In this paper the authors discuss the effects of particles (fillers) mixed in a composite polymer on the space charge measurement techniques. The origin of particle-induced spurious signals is determined and silica filled epoxy resin is analysed by using the laser-induced-pressure-pulse (LIPP), the pulsed-electroacoustic (PEA) and the laser-induced-thermal-pulse (LITP) methods. A spurious signal identified as the consequence of a piezoelectric effect of some silica particles is visible for all the methods. Moreover, space charges are clearly detected at the epoxy/silica interface after a 10-kV/mm poling at room temperature for 2 hours. Physical backgroundThe presence of particles in the material can alter space charge measurements in two ways: firstly by perturbing the diffusion of heat or the propagation of pressure waves, and secondly by adding spurious signals. These different alterations are studied in the following subsections. Heat diffusion and elastic wave propagationThe thermal methods rely on thermal diffusion to perform space charge measurements, and the pressurewave-propagation and the electro-acoustic methods rely on wave propagation. Any perturbation to the diffusion of heat or to the propagation of pressure waves may therefore alter these measurement methods.