Measurement of out-of-plane permeability and textile compressibility: results of the 2nd international benchmarking exercise and road to standardisation
Topic(s) : Experimental techniques
Co-authors :
Ana X.H. YONG (UNITED KINGDOM)Abstract :
Introduction
The successful manufacture of composite materials by liquid composite moulding (LCM) processes is underpinned by effective process design, for which characterisation of the textile reinforcement materials is of particular importance. This includes measurement of the permeability, typically measured as the in-plane and out-of-plane permeability separately, and the compressibility of the textile reinforcement material. Following several international benchmarking exercises, a method for measurement of the in-plane permeability was successfully standardised in 2023 [1-4]. Following these activities, the first international benchmarking exercises for measurement of the out-of-plane permeability and textile compressibility were completed in 2021 [5,6]. These led to a series of recommendations for refined test procedures to be used in a second round of benchmarking for each exercise. The aims of repeating the activity with these refined test procedures were to develop suitably accurate and reproducible test procedures for standardisation. This work presents the outcomes of the two latest international benchmarking exercises and the status in the road to standardisation.
Materials and methods
For both benchmarking exercises, participants were supplied with 2/2 twill woven glass fabric, supplied by Saertex. The test fluid used was Dow Corning Xiameter PMX 200 100 cst.
In the out-of-plane permeability measurement exercise, 19 participants were instructed to measure the permeability using a saturated or unsaturated 1D test method. Five measurements were to be taken at each of the three prescribed volume fractions: 45%, 50% and 54%. It was a requirement to seal the edges of the specimen using either a sealant, o-ring or clamping of the specimen in order to minimise the effects of race tracking.
In the compressibility measurement exercise, 21 participants were instructed to measure the peak pressure at a defined specimen thickness, using a direct thickness measurement method such as LVDTs. Five repeat tests were carried out on both wet and dry specimens and each specimen stack was to be comprised of the same number of layers of fabric to ensure an identical volume fraction for each participant.
Results
An overview of the results can be seen in Figures 1 and 2 for the permeability and compressibility benchmarking exercises, respectively. A statistical analysis of the results, analysis of any causes of variation, and the current status in the standardisation of the test procedures will be presented in this work.
The successful manufacture of composite materials by liquid composite moulding (LCM) processes is underpinned by effective process design, for which characterisation of the textile reinforcement materials is of particular importance. This includes measurement of the permeability, typically measured as the in-plane and out-of-plane permeability separately, and the compressibility of the textile reinforcement material. Following several international benchmarking exercises, a method for measurement of the in-plane permeability was successfully standardised in 2023 [1-4]. Following these activities, the first international benchmarking exercises for measurement of the out-of-plane permeability and textile compressibility were completed in 2021 [5,6]. These led to a series of recommendations for refined test procedures to be used in a second round of benchmarking for each exercise. The aims of repeating the activity with these refined test procedures were to develop suitably accurate and reproducible test procedures for standardisation. This work presents the outcomes of the two latest international benchmarking exercises and the status in the road to standardisation.
Materials and methods
For both benchmarking exercises, participants were supplied with 2/2 twill woven glass fabric, supplied by Saertex. The test fluid used was Dow Corning Xiameter PMX 200 100 cst.
In the out-of-plane permeability measurement exercise, 19 participants were instructed to measure the permeability using a saturated or unsaturated 1D test method. Five measurements were to be taken at each of the three prescribed volume fractions: 45%, 50% and 54%. It was a requirement to seal the edges of the specimen using either a sealant, o-ring or clamping of the specimen in order to minimise the effects of race tracking.
In the compressibility measurement exercise, 21 participants were instructed to measure the peak pressure at a defined specimen thickness, using a direct thickness measurement method such as LVDTs. Five repeat tests were carried out on both wet and dry specimens and each specimen stack was to be comprised of the same number of layers of fabric to ensure an identical volume fraction for each participant.
Results
An overview of the results can be seen in Figures 1 and 2 for the permeability and compressibility benchmarking exercises, respectively. A statistical analysis of the results, analysis of any causes of variation, and the current status in the standardisation of the test procedures will be presented in this work.