Material Allowables

Material Qualification for Composites

Material qualification for metals used in airframe manufacturing is a mature technology. The designer can take metal properties from a handbook, specify the alloy and heat treatment, and with little or no testing, move on to initial designs for the metallic component.

One of the largest single regulatory hurdles for an airframe manufacturer using advanced composite materials in certified aircraft applications is to generate design allowables that will satisfy Federal Aviation Regulations (FARs). Due to the lack of a regulatory mechanism that encouraged materials users to share data, historically each user has independently executed coupon level test plans and design allowable programs for specific materials for their certification program – a costly and time-consuming process. This has resulted in redundant costs to users, materials manufacturers and regulators.

In an effort to minimize this situation, NASA supported the AGATE and NCAMP projects, which generated traceable design data on the processing, manufacture and use of composite materials.

AGATE—Advanced General Aviation Transport Experiments  This project was initiated 1995 by NASA to promote the use of affordable high performance composite materials in the general aviation industry. Its completion in 2001 signaled the development of an efficient composite material qualification and property data acquisition process.

The “AGATE Method” describes a “standardized” coupon level material qualification test plan and statistical technique that yields lamina design allowables for a specific material system, such that allowables can be shared among multiple users without each user having to repeat the full qualification procedure. Each user needs only to perform a limited “equivalency” test plan to verify that their process yields properties that are equivalent to the original database.

NCAMP Following on from AGATE, NASA supported the creation of a permanent center within the National Institute for Aviation Research (NIAR) at Wichita State University (Wichita, KS), the National Center for Advanced Materials Performance (NCAMP). NCAMP is a continuing project and the data set will continue to grow as more materials are produced, process tested and qualified. The Composites Design data module is kept up-to-date with this new data as it is published.

AdamWorks has extensive material allowable and equivalency data on a number of composite materials allowing customers to achieve a Supplemental Type Certificate or other certification authority approval in putting their composite structures on both military and commercial aircraft.