INVESTIGATION OF FATIGUE FAILURE INITIATION AND PROPAGATION IN WIND-TURBINE-GRADE WOOD/EPOXY LAMINATE CONTAINING SEVERALVENEER JOINT STYLES

FROM THE NASA/DOE MOD OA WIND ENERGY RESEARCH PROGRAM CAME THE FINDING THAT LAMINATED WOOD/EXPOSY COMPOSITE IS A LOW-COST CONSTRUCTION MATERIAL THAT MAY WITHSTAND THE LONGTERM SEVERE FATIGUE ENVIRONMENT OF THE ADVANCED WIND TURBINE BLADE. INCREASED ERRICIENCY AND RELIABILITY REQUIREMENTS PLACED ON THE NEXT GENERATION OF WIND MACHINES WILL CHALLENGE DESIGNERS, DEMANDING THEIR UNDERSTANDING OF THE MECHANISMS BY WHICH FAILURES ORIGINATE AND PROPAGATE IN SUCH COMPOSITES. PREVIOUS TESTING OR WOOD/EPOXY LAMINATES HAS SHOWN THAT THE JOINTS BETWEEN THE INDIVIDUAL VENEER SHEETS WITHIN THE LAMINATE ACT AS FAILURE INITIATION SITES WHICH LIMIT ITS LOAD-CARRYING CAPACITY. THE DETERIMENTAL EFFECT OF THESE JOINTS IS MOST FELT IN HIGH-CYCLE FATIGUE, WHICH IS OF KEY IMPORTANCE FOR RELIABLE, LONG LIFE WIND TURBINE COMPONENTS SUCH AS BLADES. THE STUDY OF HOW A MATERIAL BEHAVES UNDER REPEATED STRESS AROUND THE SITE OF A WELL-DEFINED, BUILT-IN DEFECT IS A TRADITIONAL METHOD IN MATERIALS SCIENCE FOR GAINING INSIGHT INTO FATIGUE-RELATED PROCESSES. THE PHASE I RESEARCH WILL ADVANCE THIS TECHNIQUETHROUGH IMPLEMENTATION OF A MOST HIGHLY INTEGRATED FATIGUE TEST MATRIX. THIS UNIQUE MATRIX WILL ALLOW ANALYSIS TO FOCUS SOLELY ON THE EFFECTS OF WELL-DEFINED SAMPLE DEFECTS IN THE FORM OF SEVERAL TECHNICALLY FEASIBLE VENEER SPLICE JOINT STYLES.