Mostapha Tarfaoui

By Yumna Qureshi, Mostapha Tarfaoui, Khalil K. Lafdi and Khalid Lafdi

Composite materials, having better properties than traditional materials, are susceptible to potential damage during operating conditions, and this issue is usually not found until it is too late. Thus, it is important to identify when cracks occur within a structure, to avoid catastrophic failure. The objective of this chapter is to fabricate a new generation of strain sensors in the form of a wire/thread that can be incorporated into a material to detect damage before they become fatal. This microscale strain sensor consists of flexible, untwisted nylon yarn coated with a thin layer of silver using electroless plating process. The electromechanical response of this sensor wire was tested experimentally using tensile loading and then verified numerically with good agreement in results. This flexible strain sensor was then incorporated into a composite specimen to demonstrate the detection of damage initiation before the deformation of structure becomes fatal. The specimens were tested mechanically in a standard tensometer machine, while the electrical response was recorded. The results were very encouraging, and the signal from the sensor was correlated perfectly with the mechanical behavior of the specimen. This showed that these flexible strain sensors can be used for in situ structural health monitoring (SHM) and real-time damage detection applications.

Part of the book: Advances in Structural Health Monitoring

By Hadja Imane Beloufa, Mostapha Tarfaoui, Khalid Lafdi, Mohamed Daly and Amine Bendarma

In this paper, we will be interested in bending tests on a polymer matrix reinforced with graphene nanofillers. The mechanical behaviour and the damage kinetics were determined. The samples were made using controlled dispersions of graphene nanosheets (GNP) in EPON 862 matrix. Various samples with different contents of GNP were made (0, 0.5, 1, 2.5, 5 and 10% by weight). Mechanical properties such as maximum stress, strain at break and Young’s modulus were determined. After each test, the fracture surfaces were characterised using optical microscopy (OP) and scanning electron microscopy (SEM). Experimental results show that the fracture toughness of the GNP/epoxy-based nanocomposites decreases with an increasing percentage of nanofillers. The flexural strength of the samples with 10 wt% of graphene significantly decreased compared to neat epoxy. Based on stress-strain data and the fracture surface analysis, graphene nanosheets seem to impact the mechanical behaviour and the kinetics of the damage. The influences of the weight percentage of GNP on the EPON matrix properties and the performance of the nanocomposites are discussed. In addition, the evolution of bending performance and damage kinetics with graphene content was obtained and analysed.

Part of the book: Advances in Nanosheets