Experimental investigation of strain and damage sensing of polymer bonded energetics with MWCNTs and conductive grains under cyclic compressive loads

Abstract

This experimental investigation is to gain an insight into the strain and damage sensing abilities of polymer bonded energetic material with multiwalled carbon nanotubes (MWCNTs) and conductive grains under cyclic compression test. Self-sensing in a polymer system is achieved by the addition of MWCNTs in the system where networks of MWCNTs provide a piezoresistive behavior when subjected to compressive loading. Polydimethylsiloxane (PDMS) is an elastomer which is a commonly used binder in a polymer bonded energetic materials. Ammonium Perchlorate is the energetic crystal used in the system. Metal particle additives such as aluminum grains are added to the AP-PDMS-MWCNTs system as fuel to the energetic mixture. Exploratory results show that PDMS and AP-PDMS has very little sensing abilities as PDMS is a non-conducting material thus have a large resistance values but the electrical response (in the Megha Ohm range) observed is largely due change in the geometry and noise. Presence of the networks formed by MWCNTs in a AP-PDMS-1\% Wt. MWCNTs sample, there is a baseline resistance value of 114.31 ± 8.71 kΩ which is more useful for sensing purpose. With the addition of aluminum powder, value of baseline resistance is 117.995 ± 11.23 kΩ there is relatively no changes to the baseline resistance. When AP-AL-PDMS-1\% Wt. Compression-Compression cyclic study were performed at three different strain ranges from 3-7\% (no visible damage), 18-23\% (minimal damage occurred) and 36-42\% (damage is clearly visible). MWCNTs material system is tested, there is a permanent change in the electrical parameters due to the damage that occurred in a cyclic compressive loading. These indications show the strain and damage sensing ability in polymer bonded energetic materials with MWCNTs and AL powder as fuel.