Elastic modulus measurement of thermoplastic composites through modal analysis

Abstract

Conventional tensile testing of materials employ pulling of a specimen till it breaks to determine the elastic modulus and other tensile properties. Modal analysis is one of the ways to measure the elastic modulus without destructing the sample. The present study was carried out to evaluate the elastic modulus of short carbon fiber (SCF) reinforced polyethersulfone (PES) composites filled with potassium titanate whisker (PTW) and ultra high molecular weight polyethylene (UHMWPE) through modal analysis. Specimens were prepared by extrusion and injection moulding processes. Modal analysis was done with cantilever type free-vibration test rig on the developed composites using an accelerometer sensor. Based on the acceleration response of the composites, their natural frequencies and damping values were determined. Further, elastic moduli of the composites were computed and compared with that of actual tensile test. Elastic modulus of PES/SCF composites determined by free vibration test was well in agreement with that of tensile test results. In addition, numerical modal analysis simulation was performed for by considering the tensile modulus and density of each of the composite material. Natural undamped frequencies of the composites found by numerical modal analysis were closer to that of the experimental values.