Future State: How the Micro-scale Combustion Calorimeter is Changing Heat Release Characterization

Abstract

Heat release testing of non-metallic raw materials is performed at The Boeing Company during Quality Assurance (QA) Receiving Inspection to ensure that requirements have been met before parts can be fabricated. Over the past several decades the prescriptive method for characterizing heat release has been the Ohio State University (OSU) method. However, one significant drawback of OSU testing is that test coupons are typically configured as composite panels containing both prepreg and honeycomb core. The addition of the core to the coupon construction adds a source of variation to the OSU test results that can hide the true batch to batch variation of the prepreg material. The addition of the core as well as the processing of the composite panel also adds cost. For prepreg with Payloads Interior applications this cost can exceed $200k annually.

Over the past 10 years a new methodology for QA heat release characterization, the Micro-scale Combustion Calorimeter (MCC) method, has been developed. The MCC method can directly characterize the heat release properties at the material level, thus avoiding some of the sources of variation arising from tests that use the OSU method.

MCC is a bench top test method that typically affords useful information on key flammability properties such as heat release capacity, ignition temperature, heat of combustion, and the amount of material charring generated during combustion. In addition, a new MCC test parameter, the Fire Growth Constant (FGC), has been developed and is showing promise as a sensitive measure of the impact that small material component changes might have on heat release.

In order to support more efficient testing Boeing has developed a user-friendly data visualization software package for the reduction of MCC raw data that facilitates the characterization of materials for their Quality Assurance (QA) heat release properties. The MCC data reduction software has also been licensed by one of the MCC manufacturers, Deatak LLC, and is proving to be a convenient method for both engineering and QA heat release testing. Boeing is now poised to replicate this testing technology with raw material suppliers, which will support a future state of Supplier Delegated heat release testing for prepreg materials with Payloads Interior applications.

Recent studies have also shown that heat release is an additive property of non-metallic composite materials that can be characterized using the MCC method. The results from these studies are promising and point to the development of heat release libraries of raw materials. Searchable libraries would in turn provide designers with accurate heat release estimates for new material configurations.

About the Speaker

Dr. John Harris is an Associate Technical Fellow within the Boeing Research and Technology organization and has been with The Boeing Company for over 22 years. His initial work was focused on the design and development of a luminescent coating system that is still being used to record the distribution of pressure across aerodynamic surfaces during wind tunnel airflow. Later projects included developing heat resisting material systems for the 787 program as well as thermoplastic or elastomeric materials for a variety of aerospace applications. He has been awarded 19 patents for material and process inventions with aircraft applications and is currently supporting Material and Process technologies with Payloads Interior applications.