Tool interface pressure during the forming of model composite corners

Tracking consolidation of out-of-autoclave prepreg corners using pressure sensors

“…For external radii corners, the thickness increases immediately outside of the corner region before decreasing in the flange, while the opposite was observed for the internal radii corners, which show a local decrease in thickness before the corner and an increase in thickness in the corner. This is generally accepted as the typical thickness profile in the literature [14,15] and is in line with trends from previous studies [11,12]. The laser arm scanning of the components also allowed for the extraction of the flange region flatness, corner radius, and internal angle, which further qualify the part tolerance and warpage.…”

“…The 10 mm external corner part showed a peak differential pressure of 1.66 times (i.e. the measured pressure is 1.66 times the applied vacuum pressure), agreeing closely with the bagside radius to tool-side radius ratio of 1.72, which analytical equations indicate should be equal to the ratio between tool-side pressure and bagside pressure [12]. The 15 mm external corner showed a peak pressure of 1.52 times the vacuum pressure as compared to the radii ratio of 1.48, the 25 mm corner registered a maximum relative pressure of 1.28 compared to the predicted 1.29, and the 40 mm corner peaking at 1.20 times the vacuum pressure, as compared to the radii ratio of 1.18.…”

“…The ability to observe consolidation pressure has come far, from single-shot films used by Wang et al [11] that only provide a single maximum consolidation pressure, to the pressure mapping sensors that allow continuous time-resolved measurements. A concise overview of different pressure measuring sensors and their capabilities was given in the recent study by Hubert and Kratz [12], who used a relatively thick (1.35 mm) pressure mapping sensors to experimentally confirm the change in reacted pressure of silicone sheet from the bag side to the tool in corner geometries. Where previous studies were limited to single measurements [11] or model material systems at room temperature [12], this study employs thin-film (0.1 mm) pressure mapping sensors in an actual composite lay-up scenario to track toolside pressure during material deposition and the pressure gradient in corners during oven vacuum bag moulding at elevated temperature that is responsible for final part quality, which in this study is quantified using the part thickness.…”

“…This second ratio is considered by the authors as a better metric to compare different geometries as it intrinsically distinguishes between internal (ratio less than 1) and external (ratio greater than 1) geometries which is not achieved when using laminate thickness over tool radius. Furthermore, analytical models for predicting the change in pressure in corners, such as those used by Hubert and Kratz [12], indicate that the ratio of tool side pressure to bag side pressure is equal to the ratio of bag side radius to tool side radius. As such this geometric measure provides a direct analytical prediction of the pressure change in the corner further adding to its value as the measure to characterise corners.…”

Modeling of contact mechanics and defects investigation in automated fiber placement

“…Typically, investigations into the contact condition and laying quality of AFP predominantly employ variable control methods, and the appropriate parameters can be obtained through abundant experimental data. [17][18][19] For example, Bakhshi et al 20 systematically studied the influence of roller parameters on laying pressure and quality. The extensive experimental data offers valuable samples for parameter optimization of fiber placement under comparable circumstances.…”