ASTM International’s (West Conshohocken, Pa.) Committee D30 on Composite Materials is developing a new standard, ASTM WK30231, titled “Practice for Damage Resistance Testing of Sandwich Constructions.” The proposed practice will be the first industry standard to cover this topic. WK30231 is under the jurisdiction of Subcommittee D30.09 on Sandwich Construction, part of ASTM International Committee D30.
Adam Sawicki, a technical fellow at The Boeing Co. (Chicago, Ill.) and the vice chairman of D30, says the committee has published standards for damage-resistance testing of composite laminates (ASTM D6264 and ASTM D7136), but it does not have analogous standards or standard test methods for sandwich constructions, despite the fact that the latter are a common composite structural configuration.
Sawicki notes that existing standards ASTM D6264/D6264M, “Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer-Matrix Composite to a Concentrated Quasi-Static Indentation Force,” and ASTM D7136/D7136M, “Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a Drop-Weight Impact Event,” are not strictly applicable to sandwich constructions because there are differences in damage modes, inspection methods and other aspects that must be considered. Reportedly, ASTM WK30231 will provide instructions for modifying the test methods in ASTM D6264/D6264M and ASTM D7136/D7136M to determine the damage-resistance properties of sandwich constructions. Sawicki explains, “The properties are required to design sandwich constructions, to demonstrate the structure is sufficiently durable and exhibits no damage or limited damage under specific damage-producing events in service.”
Specifically, the new sandwich damage resistance practice will
- modify static indentation procedures, such as rate of indentor displacement,
- determine a reference impact energy for drop weight impact, appropriate for the sandwich geometry (total thickness, facing thickness),
- characterize indentation geometry,
- discuss appropriate methods for nondestructive inspection and
- provide damage mode characterization.
The standard specimen length and width dimensions, he says, are equivalent to those used for the laminate standards, thus permitting the use of the same fixturing and other equipment for tests of both laminates and sandwich constructions. Provisions will be made to allow alternative specimen dimensions to accommodate the variety of potential sandwich configurations and geometries that might be appropriate for subsequent residual strength testing. “There is a complimentary effort now underway to develop a standard sandwich residual strength test method,” he adds.
ASTM welcomes participation in its standards development efforts. Parties interested in ASTM WK30231 should visit www.astm.org/JOIN.