FATIGUE EFFECTS OF THERMOPLASTIC HELICOPTER COMPONENTS WITH EMBEDDED DELAMINATIONS

THE USE OF THERMOPLASTIC MATERIALS IN ROTOR COMPONENTS MAY SIGNIFICANTLY REDUCE THE PROBLEM OF DELAMINATIONS AND INCREASE FATIGUE LIFE. HOWEVER, LITTLE IS KNOWN OF THE EFFECT THAT MANUFACTURING FLAWS, IMPURITIES, AND VOIDS HAVE ON ROTOR THERMOPLASTIC COMPONENTS STRENGTH AND STIFFNESS AFTER AN EXTENDED NUMBER OF FLIGHT HOURS. TWO MAIN OBJECTIVES ARE PROPOSED: (1) IDENTIFICATION OF CANDIDATE ROTOR COMPONENTS MOST LIKELY TO BENEFIT BY BEING FABRICATED FROM THERMOPLASTIC COMPOSITE MATERIALS, AND (2) GENERATION OF AN EXPERIMENTAL DATA BASE OF FATIGUE EFFECTS ON THERMOPLASTIC SPECIMENS WITH AND WITHOUT MANUFACTURING DEFECTS. A LITERATURE SURVEY WILL BE CONDUCTED TO FOCUS ON PROBLEMS SUCH AS LOCATIONS OF CRITICAL DELAMINATION AND IDENTIFICATION OF THE CANDIDATE COMPONENTS, CONVENIENCE OF FABRICATION OF CRITICAL ROTOR COMPONENTS WITH THERMOPLASTICS, AND BONDING/JOINING THEM WITH THE REST OF THE ROTOR PARTS. THE EXPERIMENTAL DATA BASE WILL BE GENERATED BY TESTING COUPONS. TO SIMULATE MANUFACTURING DEFECTS UPILEX-S(R) DISKS WILL BE EMBEDDED IN THE COUPONS. TENSION/TENSION FATIGUE S-N CURVES WILL BE CREATED FOR THREE THERMOPLASTIC MATERIALS WITH AND WITHOUT EMBEDDED DISKS TO DETERMINE THE RANGE OF THE CRITICAL DELAMINATION SIZE.