Enabling Criteria Development for Unitized Composite Structure Joints Containing Textile Reinfored Inserts

Period of Performance: 08/16/1999 - 11/19/2001

$740K

Phase 2 SBIR

Recipient Firm

Materials Research & Design
300 E. Swedesford Rd Array
Wayne, PA 19087
Principal Investigator

Research Topics

Abstract

Recent work involving the use of 3-D woven reinforced inserts as part of the construction of typical airframe joints has demonstrated significant load carrying capability in these joints well beyond the load at which a "first crack" damage has occurred. Despite strong evidence that these preforms offer significant load carrying capability beyond the load causing initial damage, the accepted design approach continues to be to limit the allowable design loads to levels initiating first failure. The development of more intelligent, less conservative joint design criteria, utilizing the reserve strength of such joints could safely remove significant weight from the joints and therefore from the vehicles. To accomplish this, it is necessary to fully characterize joint performance following the "first crack" or when load redistribution occurs in the preform. It is essential that the joint analyst/designer be able to successfully predict the "first crack" load level as well as the subsequent global joint performance. Provided it can be demonstrated that the first crack or damage initiation event is insignificant relative to the performance of the joint under cyclic loading over its lifetime, this analytical capability will allow the design limit load to be set above the "first cracking" load. A program containing analytical tools development coupled with a carefully planned and executed experimental effort is proposed in order to successfully develop new design criteria for joints containing 3-D woven reinforced inserts. Albany International Techniweave will weave the 3-D architecture inserts, fabricate joint subelements, and test the joints in static and cyclic tests. Boeing St Louis and Northrop Grumman El Segundo will each submit joint subelement designs to the program based on JSF vehicle component applications.