Effects of vertically aligned carbon nanotubes on shear performance of laminated nanocomposite bonded joints

Abstract

The main objective is to improve the most commonly addressed weakness of the laminated composites (i.e. delamination due to poor interlaminar strength) using carbon nanotubes (CNTs) as reinforcement between the laminae and in the transverse direction. In this work, a chemical vapor deposition technique has been used to grow dense vertically aligned arrays of CNTs over the surface of chemically treated two-dimensionally woven cloth and fiber tows. The nanoforest-like fabrics can be used to fabricate three-dimensionally reinforced laminated nanocomposites. The presence of CNTs aligned normal to the layers and in-between the layers of laminated composites is expected to considerably enhance the properties of the laminates. To demonstrate the effectiveness of our approach, composite single lap-joint specimens were fabricated for interlaminar shear strength testing. It was observed that the single lap-joints with through-the-thickness CNT reinforcement can carry considerably higher shear stresses and strains. Close examination of the test specimens showed that the failure of samples with CNT nanoforests was completely cohesive, while the samples without CNT reinforcement failed adhesively. This concludes that the adhesion of adjacent carbon fabric layers can be considerably improved owing to the presence of vertically aligned arrays of CNT nanoforests.

Novel Heating Elements for Induction Welding of Carbon Fiber/Polyphenylene Sulfide Thermoplastic Composites

“…It seems that the nanomaterial clusters (dark spots at the interface) created after the HE was damaged are embedded into the resins at the interface and its vicinity. Unlike stainless steel mesh which may cause stress concentration and create voids, the embedded nanomaterial clusters might contribute to the mechanical improvement of the joints, as it is suggested by the LSS results. Similar to the case of HE#1‐serie3, the resin diffusion and the presence of dark spots possibly due to rupture of the HE into small fragments was observed for the HE#2 (Figure b,e).…”

Generally cylindrical orthotropic constitutive modeling of matrix-filled carbon nanotubes: Transverse mechanical properties and responses

“…A close examination of the final exact solutions for displacements, strains, and stresses, that is, equations (12) to (15) show that all of them were derived in terms of material properties, tube geometry, and external uniform radial pressure. Therefore, given the properties and dimensions of the constituents, these analytical closed-form solutions can be used to exclusively obtain 3D results for displacements, strains, and stress distributions throughout any two-phase composite cylindrical tube subjected to an externally applied uniform radial pressure, p. Next, Hook's law was used to derive the formulae for effective radial Young's modulus and Poisson's ratios.…”

“…To obtain the explicit closed-form solution for the effective radial Young's modulus, the average radial and circumferential stresses and average radial strain were found first. Substitution of the stress solutions from equations (15) and (16) into the basic definitions provided in equations (19) and 20, after some mathematical integration, yielded the average circumferential and radial stresses as follows…”

“…Hence, the CNTs will constrain the free elongation of the inner material, leading to the Figure 8. Axial stresses of radially loaded two-phase nanocomposite cylindrical model obtained from (a) finite element analysis and (b) analytical solutions given by equations (15) and (16).…”

“…The circumferential stress had a very low compressive value at the region of the inside matrix and then suddenly jumped to a much larger compressive stress at the interface with the Figure 9. Circumferential stresses of radially loaded two-phase nanocomposite cylindrical model obtained from: (a) finite element analysis and (b) analytical solutions given by equations (15) and (16). Figure 10.…”