A STUDY ON AWJ TRIMMING OF COMPOSITE AIRCRAFT STRINGERS

A study was undertaken to develop AWJ processes and tools for trimming carbon fiber composite stringers used in several structural air frame components. The cutting strategy was to trim the stringers flanges from the inside out to allow beveling and to minimize cutting risks. Specially designed small size side fire cutting heads were developed to meet this requirement, and they were first used to cut flat composite material samples with thicknesses up to 1 inch. These cutting tests focused on identifying the cutting speeds for producing high quality surfaces without any frayed edges or delamination and meet the Boeing BAC 5578 specifications. For example, tests were performed to determine the effects of pressure, abrasive flow rate, orifice size, and cutting speed on the taper and surface finish of the produced surface walls. It was shown that cutting stringer material with AWJ is highly feasible both qualitatively and quantitatively. An example cutting rate of 18 inch/min was determined to cut 0.65-inch thick composite to produce better than 400 micro inch surface finish with less than 1 degree taper. Trimming tests were then performed for both 90 and 45 degrees to produce straight and beveled surfaces using sample stringers. This new AWJ process is now being used for production at aircraft subcontractor facilities for the Boeing 787.