Impact of carbon nanotube defects on fracture mechanisms in ceramic nanocomposites

Abstract

Carbon nanotubes (CNTs) can improve the fracture toughness of ceramic composites. It is widely believed that defects in the CNTs will alter key properties that ultimately dictate composite toughening. However, to date there have been no studies that directly correlate these specific properties to controlled defect levels in CNTs. This type of investigation is presented here, using ceramic nanocomposites with a polymer derived ceramic (PDC) matrix, reinforced with multiwalled CNTs. This work includes basic fracture measurements on full composite films, combined with careful testing of individual CNTs embedded in the same PDC matrix. The defect levels in these CNTs were controlled with high energy carbon ions. By using this approach, it was possible to directly correlate defect levels with the interfacial shear strength (IFSS) of the CNT/PDC interface, the CNT fracture strengths, and the pull-out lengths observed after fracture of the full composites. The radiation induced defects led to substantial increases in the IFSS, and

Research on the interface properties and strengthening–toughening mechanism of nanocarbon-toughened ceramic matrix composites

“…Where Fmax is the maximum measuring force applied to the CNT and l emb is the length of the CNT embedded in the matrix. This formula can provide an effective strategy for improving nanocarbon-reinforced ceramic matrix composites [82]. But in boron nitride sheet, it will result in a sharp decrease in mechanical performance when defect percentage is greater than 1% [83].…”

Mechanical testing of two-dimensional materials: a brief review

“…Most recently, Lou et al [182,183] have designed and developed a micro-fabricated device shown in Figure 15(a), which can perform the tensile testing and pullout experiment [184][185][186][187][188][189]. The microdevice uses a spring-like 'push-pull' mechanism, consisting of three moveable shuttles attached to each other via inclined freestanding beams.…”

Engineering of oriented carbon nanotubes in composite materials

“…On the other hand, bonding at the CNT/polymer interface (covalent, van der Waals) also plays a decisive role to enhance the uniformity of the CNT dispersion into the polymer matrix [ 136 ]. Therefore, to obtain the desired properties of CNT/polymer composites, such as the thermal, mechanical and electrical properties [ 8 , 10 , 137 ], the characterization of surface properties including the CNT surface orientation and surface defects are also important [ 138 – 140 ]. The defects can have both positive (increasing the bonding at the interface and between carbon structures [ 25 , 137 , 139 , 141 ]) and negative (reduction of the quality of physical properties [ 10 , 141 ]) effects on the application and quality of composites.…”