each boron/epoxy ply played a significant role in the strength and failure mode of the joints. The frequency of applying loads was not significant, comparing 1/2 Hz and 8 Hz endurance data. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1977
- Accession Number
- ADA042435
Entities
People
- M. D. Richardson
- R. T. Achard
Organizations
- Flight Dynamics Laboratory