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Determine Filled-Hole Strength of Composites with New ASTM Standard

When stress engineers create design values for lay-ups used in composite structures, they sometimes require both open-hole and filled-hole strength data.

Aerospace scientists on ASTM Composites Committee D30 recently developed standard testing for filled-hole tension

and compression.

Published this year, ASTM D 6742/D 6742M, Standard Practice for Filled-Hole Tension and Compression Testing of Polymer Matrix Composite Laminates, applies to structures utilizing bolted joints in aircraft, spacecraft, marine structures, and automobiles.

Adam Sawicki, an engineer-scientist with The Boeing Company, Philadelphia, Pa., said, “When we generate design data to size an aircraft, we consider the worst case—filled hole or open hole—and we test both conditions.” Sawicki drafted the standard with input from an ASTM task group of stress analysts from leading aerospace corporations.

The practice supplements open-hole tests in:

• ASTM D 5766/D 5766M, Standard Test Method for Open Hole Tensile Strength of Polymer Matrix Composite Laminates; and
D 6484/D 6484M, Standard Test Method for Open-Hole Compressive Strength of Polymer Matrix Composite Laminates.

The task group based key sections of the standard on fastener torque and clearance issues reported in “Failure Mechanisms in Compression-Loaded Composite Laminates Containing Open and Filled Holes,” by Sawicki, and P. Minguet, Journal of Reinforced Plastics and Composites, Vol. 18, No. 18 (1999). Five studies sponsored by NASA, the U.S. Air Force, the Federal Aviation Administration, and others also influenced the standard’s content.

The standard provides:

• Procedures and measurements necessary for filled-hole testing;
• Guidance on factors influencing filled-hole tensile and compressive strengths;
• Historical references on values likely to be filled-hole vs. open-hole critical;
• A table with examples of common modes in open-hole tension and compression testing covering a variety of failure locations and modes; and more.

For further technical information, contact Adam Sawicki, The Boeing Company, Philadelphia, Pa. (phone: 610/591-2807). Committee D30 meets Oct. 23-25 at Purdue University, West Lafayette, Ind., in conjunction with the American Society of Composites. For meeting or membership details, contact Jim Olshefsky, manager, ASTM Technical Committees (phone: 610/832-9714). //

Copyright 2002, ASTM