The effect of surface treatments on the mechanical properties of basalt reinforced epoxy composites

Abstract

Basalt fiber is an emerging alternative reinforcement to glass or carbon depending upon the application. An important contributing parameter to ultimate performance of any composite is the fiber–-matrix interface, to which toughness and compressive strength are intimately related. To better understand this matrix fiber interaction in controlling properties, we compared different modification strategies and the impact upon the properties of composites. Strategies focussing upon mechanical interlocking through increased surface roughness and covalent chemical bonding using sol/get methods were explored. Combined methods were also used to explore synergistic behavior as well as the use of aliphatic triethylenetetramine (TETA) to react with any covalently attached epoxy groups. Results from single ply composites showed that when the properties were fiber or fiber/matrix dominated, the sol/gel or epoxy silane method gave the largest improvement in ultimate tensile strength increasing 66% and 27% for uni-weave 0° and 45° laminas. The combined surface modification methods exhibited increases of 45% and 13% for the same laminas. When properties were matrix dominated, the combined strategies produced the highest improvements in ultimate tensile strength of about 55% compared with 37% for sol/gel modification. For 16-ply plain weave laminates, epoxy silane surface treatments produced the greatest improvements in compressive and interlaminar shear strengths, increasing 52% and 21%, respectively. This correlated with fiber- and fiber/matrix-dominated results from single ply laminas. The combined treatment using TETA however decreased shear and compressive strength by about 20%, while scanning electron microscopy (SEM) evaluation and dynamic mechanical thermal analysis (DMTA) attributed this to increased resin ductility and plasticization