Development of failure criteria and experimental teseting for composite adhesively bonded scarf repairs utilizing structural paste adhesives

Abstract

Rapid growth of composite application in wind energy has strained the wind turbine blade service industry as blades continually fail prior to life cycle expectations. Minimal research surrounding composite repair has led to gaps in the ability to characterize, analyze, and predict composite repair behavior. Certification standards derived from two dimensional simplified geometric configurations are speculated to be conservative. In this study, coupon level adhesively bonded composite scarf repair specimens are developed and tested to failure under static tensile loads. Based on experimental results, a geometry independent failure criteria is proposed and validated through finite element modeling. Specimen failures are compared against current repair standards and analysis techniques. The proposed maximum Von Mises Strain failure criteria has potential to provide a preliminary decision making framework for the service industry reducing time, cost, and resources.