Influence of resin additives on failure behaviour of pultruded glass/polyester composites shapes

Abstract

Pultrusion is one of the t;astest and most costetTectivc processes by which composites can be mam~t'actured. Lately, the uses of pultruded composites have proliferated to include a number of new structural applications [1, 2]. These composite structures have desirable properties in corrosive and chemical environments. For all these reasons, pultruded composite structures are becoming more and more competitive with steel and concrete for construction. With the increasing possibilities of using pultruded composites in the construction industry, the need for full characterization [3, 4] of these materials becomes essential. Some studies [5-7] have dealt with the effect of different processing parameters on the mechanical and thermal properties of pultruded profiles. A recent study [8] has examined the mass and volume fraction properties of pultruded glass/polyester and glass/vinylester composites. The authors concluded that a wide variation of these parameters exist in specimens cut from similar samples of pultruded materials. In the same study, an attempt to identify the filler types and to separate the fillers from the reinforcement was successfully carried out. As mentioned before, it is of vital importance to quantify the effect of resin additive on the mechanical properties of pultruded profiles. In general, fillers are used with resins (here, unsaturated polyester) to help reduce cost. They are much more expensive than the resin itself as well as the most reinforcing agents. However, there are other advantages associated with the use of fillers. Their use permits higher curin~ temperatures by reducing the concentration of" reactive materials, which, in turn. tends to reduce the peak exotherm temperature. Clays and carbonates arc th,~ most commonly used fillers. Furthermore, other types of additives can be used such as dyes and pigments, flame-retardant substances (antimony trioxide) and ultraviolet absorbers. In order to produce a good final profile, all these substances must be compatible with the resins. the catalyst and the accelerators used. In thi~ work. ll~e considered profile shape is a UPN (channel) geometry of O0 :x 35 × 8 >,~ 8 ram. The localization ol II~e different reintbrcements in the cross section is shown in Fig. i. The glass fibre reinforcement is constituted by a contilmous strand mat (fibre randomly odemed) and by unidirectional fibre called direci co\ms. The matrix set is conslituted with a mixture of two different kinds o1" p,dycster tmsaturated isophtalic