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The crashworthiness characteristics of rectangular tubes made from a carbon-fiber reinforced hybrid-polymeric matrix (CHMC) composite were investigated using quasistatic and impact crush tests. The hybrid matrix formulation of the CHMC was created by combining an epoxy-based thermosetting polymer with a lightly crosslinked polyurea elastomer at various cure-time intervals and volumetric ratios. The load-displacement responses of both CHMC and carbon-fiber reinforced epoxy (CF/epoxy) specimens were obtained under various crushing speeds; and crashworthiness parameters, such as the average crushing force and specific energy absorption (SEA), were calculated using subsequent load-displacement relationships. The CHMC maintained a high level of structural integrity and post-crush performance, relative to traditional CF/epoxy. The influence of the curing time and volumetric ratios of the polyurea/ epoxy dual-hybridized matrix system on the crashworthiness parameters was also investigated. The results reveal that the load carrying capacity and total energy absorption tend to increase with greater polyurea thickness and lower elapsed reaction curing time of the epoxy although this is typically a function of the loading rate. Finally, the mechanism by which the CHMC provides increased damage tolerance was also investigated using scanning electron microscopy (SEM).

A synthesizable interfacial epoxy−polyureahybridized matrix (IEPM), composed of chemical bonded nanostructures across an interface width ranging between 2 and 50 μm, is a candidate for dialing-in molecular vibrational properties and providing high-impact dynamics resistance to conventional fiber(x)-reinforced epoxy (F/E), engendering an x-hybrid polymeric matrix composite system (x-IEPM-t c ). Atomic force microscopy and scanning electron microscopy elucidate the interfacial nanoscale morphology and chemical structure via reaction kinetics of curing epoxy (as a function of time, t c ) and fast-reacting (prepolymerized) polyurea. Nanoinfrared spectroscopy (nano-IR) spectra, per non-negative matrix factorization analysis, reveal that simultaneous presence of characteristic epoxy and polyurea vibrational modes, within a nanoscale region, along with unique IEPM characteristics and properties following thermomechanical analysis and dynamic mechanical analysis (DMA), indicate chemical bonding, enabling IEPM reaction kinetics, as a function of t c , to control natural bond vibrations and type/distribution of interfacial chemical bonds and physical mixtures, likely due to the bond mechanism between −NCO in polyurea and epoxide and −NH 2 in epoxy hardener (corresponding to characteristic absorption peaks in nano-IR results), leading to enhanced IEPM quality (fewer defects/voids). Test results of ballistic-resistant panels, integrated with thin intermediate layers of x-IEPM-b-t c , confirm that lower t c significantly enhances loss modulus (∝ material damping and per DMA) in impact dynamics environments.

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