Open-Hole Composite Laminates
A new ASTM International standard will answer industry’s need for guidance in determining fatigue properties of open-hole composite laminates.
D7615/D7615M, Practice for Open-Hole Fatigue Response of Polymer Matrix Composite Laminates, was developed by Subcommittee D30.05 on Structural Test Methods, part of ASTM International Committee D30 on Composite Materials.
The purpose of D7615/D7615M is to provide guidance for the development of open-hole fatigue data for material specifications, research and development, material design allowables and quality assurance, according to Mark Chris, associate technical fellow, Bell Helicopter Textron Inc., and chairman of D30.05.
“The primary property that results from use of the practice is the fatigue life of the test specimen under a specific loading and environmental condition,” says Chris. “Replicate tests may be used to obtain a distribution of fatigue life for specific material types, laminate stacking sequences, environments and loading conditions.”
Chris also notes that D7615/D7615M is particularly useful for developing design factors from relatively small standard coupons to account for the effects of environmental conditions and data scatter that can then be applied to test programs involving larger scale test articles (from structural elements through full scale structures).
“The scale of these larger tests often makes it impractical to perform them at environmental conditions other than lab ambience,” says Chris. “Also, fabricating larger test articles and performing enough test iterations to determine a statistical distribution may be cost prohibitive.”
Primary users of D7615/D7615M will be engineers designing composite structures that will be subjected to cyclic loading in service, where an understanding of the fatigue response is necessary in order to design for the desired margin of safety.
Participation in the ongoing standards development activities of D30 is welcome. “We are particularly interested in any users who have experience in testing, design and analysis of composite materials that may provide additional insight or a different perspective on our standards development,” says Chris.
Technical Information: Mark Chris, Bell Helicopter Textron Inc., Dallas, Texas
ASTM Staff: Ashley Wiand