Bulk Energy Transferability Linked to Critical N–H Modes of an Interfacial Nanoscale Surface Modification via Unique Isophorone Diisocyanate Amine Exchange Reaction

A surface‐modified carbon‐fiber reinforced epoxy (CF/E) via a unique isophorone diisocyanate amine (IDA) reaction produces a new interfacial epoxy‐polyurea “matrix” (IEPM) that elicits excellent mechanical energy transferability in brittle CF/E. The chemical bonding property in the IEPM molecule is produced via moieties of an epoxy mixture and N‐H‐concentrated urea molecules, where IDA thermodynamics are controlled via a curing parameter, t c (in hours). Nano‐scale properties of the IDA reaction, confirmed via fourier‐transform infrared spectroscopy and chemical mapping of molecules comprising the IEPM structure, are linked to bulk mechanical energy transferability, specifically loss modulus, E ″(ω), and post‐elastic energy absorption. Using dynamic mechanical analysis (DMA) of six test specimens and a Generalized Maxwell Model – verified via Prony Series calibration of the storage modulus to DMA data to compute relaxation parameters – the ultrathin IEPM is isolated, and E ″(ω) is computed as a function of t c . IEPM that is produced via t c  = 0 exhibited two, six, and ten times greater loss modulus than IEPM produced via 0.5 ≤ t c  ≤ 2; t c  = 3.5; and t c  = 24 (baseline design utilizes cured CF/E). Finally, IDA surface‐modification of CF/E improved energy absorption capacity (post‐elasticity) between 250% ( t c  = 0.5) and 300% ( t c  = 0).