EFFECT OF DRILLING PARAMETERS ON THE FINISH AND MECHANICAL-PROPERTIES OF GFRP COMPOSITES

Drilling tests were carried out on glass fibre reinforced plastic composites, in order to verify the effect of machining parameters on the cut quality and on the mechanical behaviour of the material under examination. A novel method was adopted to measure the width of the damage zone. The experimental data showed that the width of the damage zone is correlated to the ratio between drilling speed and feed rate, Vr/Vt; in particular, the higher the Vr/Vt value, the better the cut quality. The damage zone decreases to a minimum value for a definite Vr/Vt, beyond which damage zone constant. The tensile strength of specimens with holes is not influenced by the quality of the material at the edge of the hole, whereas the bearing strength suffers a marked reduction with increasing damage zone width when the latter is large. For small damage zone widths, no correlation seems to exist between the bearing strength and the damaged zone. © 1990.