Abstract
The purpose of this investigation is to study the performance degradation mechanism of CRRP composite materials used in the structure of a solar UAV under acid rain environment and to provide references for the structural design of the solar UAV. An aging test was designed according to the actual working conditions of the solar unmanned aerial vehicle and was carried out by continuously immersing the composite material in both deionized water and an acidic solution with a pH of 2.0 at 60°C. The mechanical behavior of the composites was studied through a three-point bending test. The results showed that after 120 days of aging test, the composite material exhibits different characteristics in the two conditions. The composite material under the hygrothermal conditions finally reached the equilibrium moisture absorption content of 1.07%, and the flexural strength decreased by 8.77%. The composite material under acidic conditions deviated from the Fick behavior in the final stage of the test, and the final moisture content was 2.88%, and the bending strength decreased by 26.43%. Several typical empirical models were analyzed, and a hyperbolic tangent function empirical model with moisture content as the main variable was used to predict the CFRP flexural strength degradation process, and good results were obtained. The effect of aging conditions on the microstructure of composite materials was observed by SEM, and the aging mechanism of composite materials was analyzed. The corrosion of the polymer matrix and the debonding of the fiber/matrix interface are the root causes of the performance degradation of composite materials.
Highlights
Fiber-reinforced polymer (FRP) composites have become the most promising structural materials of present century
The high strength and toughness of fiber-reinforced composite materials are achieved by introducing high-strength fibers into the matrix material to form an interface between the fibers and the matrix
Thermoset resin presented in composite materials, such as epoxy resins, absorbs the moisture in during operations in hydrothermal environments
Summary
Fiber-reinforced polymer (FRP) composites have become the most promising structural materials of present century. Their high specific strength and high specific stiffness have made them find applications in variable engineering fields, including aerospace, transportation, civil facilities, and maritime facilities [1,2,3,4,5]. Thermoset resin presented in composite materials, such as epoxy resins, absorbs the moisture in during operations in hydrothermal environments. The water molecules that entered the composite material during the moisture absorption are usually divided into unbound molecules and bound molecules. Unbound molecules diffuse into the internal pores and cracks of the composite materials, without reacting with the resin matrix; the polymer does not swell and plasticize. The bound molecules combined with the epoxy hydrophilic group destroy the polymer chain and lead to the expansion and plasticization of the epoxy resin [9, 10]
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