Effect of Hydraulic Liquid and Sea Water on the Mechanical Characteristics of Polymeric Fibrous Structures

Abstract

The degradation of the mechanical characteristics of typical composite materials under the action of the working liquid is studied. Polypropylene and epoxy specimens reinforced with a glass fabric with the warp fiber orientation 0, ± 45, and 90° have been investigated according to the ISO 527-4 standard. The materials were a polypropylene composite based on stitched glass fabric and an epoxy-bonded glass fabric and carbon fabric reinforced composite. The basic mechanical characteristics of the materials under investigation have been determined. The specimens were kept in an AMg10 hydraulic liquid and in sea water for 910 hours with periodic weighing. The characteristics of the process of adsorption of working liquids by the materials under investigation: adsorption rate coefficient and the maximum amount of the adsorbed liquid have been determined. An investigation to detect damages caused by the liquids adsorbed by materials has been carried out. The specimens with adsorbed liquids were held at 255–373 K with subsequent tensile test. It has been found that the liquid in the material causes its swelling owing to liquid pressure. It is assumed that the characteristics degrade in proportion to swelling pressure. The effect of the above liquids on the strength characteristics of the materials under investigation has been studied by keeping them in these liquids for different time intervals (0–840 h), followed by a tensile test. The effect of through-thickness stitching along the test direction 90° on the mechanical characteristics of a material with a liquid in comparison with other test directions has been studied. The laws governing the effect of the above liquids on the mechanical characteristics of materials in time have been established. Based on experimental data, a model of the behavior of the composite under investigation under the above conditions has been developed, and numerical calculations have been performed. The calculated curves give a fairly good fit to experimental data, which confirms the described approach to be correct.