Damage Characterization of Nano-Interleaved CFRP under Static and Fatigue Loading

Mohamad Fotouhi,Cristiano Fragassa,Hamed Saghafi,Giangiacomo Minak,Sakineh Fotouhi

doi:10.3390/fib7020013

Abstract

The use of high strength-to-weight ratio-laminated fiber-reinforced composites is emerging in engineering sectors such as aerospace, marine and automotive to improve productivity. Nevertheless, delamination between the layers is a limiting factor for the wider application of laminated composites, as it reduces the stiffness and strengths of the structure. Previous studies have proven that ply interface nanofibrous fiber reinforcement has an effective influence on delamination resistance of laminated composite materials. This paper aims to investigate the effect of nanofiber ply interface reinforcement on mode I properties and failure responses when being subjected to static and fatigue loadings. For this purpose, virgin and nanomodified woven laminates were subjected to Double Cantilever Beam (DCB) experiments. Static and fatigue tests were performed in accordance with standards and the Acoustic Emissions (AE) were acquired during these tests. The results showed not only a 130% increase of delamination toughness for nanomodified specimens in the case of static loads, but also a relevant crack growth resistance in the case of fatigue loads. In addition, the AE permitted to relate these improvements to the different failure mechanisms occurring.

Highlights

Due to their high strength-to-weight ratio and stiffness, carbon fiber-reinforced polymer (CFRP)composites have many applications in different sectors, such as aerospace, superstructure of ships, automotive, civil engineering and even sports goods
This paper reports a good correlation between the mechanical data and recorded Acoustic Emissions (AE) signals that were obtained from the experiments on CFRP interleaved with the Nylon 66 nanofibers under both static and fatigue mode I interlaminar loadings
In the case of fatigue tests, the energy release rates are calculated at the peak value of different numbers of cycles using Equation (1) and reported in Figure 4 in terms of the critical energy release rate that is required for the crack initiation under different numbers of cycles

Summary

Introduction

Due to their high strength-to-weight ratio and stiffness, carbon fiber-reinforced polymer (CFRP)composites have many applications in different sectors, such as aerospace, superstructure of ships, automotive, civil engineering and even sports goods. The following aspects were investigated: the effect of stitching on the strain energy release [1], the improvement on the fracture toughness of laminates by the use of dissolvable thermoplastic [2], the interlayer self-healing and toughening of composites using copolymer films [3], and the relevance of the three-dimensionality on the damage [4]. Different methods, such as matrix toughening, stitching of the plies, and three-dimensional woven fabrics, have been used to prevent delamination [5,6,7,8].

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