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This paper presents a study of thermal management of tablet computers (tablet PCs) using phase change materials (PCMs) encapsulated in aluminized laminated film under continuous operation. The experimental setup consists of original tablet PC parts and a simplified dummy printed circuit board (PCB) with a thermal response similar to the original PCB. Two PCMs were used in the experiments, n-eicosane and PT-37 (a commercial PCM from PureTemp). These PCMs have similar melting temperatures (n-eicosane – 35.6 °C; PT-37 – 36.3 °C) but different latent heats of fusion (n-eicosane – 236 kJ/kg; PT-37 – 206 kJ/kg). Two encapsulations with different sizes (6″ × 2.6″, 7″ × 1.5″) but the same thickness (0.0792″ (2 mm)) were used in this study. The effects of inclination and power input level on the thermal behavior of the tablet were investigated. Experiments showed that PCM encapsulated in laminate film led to lower back cover temperature for constant heat flux applications. As much as a 20 °C temperature reduction of the back cover hotspot was achieved with encapsulated PCM. It was also observed that better thermal behavior was achieved both by the melting of PCMs and heat spreading through the laminate film. It was found that the rate of PCM melting is directly related to the power input. No significant effect on PCM melting and temperature history was observed in relation to the system inclination.

Strength and toughness are two crucial mechanical properties of a solid that determine its ability to function reliably without undergoing failure in extreme conditions. While hexagonal boron nitride (hBN) is known to be elastically isotropic in the linear regime of mechanical deformation, its directional response to extreme mechanical loading remains less understood. Here, using a combination of density functional theory calculations and molecular dynamics simulations, we show that strength and crack nucleation toughness of pristine hBN are strongly anisotropic and chirality dependent. They vary nonlinearly with the chirality of the lattice under symmetry breaking deformation, and the anisotropic behavior is retained over a large temperature range with a decreasing trend at higher temperatures. An atomistic analysis reveals that bond deformation and associated distortion of electron density are nonuniform in the nonlinear regime of mechanical deformation, irrespective of the loading direction. This nonuniformity forms the physical basis for the observed anisotropy under static conditions, whereas reduction in nonuniformity and thermal softening reduce anisotropy at higher temperatures. The chirality-dependent anisotropic effects are well predicted by inverse cubic polynomials.