ASTM Committee on Composite Materials Approves Compression After Impact Standards
A questionnaire sent to members of ASTM International Committee D30 on Composite Materials proved to be the catalyst for a pair of newly approved standards, D 7136, Test Method for Measuring the Damage Resistance of a Fiber-Reinforced Polymer Matrix Composite to a Drop-Weight Impact Event, and D 7137, Test Method for Compressive Residual Strength Properties of Damaged Polymer Matrix Composite Plates. Both new standards are under the jurisdiction of Subcommittee D30.05 on Structural Test Methods.
According to Adam J. Sawicki, chair, Subcommittee D30.05, D30 members and key industry stakeholders were surveyed in 2002 on their use of existing D30 standards. One of the questions in the survey asked what test methods would be most desirable if standardized by ASTM. “By an overwhelming response, it was made clear that a compression after impact test method was highly desired by the composites industry,” says Sawicki. “To date, the industry has relied on company-specific test methods and a Suppliers of Advanced Composite Materials Association standard that is no longer being actively supported.”
Sawicki notes that D 7136 and D 7137 are the direct result of composite industry demand. “Committee D30 was able to meet the demand by producing two new test standards, which go far beyond the existing industry standard in terms of technical content and guidance, within 18 months of the initiation of the effort,” says Sawicki. “We believe this can serve as an example of how the ASTM standardization process can respond to market-driven demand within a relatively short time period.”
Although one of the key issues involved in compression after impact tests is the separation into damage resistance and damage tolerance, previous standards did not emphasize this separation. This has led to difficulties in properly comparing material behavior. Committee D30 addressed this issue by creating two separate standards, D 7136, which covers damage resistance, and D 7137, which deals with damage tolerance.
Information featured in both standards includes the following:
• Detailed significance and use and interferences sections intended to provide guidance on the use of data in material selection and composite design;
• Detailed reporting instructions for evaluation of the damage state resulting from impact, with references to appropriate nondestructive assessment methods;
• Detailed support fixtures for impact and residual strength testing; and
• Addition of procedures and guidelines for instrumented impact testing.
There are several practical applications to the new standards, including aiding in the selection of advanced composite materials used in aerospace, marine and civil infrastructure applications, and assessments of the ability of a composite to resist damage formation and tolerate the presence of damage. In addition, the standards may be used within “building block” certification programs to better understand the damage resistance and damage tolerance characteristics of composites, to assist in the design and assessment of these properties in more complex configured structures.
“Examples of current programs for which the generation of such data contributes directly to the design include the Boeing 787 Dreamliner and the Airbus A380, both of which are introducing a significant amount of composites into the airframe structure,” says Sawicki.
Committee D30 is seeking participation in future revisions of D 7136 and D 7137. Additionally, a round robin is being planned to develop precision and bias statements for the standards.
Adam J. Sawicki, associate technical fellow, Boeing Co., Philadelphia, Pa.
ASTM staff: Jim Olshefsky
Upcoming Meeting: To be determined; consult Committee D30’s page on ASTM International’s Web site for further details.