In this study, the effects of plastic deformation and failure of the folded part on the folding behavior of non-crosslinked ethylene propylene diene terpolymer/paraffin oil/silica gel composites were investigated. The folding behavior was evaluated by the residual fold angle of a folded specimen; a lower fold angle
indicates an enhanced folding performance. The fold angle decreased with increasing oil and silica content and was correlated with the tensile yield strain, which is generally related to plastic deformation. Furthermore, the test speed dependence of the fold angle for each set of oil contents and test temperatures was investigated. The fold angle decreased with a decrease in the test speed and an increase in the test temperature. Scanning electron microscopy revealed that the low-fold angle, which indicates an improvement in the folding behavior, was caused by the destruction (voids, crazes, and cracks) of the folded part.