**On the Influence of Capillary-Based Structural Health Monitoring on Fatigue Crack Initiation and Propagation in Straight Lugs**

**Marc Moonens 1,\*, Eric Wyart 2, Dieter De Baere 1, Michaël Hinderdael 1, Julien Ertveldt 1, Zoé Jardon 1, Galid Arroud <sup>1</sup> and Patrick Guillaume <sup>1</sup>**


Received: 5 August 2019; Accepted: 9 September 2019; Published: 12 September 2019

**Abstract:** This paper addresses the influence on the fatigue life induced by the implementation of a capillary-based structural health monitoring methodology, patented under the name eSHM. It consists in integrating structurally small and pressurized capillaries into the component, so that when a fatigue crack breaches the capillary network, it results in a leak flow to the open atmosphere and loss of pressure in the galleries which is detected by a pressure sensor. The novelty of the proposed system resides in the opportunity to locate the capillary according to the designer's need, as one resorts to additive manufacturing for the part production. However, the presence of these galleries in highly stressed regions raises concerns about crack initiation at the capillary itself and accelerated fatigue crack growth. This paper aims at the quantification of the influence the eSHM has on the fatigue behavior of the component and the determination whether this influence is significant or not. To that purpose, numerical simulations on a straight lug component, using the finite elements and eXtended Finite Elements Methods (XFEM), are performed. Various capillary sizes and shapes are assessed, so as to enable a general conclusion on the impact of the eSHM methodology in straight lugs.

**Keywords:** capillary-based structural health monitoring; fatigue crack growth; fatigue crack initiation; XFEM; straight lug
