Ricerc@Sapienza

Hybrid composite samples with different carbon and glass fiber layers arrangement were produced by resin transfer molding (RTM) in an attempt to disclose the effects of low temperature on their flexural and low velocity impact behavior. Flexural tests were carried out at T = −50°C and the failure modes were examined, while impact tests, always at T = −50°C, were performed at penetration and at indentation in the range from 10 J to 30 J. The damage extension was accurately evaluated by ultrasonic non-destructive testing.

In this chapter we review the impact behavior of composite structures consisting of long-fiber reinforcement and thermosetting matrices based on epoxy resins loaded with carbon nanoparticles. Different types of nanotubes (single-, multi-walled, coiled) and graphene nanoplatelets are considered as carbon reinforcement of the polymer matrix.

The effects of the integration of continuous sheets of randomly oriented multi-walled carbon nanotubes on the low velocity impact behavior of cross-ply carbon/epoxy laminates have been investigated. Three different energy levels were used, namely 5 J, 10 J, and 20 J and significant reductions in delaminated area in the range 11%–39% compared to the baseline laminates were achieved by incorporating interleaves at each 0/90 interface. This resulted in a better flexural damage tolerance of modified laminates.

The unremitting quest of natural and renewable materials able to replace their synthetic counterparts in high-performance applications has involved also sandwich structures. In this regard, the aim of this work is to characterize the impact response, in both high- and low-velocity conditions, of green sandwich structures made of agglomerated cork as core and flax/epoxy laminates as face sheets. Both bare cork, flax skins, and complete sandwich structures were subjected to impacts at three different energy levels representing the 25%, 50%, and 75% of the respective perforation thresholds.

Natural fiber composites have the potential to be widely applied as an alternative to or in combination with glass fiber composites in sustainable energy-absorbing structures. This study investigates the behavior of hemp fiber-reinforced vinylester composites when subjected to low-velocity impact loading by using an instrumented falling weight impact equipment. Different stacking sequences are tested, including a hybrid pattern resulting from a combination of natural and traditional glass fibers. Both penetration and indentation tests are performed.