Aging of bolted joints prepared from electron‐beam‐cured multiwalled carbon nanotube‐based nanocomposites with variable torques

Abstract

We evaluate the behavior of a bolted joint prepared from electron beam (EB)-cured carbon/epoxy nanocomposites under accelerated weathering environment at varying bolt tightening torques. For strength improvement, different weight percentages (wt%) of multiwalled carbon nanotubes (MWCNTs) in the range 0.1-0.5 wt% were incorporated into the composite laminates; 0.3 wt % of MWCNT had the maximum tensile strength. The properties of EB-cured composites were compared with those of thermally cured ones. For accelerated weathering, cyclic exposure of ultraviolet (UV) radiation as well as condensation at elevated temperatures was conducted for 1000 h on the nanocomposite specimens. The chemical, physical, thermal, and mechanical properties of the nanocomposites were studied under accelerated aging conditions. To determine the failure loads in the bolted joints, specimens were prepared as per ASTM D5961. It was found that after 1000 h of aging, there was only 5% reduction in the ultimate failure load for joints prepared with the addition of MWCNTs. It was also found that the bolt torque had a positive effect on the performance of the joints. The experimental results were validated with progressive damage analysis using the characteristic curve method along with the Hashin damage criteria.

Metal inserts for performance improvement in glass fiber‐reinforced polymer nanocomposite joints under accelerated aging conditions

“…[3][4][5][6] Moisture absorption is noticed as a primary source of FRP composite degradation, which results in the hydrolysis of resin, microcracking, epoxy swelling, and debonding of the fiber/ matrix interface. [7][8][9][10] UV radiations and elevated temperature act as a secondary source, which are responsible for the physical and chemical changes in the constituent resin because of the series of complex processes characterizing UV radiation and oxygen. [11,12] At elevated temperatures, the degradation starts when the resin material reaches the glass transition temperature (T g ).…”