Storage Modulus Characteristics of Magnetoactive Foams Fabricated via Different Approaches

Over the past decade, extensive research on the magnetoactive (MA) foam has drawn significant attention from researchers, inspiring the development of wider range of technologies and applications. MA foam is a smart composite foam where its characteristics can be manipulated by magnetic field values. In return, it has the potential to be rendered in various semi-active devices such as actuators, soft sensors, robotics, and sound absorption materials. However, different fabrication processes of MA foam would result in different properties and responsiveness, depending on the localized magnetic particles within the foam matrix. Therefore, MA foams were fabricated via three approaches namely in situ, ex situ and hybrid which combined the methods of in situ and ex situ MA foams. The samples underwent strain sweep test, for 1–10% applied strains at off-state and on-state conditions. The results reveal that the hybrid MA foam exhibited the highest storage modulus, about 140 kPa in the absence of magnetic field and the value increased by 95% with the presence of magnetic field. The ex situ MA foam also experienced 95% increment from the off-state to on-state condition, due to improved mobility of the CIPs in the pores of ex situ and hybrid MA foams. Meanwhile, the increment by the in situ MA foam was about 67% only, due to restricted mobility of the CIPs that have been locked in the struts of MA foam. Nevertheless, in situ MA foam may provide consistent behaviour attributed to the lock of CIPs in the struts of PU foam.