Applying acoustic emission to investigate failure mechanisms on bending of polymer-based composite sandwich panels

In recent years, due to achieving desired properties, increasing application of Composite in various industries is observable. Exact determination and evaluation of failure mechanisms lead to modified designs and helps assessment of loading in composite structures, specially sandwich panels. In this paper, failure mechanisms during bending of Foam / Glass - Polyester Sandwich panels, which degraded by pre-impact of various energy, have been investigated by acoustic data analysis. 4 different Lay-up techniques for laminates with 4 types of with and without pre-impacts and totally 16 samples were studied. Matrix crack, fiber de-bonding, fiber breakage and foam crack were the mechanisms were investigated through sample failure photos, acoustic frequency count analysis, extracted energy in each frequency range and force-time diagrams. Results showed that brittle failure mechanisms containing matrix crack and foam crack release more condensed and in lower frequency range with higher energy acoustic counts in comparison with ductile failure mechanisms like as fiber de-bonding and fiber breakage. Ductile failure mechanisms release more scattered in higher frequency range but with lower energy acoustic counts. Acoustic Results which applied to assess failure mechanisms validated by visual pictures and force diagrams also lead to a new frequency range determination for foam crack (190 to 220 kHz).