Novel architecture for anomalous strengthening of a particulate filled polymer matrix composite

Abstract

We propose an architecture for dramatically enhancing the stress bearing and energy absorption capacities of a polymer based composite. Different weight fractions of iron oxide nano-particles (NPs) are mixed in a poly(dimethylesiloxane) (PDMS) matrix either uniformly or into several vertically aligned cylindrical pillars.These composites are compressed up to a strain of 60% at a strain rate of 0.01 s À1 following which they are fully unloaded at the same rate. Load bearing and energy absorption capacities of the composite with uniform distribution of NPs increase by $50% upon addition of 5 wt% of NPs; however, these properties monotonically decrease with further addition of NPs so much so that the load bearing capacity of the composite becomes 1/6 th of PDMS upon addition of 20 wt% of NPs. On the contrary, stress at a strain of 60% and energy absorption capacity of the composites with pillar configuration monotonically increase with the weight fraction of NPs in the pillars wherein the load bearing capacity becomes 1.5 times of PDMS when the pillars consisted of 20 wt% of NPs. In situ mechanical testing of composites with pillars reveals outward bending of the pillars wherein the pillars and the PDMS in between two pillars, located along a radius, are significantly compressed. Reasoning based on effects of compressive hydrostatic stress and shape of fillers is developed to explain the observed anomalous strengthening of the composite with pillar architecture.

Recently emerging trends in thermal conductivity of polymer nanocomposites

“…The main mechanism of heat dissipation in polymers is attained by phonon transfer , Li and McGaughey, 2015, Idumah and Hassan 2016b, Regner et al 2016. Phonons transport heat energy by interacting with each other and with subatomic particles (Reddy et al 2015, Regner et al 2016. Imperfections in the polymer lattice such as dislocations, impurities, and voids have capabilities of introducing irregularities resulting in phonon scattering (Santos et al 2013, Kamseu et al 2015.…”

“…Thus, in order to ensure efficient operational performance of these devices, the unwanted heat generated needs to be rapidly dissipated. The possession of high thermal conductivity is essential for effective dissipation of heat to enable the optimum performance temperature of devices to be kept at very low levels so as to eliminate dielectric degradation caused by overheating (Ngo and Byon 2015, Reddy et al 2015, Regner et al 2016. Hence, the enhancement of heat dissipation abilities of materials used in these sensitive devices has become very crucial (Lee et al 2012a,b).…”

Capacitive behavior of carbon nanotube thin film induced by deformed ZnO microspheres

“…Z 0 is the internal impedance of the material with A 1 , A 3 and c 1 as positive constants and A 2 a negative constant. In a previous study, Reddy et al showed that there is non-linear dependence of stress-strain in PDMS foam-like structures [57]. It can be concluded that the non-linear response is due to the PDMS structure of the device but not the characteristics of the device.…”