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

The proposed Phase I effort is aimed at the development of damage tolerant design and failure criteria for joints containing 3-D weave reinforced inserts in composite structures. Recent work involving the use of textile reinforced inserts in the contraction of typical airframe joints well beyond the load at which damage is initiated. Current design practices are conservative and do not allow joints to be loaded beyond first cracking loads. The ultimate goal of this effort is to generate new damage tolerant design guidelines for joints of this type which utilize their strength reserves. This will allow the overall weight of airframes constructed using these joints to be significantly reduced. A combined analytical and experimental program is proposed here. The analytical portion will be performed by MR&D using technically mature micromechanical tools and public domain finite element stress analysis codes. Existing experimental data on joints with textile reinforced inserts available from the AFRL/VAS program entitled, mposite Sandwich Structures, edicted results. Additional sub-element joint testing will be performed as required to supplement the database. Albany International Research Company will weave 3-D reinforced inserts and fabricate the sub-element joints. Boeing (St Louis) will assist in identifying design requirements and geometry for two Joint Strike Fighter (JSF) applications, designing composite joint test specimens representative of JSF structural applications, identifying test specimens loading requirements, and in the evaluation of test results.