STRESSES AND DEFORMATIONS INDUCED DURING MANUFACTURING .2. A STUDY OFTHE SPRING-IN PHENOMENON

It has been observed that residual stresses always build up during the fabrication of composite components. Such stresses can change the sha pe of a component when it is removed from the mould. This paper examin es the spring-in induced during fabrication of composite angle compone nts by such residual stresses. The sample composite components were fa bricated from unidirectional carbon/epoxy pre-preg tape and plain-weav e carbon/epoxy pre-preg fabric, as well as from dry carbon fabric and resin using the resin transfer moulding (RTM) technique. The effects o f lay-up, orientations, part thickness, tool angle, tool material, etc . were investigated. The results show that (1) the tool material has a n insignificant effect on the degree of spring-in, (2) spring-in is in sensitive to the lay-up sequence for symmetric lay-ups, (3) spring-in does not depend on ply orientation angles in the case of fabric lamina tes, (4) spring-in remains constant for almost all radius/thickness ra tios and (5) spring-in decreases with an increase in the tool angle. C omparison with the theoretical model developed by Jain and Mai [1] is provided and good agreement is found.