Achieving ultra-high thermal conductivity while maintaining the electrical insulation of polymers is highly desirable for many applications such as thermal management and packaging. In this work, polyethylene / boron nitride nanoplatelets (PE/BNNP) nanocomposite film was produced through melt processing followed by uniaxial stretching. Microstructural analysis reveals that the stretched composite film features a co-continuous network structure which consists of oriented lamellae bridged by both stretched polymer chains and aligned BNNPs along the stretching direction. The resulting film exhibit a metal-like thermal conductivity as high as 106 W m −1 K −1 and it is believed that the unique network structure has enabled efficient phonon transfer across the film, resulting in superior thermal transporting performance. This work shines a light on the design and scalable manufacturing of high performance functional polymer-based composites for future thermal management applications.
Parallel stand bamboo (PSB) is a high-quality wood-like bamboo composite. Failure due to cracking is a major concern in the design of PSB components for building structures. The mode-I fracture properties of PSB composite were studied. The wedge splitting method was employed as the test approach. Numerical analyses were conducted to determine the appropriate test specimen dimensions so that valid fracture toughness could be obtained. An R-curve was evaluated in accordance with the equivalent linear elastic fracture mechanics (LEFM) theory. It was found that the initial crack depth ratio should be less than 0.4 for the fracture toughness test. The fracture toughness of PSB is higher than that of commonly used woods, and their fracture behavior is similar, exhibiting quasi-brittle behavior. The R-curve of the PSB exhibits rising behavior until the critical crack length is reached. However, the post-peak R-curve exhibits a descending behavior, contrary to that of quasi-brittle materials, which present a plateau in post-peak crack extension.
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