Bolted Joints in Composite Structures: Design, Analysis and Verification. Task II. Test Results--Multifastener Joints
Abstract
Bolted joints are a prime means of load transfer in aircraft components. Compared to other joining techniques, they are reliable and structurally efficient, as well as cost effective. However, bolted joint locations give rise to stress concentrations and could be the source of static and fatigue structural failures. This report presents results from an experimental task that studied the effects of many parameters on composite-to- metal multifastener joints. The parameters addressed included: laminate layup; fastener arrangement; adjacent cut-out; load type; load eccentricity (single versus double shear); fastener head geometry; and test environment. Test laminates were fabricated using unidirectional As1/3501/-6 graphite/epoxy material, and transferred the applied load to aluminum plates. Test results were obtained on many fastener arrangements, including some with a neighboring circular cut-out. Many failures modes were observed and recorded. In some test cases, despite the close tolerances in the specimen hole/fastener geometries, different predominant failure modes were observed in the replicates. A unique fastener load measurement technique, using strain-gaged bolts, was applied to every test case to compute the fractional fastener loads corresponding to the various test conditions. This information, in conjunction with photographic records of failed test specimens will be very useful in validating the strength of multifastener joints which is being developed. Keywords: Composite materials; Load distribution measurement; experimental results; and static loading.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1985
- Accession Number
- ADB099065
Entities
People
- E. Tossavainen
- R. L. Ramkumar