Controlling Moisture Content of Natural Fibres in RTM-Process

Abstract

The quality of composite materials based on natural fibres is highly influence by humidity content of the fibres. For a high product quality in the resin-transfer-moulding (RTM) process a constant humidity content has to be achieved. As the humidity content of the fibres can change relative quickly depending on the humidity, measuring humidity content in the mould is beneficial. Near-Infrared-Spectroscopy (NIR) is a widely used tool for humidity content measurement allowing determination of the moisture content within seconds. To do so a calibration model with good accuracy is required. To generate the calibration model a dry flax woven fabric is placed in a climate chamber and weight change is recorded as well as NIR-Spectra. By correlating the spectra with the weight increase a model can be developed allowing to assign the spectra with unknown weight. This allows not only monitoring the moisture content of natural fibres with in the mould. Also can the moisture content reduced to an aspired value by applying vacuum to the preheated mould, before starting the resin infusion.

Usage of Near-Infrared Spectroscopy for Inline Monitoring the Degree of Curing in RTM Processes

“…Beside natural fibers as reinforcement, resin systems with an extremely high bio-based carbon content are especially under development [ 24 ]. The present study expands previous work determining moisture content of flax fiber in the RTM process [ 21 ], using the same NIR micro-spectrometer. As there are no relevant epoxy peaks (1379 nm and 2353 nm) [ 25 ] in the measuring range of the spectrometer, the question arises of whether the available changes in the spectra are useful to determine the degree of curing.…”

“…For other processes in the field of composites, NIR has just been examined to determine the moisture content of a flax fiber textile inline in the RTM process. Here, a good correlation between the H 2 O-Peak at 1924 nm and the moisture content was found [ 21 ].…”

Evaluation of a Micro-Electro Mechanical Systems Spectral Sensor for Soil Properties Estimation

“…Over the recent years, MEMS have been inaugurated to the spectroscopy field through the release of numerous miniaturized spectral radiometers, covering various domains of the electromagnetic spectrum. These sensors have been utilized in the food industry to determine different allergens in powdered foods [35], for estimating the moisture content of natural fibers [36], for estimating milk ingredients [37], for the determination of rosmarinic acid content of dried and powdered Rosmarini folium [38], and for the detection of microplastics in soil [39]. To that end, the technological evolution of miniaturized NIR sensors that are already being used in different sectors could be evaluated for soil analysis purposes.…”