Use of a simple, inexpensive pressure sensor to measure hydrostatic resin pressure during processing of composite laminates

Abstract

A simple and cheap method of measuring the resin pressure within a composite laminate during processing is presented. The method consists of using a small diameter, long needle filled with inert fluid and connected to an external pressure sensor, to measure the resin pressure at a point inside a composite laminate. This method can be used to investigate resin flow, laminate compaction, the control of voids, and in several composite material processing methods such as autoclave processing, hot press curing and resin transfer molding. The sensors are suitable for research and development or troubleshooting, but not for production. Sensor assemblies were developed and tested to show that their response is reproducible, linear and stable with temperature and time. Resin pressure profiles for two AS4/3501‐6 laminates were generated and compared. The experimental results were also compared to the resin flow simulation of a general processing model for composites, COMPRO. It is shown that the resin profile in the laminate is influenced by the presence of the bleeder cloth and the vacuum bag pressure. A significant pressure drop corresponded to the point of minimum viscosity of the resin. Finally, the resin pressure was stabilized when the resin reached gelation.

Numerical and Experimental Study of the Bleeder Flow in Autoclave Process

“…Resin flow is the primary mechanism for removing the excess resin and voids entrapped inside the laminate and obtaining the desired fiber volume fraction and laminate thickness [1][2][3]. Mathematical models of resin flow in composite laminates have been developed with various approaches ranging from lubrication theory to soil mechanics, with different simplifications and assumptions related to resin flow, the shape and packing of the fibers [4].…”

Resin infusion/liquid composite moulding (LCM) of advanced fibre-reinforced polymer (FRP)

“…A large amount of work has been presented on monitoring of the RTM process cycle [19,38,[81][82][83][84][85][86][87][88][89][90]. While visualisation of the flow front progression through a transparent top mould can help understand the effect of race-tracking [38,81,91] and other localised effects such as inserts or converging fronts, the use of such moulds has been limited to laboratory work and they are not suitable for industrial applications.…”

“…Dielectric sensors, as well as monitoring flow front progression, can be used to monitor the degree of cure of the resin [85,90,94]. Pressure transducers can be used, and will also provide useful data of the fluid pressure in the impregnated area of the preform [86]. Thermocouples have also been used, but while cost-effective and durable, the high thermal diffusivity of metal moulds can result in a lag in the response of the sensor [95].…”

Resin pressure and resin flow inside tapered laminates during zero-bleeding and bleeding processes

“…The results from the laminates processed under bleeding condition prove that resin pressure gradients exist in through-thickness direction and resin flows from bottom to top, and finally to the bleeder materials [3,4,5]. [3][4][5] In other words, only 1D resin flow occurs. As a result, the fiber volume fraction at top region is generally higher than that at bottom region.…”