Control of laminate quality for parts manufactured using the resin infusion process

Abstract

Resin infusion is a manufacturing process used to produce fibre-reinforced thermo-set polymer components. This process is utilised in a range of industries such as aerospace, automotive, marine, rail and defense and is a cheaper method when compared to other closed mould or autoclave manufacturing methods, particularly as the size of the parts increases. In this study, wet compaction characteristics and behaviour of three glass fibre reinforcements were analysed, and 2D panels were manufactured with a selection of inlet and vent pressure combinations during both the filling and post-filling stages of the process to achieve control of the final fibre volume fractions. Reinforcement thickness and resin pressure were monitored throughout each experiment and the achieved fibre volume fractions were measured post-manufacture. Void content was analysed microscopically and related to the respective experimental parameters set. The compaction result fairly predicted the achieved fibre volume fraction of the manufactured part. The possibility of controlling the fibre volume fraction through control of the post-filling pressure was demonstrated. Even though there was a risk of increased void content with some post-filling configurations, the fibre volume fraction could still be controlled without creating voids with careful application of post-filling conditions.

Experimental and Numerical Study of Vacuum Resin Infusion for Thin Walled Composite Parts

“…In such cases, the simulation continues until the blocking of the vacuum vent by the resin flow. An indicator of this blockage is a condition (30) at the boundary Γout surrounding the vacuum port. In order to identify time instant when a first dry spot arises and its localization the use of change in averaged pressure in the non filled zones of the prepreg has been proposed.…”

“…Due to the above mentioned improvements in vacuum infusion processes, they were successfully implemented in the manufacture of aircraft structures (usually, shell type) [1][2][3], blades of wind turbines [1,9,10,27], ship's hulls [1,4,6,27,29], large-sized parts of cars bodies [30], details of spacecraft etc. [1,29].…”

“…In the dry region, where the low air pressure vac p is supplied due to connection to the vacuum vent, the compressive pressure exerting a compression effect on the preform is equal to [14]. This phenomenon, which significantly changes the permeability of the preform for the moving liquid resin, as well as the fact that the pressure of the infusible resin during the vacuum process is much lower than with the traditional RTM, when the vacuum is deficient before the start of preform's filling [10], can contribute to the creation of incompletely saturated zones and dry spots [4,5,19,[29][30][31]. The presence of differently oriented layers in laminated preform leads to the appearance of undesirable phenomena: the impregnation of the layers depends on their permeability in the direction of the resin front propagation, as well as leads to the layers deformation that disrupt their packing [13,23].…”

Experimental and Numerical Study of Vacuum Resin Infusion for Thin-Walled Composite Parts

“…Due to the above-mentioned improvements while ensuring a low degree of the resin cure at the end of the preform filling [13,[15][16][17][18][19][20][21] they were successfully implemented in the manufacture of aircraft structures (usually shell type) [1,22,23], blades of the wind turbines [1,20,[24][25][26][27], ship's hulls [1,2,20,24,25], details of spacecraft [1,28], large-sized parts of cars bodies [29,30] and in the defense industry [7,27].…”

“…In the dry region, where the low air pressure p vac is supplied due to connection to the vacuum vent, the compressive pressure exerting a compression effect on the preform is equal to p void comp = p atm − p vac , whereas in the region filled with liquid resin, the pressure approaching the atmospheric pressure counteracts the external, atmospheric pressure p f ill comp = p atm − p res [6]. This phenomenon, which significantly changes the permeability of the preform for the moving liquid resin, can contribute to the creation of incompletely saturated zones and dry spots [7,12,24,28,30,31]. Another reason for the preform compaction is a wetting compaction, which can arise due to the lubricant effect of the resin when it wets the fibers [32].…”