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The use of bonding for joining composite materials in high-performance structures has increased significantly, as this joining method offers improved stress distributions and capability of joining dissimilar materials. However, the use of adhesive bonding for this purpose might lead to delamination failure, caused by peel stresses acting on the generally weaker transverse direction of the composite adherends. This work focused on improving the resistance to delamination of composite adhesive joints by using a novel composite with a reinforced high toughness resin on the surfaces. Single-lap joints using the novel composite material as adherends, were found to have 22% higher failure loads when compared with the specimens using carbon fiber reinforced polymer only adherends, with the failure mode changing from delamination of the adherends to cohesive failure in the adhesive. The lap shear strength was also close to that attained when using high strength steel adherends. A finite element analysis, using cohesive elements, was performed with the objective of reproducing the experimental results and better understanding the failure mechanism. Using this model, it has been determined that the change of failure mode and the plasticity on the surface layers are the two key factors underlying the increase in strength obtained with the novel adherends.

In order to verify roles of interphase played in glass transition temperatures (Tgs) of carbon nanotubes reinforced epoxy resin (CNT/epoxy) composites, three types of interphase were produced between the CNTs and the cured epoxy. It was achieved by selection of pristine CNTs (p‐CNTs), amino groups grafted CNTs (NH2‐CNTs) and hydroxyl groups grafted CNTs (OH‐CNTs) as the reinforcement, respectively. Both dynamic mechanical analysis (DMA) and molecular dynamics (MDs) simulation were conducted to study Tg of the CNT/epoxy composites. The DMA tests showed that Tg of NH2‐CNT/epoxy composites increased, while Tg of OH‐CNT/epoxy composites decreased, compared with p‐CNT/epoxy composites. The MD simulation of the CNT/epoxy composites models explained effects of interphases on Tgs of the CNT/epoxy composites. Tg of the NH2‐CNT/epoxy composites increased with the formation of covalent bonds between the NH2‐CNTs and the cured epoxy. Although Tg of the OH‐CNT/epoxy composites decreased due to the weak interphase, where no such covalent bonds were formed. It can be inferred that the covalent bonds between the CNTs and the polymer matrix is beneficial to increase Tg of the CNT/polymer composites. POLYM. COMPOS., 39:E1129–E1138, 2018. © 2017 Society of Plastics Engineers

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Pinacolborane (PINB) was adopted as a novel boron resource to modify polycarbosilane (PCS) in order to produce a fusible boric precursor for SiC fibers. Several boric PCS (B-PCS) were obtained by varying the reaction temperature and PCS to PINB weight ratio in the reactants. The soft point and average molecular weight of the B-PCS increased after modification and the precursors showed well melt-spinning property validated by a filature experiment. The ceramic conversion process of the B-PCS was studied by thermogravimetric analysis and infrared spectrum method. Although \0.3 wt% of boron was involved, the ceramic yield of PCS was greatly enhanced. Moreover, the crystallization of the boric precursors was obviously blocked at 1400 and 1600°C compared to pure PCS, which make the B-PCS a promising precursor for heat-resisting SiC fiber suitable for massive manufacture.

The application potential of bentonite is closely related to the content of montmorillonite from it, and the purification of bentonite is conducive to expanding its industrial application. In this paper, purification method of Keerjian bentonite with low to medium grade were studied systematically. A comparative study of natural settlement, chemical dispersion and high-speed centrifugation was carried out. In addition, one-factor experiment and orthogonal experiment on a compound purification method, chemical dispersion following by high-speed centrifugation, were conducted. According to the experimental result, the optimal parameters of the compound purification, namely slurry ratio 1:8, dispersant amount 1.2% and soaking time 24h, were obtained. This study solved the problem of low utilization level and low purification efficiency, which shade light in the application of Keerjian bentonite with high efficiency and high economic benefits.