Impact of micro-cracking and self-healing on electromagnetic interference shielding of ultra-lightweight engineered cementitious composites

Abstract

The explosion of wireless devices and electronic equipment has escalated electromagnetic pollution, sparking health concerns and demand for building shielding materials. Ultra-lightweight engineered cementitious composites (ULW-ECCs) incorporating carbon fibres (CF) and calcined petroleum coke (CPC) were proposed for electromagnetic interference (EMI) shielding. The effects of microcracking and self-healing, common in real-world applications, on EMI shielding effectiveness (SE) were examined. Two levels of microcracking (low and high) were induced, each followed by a self-healing process in a natural environment. Various lengths and contents of CFs, along with different CPC contents, were tested. Damage evolution throughout the cracking–self-healing cycle was monitored by measuring resonant frequency, while microstructural variations were observed via optical microscopy and SEM-EDS. Results show hybrid CF with polyethylene fibre enhanced cracking resistance but reduced strain-hardening capacity. CF was proved more effective than CPC in enhancing both EMI SE and cracking resistance. EMI SE was influenced by the length and content of conductive filler. Microcracking reduced EMI SE by up to 24.8% at 1.0GHz, depending on severity and conductive fillers. Higher conductivity based on contact conductive pathways enhanced EMI SE but led to greater SE loss after cracking. Self-healing restored EMI SE to its original levels after low-degree cracking and recovered SE to low-cracking levels even after severe damage. The multiple microcracking of ULW-ECCs promotes the nucleation of healing products and crack closure. These findings provide insights into EMI shielding of ULW-ECCs under microcracking and self-healing, highlighting practical applications.