Thermal Aging Effects On The Low Velocity Impact Behaviors Of 3d Orthogonal Woven Composites

Three-dimensional orthogonal woven fabric(3DOWF) is made up of warp and weft yarns which are parallel arranged in plane, Z-yarn binding the warp and the weft yarns through thickness direction to keep the stable architecture. This structure feature imparts the high stiffness and high strength to the 3DOWF reinforced composites. Three-dimensional orthogonal woven composites(3DOWCs) can be used as the main bearing parts in engineering structure, and have already been widely used in aircrafts, vehicles and energy field. But the 3DOWCs are often exposed to different temperatures during the manufacture, storage and application, which lead to the thermal aging.Meanwhile, the 3DOWCs are also undergoing impact loading. It is important to understand the impact responses of the 3DOWCs after exposed to high temperatures for different time for the design and safety use of the engineering structures.In this paper, vacuum assisted resin transfer molding technique(VARTM) was used to manufacture three-dimensional orthogonal basalt/epoxy woven composites. The thermal aging effects on the surface morphology and the low velocity impact behaviors of the 3DOWCs after exposed to the 180℃ for different aging hours in air at atmospheric pressure were studied.Scanning electron microscope(SEM) was used to observe the cross-section characteristics of composites after exposured to 180℃ for different hours, combing with Infrared spectroscopy(IR) analysis of cured epoxy-resin to explore the changes of composites. The main conclusions are as follows:(1) The surface morphology and the mass of the 3D orthogonal basalt/epoxy woven composites after exposed to the 180℃ for different aging hours had significant changes. With the aging time increasing, the surface weren’t smooth and the basalt fibers appeared in the composite surface. The color of the composite changed from the black color to light yellow and finally dark yellow, the Infrared spectroscopy(IR) test results showed the chemical change in cured epoxy-resin after exposure to 180℃ for 32 days. The mass of the composites decreased all the time.The mass reduction was more quickly at the initial stage while it tended to be slowly at the later stage.(2) The SEM observations demonstrated that the cracks between fiber and epoxy resin become visible gradually with aging time increasing. The amount and the size of the de-bonding area increased during thermal aging development.(3) Within the certain impact energy, the peak load of the 3D orthogonal basalt/epoxy woven composites and the slope of load-displacement curves monotonically decreased with the increase of exposure time to 180℃, while the displacement and energy absorption increased. And the damage morphology of the composites went unobvious when the composites were impacted at low impact energy.(4) Within certain aging time, the peak load and the displacement of the 3D orthogonal basalt/epoxy woven composites and the slope of load-displacement curves monotonically increased with the increase of impact energy, while the energy absorption decreased. The damage of the 3D orthogonal basalt/epoxy woven composites became serious and the failure mechanisms changed at the same time. The main failure mechanism was resin cracks at low impact energy,while changed to resin cracks and fiber/resin de-bonding with fiber breakage at high impact energy.