Paper number 1005

DESIGN OF LARGE COMPOSITE STRUCTURES UNDER DYNAMIC LOADS WITH FATIGUE ASSESSMENT

José Sancho Rodríguez

Torres Diseños Industriales, S.A. Carretera de Huesca Km. 9. 31119 Torres de Elorz (Navarra), Spain

Summary

Every day design of machinery parts and structures is becoming more restrictive in the simplifying hypothesis accepted for the calculations. Aeronautical applications have been pioneers in the field of detailed calculations (non lineal buckling of structures, compression strength after impact, etc.). Nowadays even in industrial applications performing quite detailed and accurate analysis both lineal and non lineal is starting to be mandatory. Parts made out with composite materials and with high responsibility are requiring non lineal dynamic calculations from which fatigue assessment is performed. Another important aspect when designing a responsibility part with composite materials, is being capable of predicting with enough accuracy the interlaminar stresses appearing in free edges, holes, changes of number of plies, etc. Conventional calculations using classical theory of laminates are not capable of giving useful results, and even in the case of using higher order approximations, results are strongly dependent on the starting hypothesis of the theory used. A final keypoint in interlaminar assessment is the problem of using a failure criterion as conventional criteria are not always accurate enough to predict the onset of delamination. The present paper presents the experience of designing a large composite structure (windmill blade) taking into account all the previous problems (orthotropic laminated material), performing also dynamic non linear and fatigue analysis.

Keywords

carbon fiber industrial applications, non lineal finite element, delamination, fatigue of composites, adhesives, design of composite structures.