Characterization and durability evaluation of recycled FRP composites and sandwich specimens.

摘要

In this research, use of recycled thermoplastic polymer composites for manufacturing and evaluation of structural products is investigated. Durability (aging) evaluations of those polymers have been carried out to predict their service life. Durability studies were initiated coupon levels to evaluate material performance of recycled ABS polymer at under salt and alkaline aging. ABS polymers were reinforced with 4%, 7% and 12% fiber volume fractions of bi-directional glass fabric (fabric density: 12 oz/yd2). Alkaline solution was prepared by mixing 1.4% of potassium hydroxide (KOH), 1% of sodium hydroxide (NaOH) and 0.2% of calcium hydroxide (Ca(OH)2) salts by weight, which resulted in a pH of 13.0. Salt solution was prepared by adding 3% sodium chloride (NaCl) by weight to the standard water which measured a pH of 7.0. Temperature and humidity were controlled by choosing different freeze-thaw cycles programmed in an environmental chamber for specific humidity and temperature. In this research, the coupon specimens with and without glass fiber reinforced polymers (GFRP) conforming to ASTM standards were conditioned in salt and alkaline solution at room temperature and under freeze-thaw variations (in environmental chamber), before testing them at regular intervals of 1, 4, 8 and 12 months.The maximum tensile strength reductions were 20%, 33.15%, 61.46%, and 75.07% for 0, 1, 3 and 5 GFRP layered coupon specimens, respectively (with a corresponding fiber volume fraction of 0%, 4%, 7% and 12%). The maximum bending strength reductions were 13.31%, 13.78%, 31.33%, and 52.23% for 0, 1, 3 and 5 layer coupon samples, respectively. The maximum strength reductions in compression test were 11.82%, 30%, 29.44%, and 45.75% for 0, 1, 3 and 5 layer coupon specimens, respectively. The impact strength reductions were 17%, 70.87%, 83.42%, and 93.29% for corresponding 0, 1, 3 and 5 layer coupon specimens. Images were taken for both control and aged samples through Scanning Electron Microscope (SEM) to note the FRP surface texture, variation in fabric pattern, fabric matrix interface, and potential delamination due to salt and alkaline aging.Thermoplastic (TP)-thermoset (TS) sandwich composites were manufactured to evaluate their behavior and feasibility for structural applications. The mechanical properties of composite products can be optimized by combining thermosets and thermoplastics to minimize the costs. Six different combinations of TS/TP sandwich specimens were manufactured with and without surface roughening. TS/TP/TS roughened specimen (16% FVF) showed a maximum tensile strength of 11.4 ksi, among six types of sandwich specimens. Similarly, maximum tensile modulus of 0.723 x 106 psi was noted.Research results indicate the significant potential of recycled polymer composites for different applications with the use of continuous glass fabrics (e.g., bidirectional fabrics). Durability evaluations including SEM results indicate that the strength reductions depend on fiber volume fraction and exposed fabric at the cut edges of coupon specimens. The thermoplastic FRP composite must be designed and manufactured such that fabrics are well protected from direct environmental exposure, and proper fiber wet-out is achieved during manufacturing.