Effect Of Fillers And Low Profile Additives On TheBending Of Pultruded Composites

This paper deals with the effect of fillers and additives on the mechanical properties of pultruded composites. Six materials with varying filler and low profile additive (LPA) content have been manufactured by pultrusion using E-glass fiber reinforcement roving in a general purpose unsaturated polyester resin. The materials were pultruded in the form of a 50x6.4 mm rectangular cross-section profile. The mechanical tests consist of three-point-bending tests according to the ASTM D2344 Standard for short beam shear tests and the ASTM D739 Standard for flexural tests. Additional tests were performed at other span-to-depth (L/h) ratios varying from 5 to 24. The test results are analysed to serve two different objectives. The first objective consists in determining the effect of fillers and LPA content on the mechanical behaviour. Within this respect, it was found that an increase in the filler content form 20 to 40% results in a small decrease in the shear strength while the flexural strength seems insensitive. The addition of LPA from 5 to 20% reduces the shear strength without affecting the flexural strength. The second objective consists in determining the possible misinterpretation of three-point-bending standard tests. The results of this investigation show that, for some of the materials investigated, a clear shear fracture was obtained with an L/h ratio of 11 instead of L/h=5 as recommended by the ASTMD 2344 standard. Actually, for small L/h ratios, the fracture is preceded by a plastic flow of the specimen side under compression. This behaviour is more pronounced for the materials containing LPA.