Digital volume correlation analysis of thermoplastic carbon fibre sheet moulding compound composites
Topic(s) : Material and Structural Behavior - Simulation & Testing
Co-authors :
Salaheddine MADI (BELGIUM), Yi WANAbstract :
Recently, the mechanical characterisation of carbon fibre-reinforced thermoplastic sheet moulding compounds (CFRTP-SMC) materials has gained a lot of attention, thanks to the growing use of this material. Mechanical simulations deliver poor results for this material, mainly because of its complex internal geometry. In-situ X-ray Computed Tomography (XCT) testing coupled with digital volume correlation (DVC) is a powerful alternative experimental method for characterising the mechanical behaviour of composite materials [1-3] such as CFRTP-SMC materials, . Within this study, the focus was on the failure behaviour during the loading of this material.
The in-situ XCT test was performed at the KU Leuven XCT Core Facility, which provides a large choice of powerful scanners for this study. The TeScan UniTOM XL scanner (230 kV/300 W X-ray tube) combined with the in-house modified loading device Deben CT 5000 (maximum load of 5 kN) was used to carry out the test. The test was subdivided into three different loading steps leading up to the failure of the material. After each desired load level was reached, a scan was performed. Five different samples were tested. The first two samples had a similar microstructure, and their results were used to validate the experimental method and provide statistical representativity . The other three samples were used to study how fibre length influences both the internal geometry and failure characteristics of CFRTP-SMC. To do so, the samples are composed of different carbon fibre strand lengths, which are respectively 10 mm, 20 mm and 30 mm.
The DVC and image processing parts were realised in the Thermo Scientific Amira-Avizo 2023.1 software. The DVC results have enabled a new path to investigate damage mechanisms in this type of material by linking the microstructure with the strain localisations and the microcrack initiation area. This provides important new information that helps understand the material behaviour. Successful tests were conducted on all the samples, resulting in 3D quantitative data and visual output on the evolution of the microstructure of the material, such as displacement and strain maps (Figure.1.d.e), fibre/strand orientations (Figure.1.f) and porosity (Figure.1.g).
Figure.1. a) In-situ testing setup, b) XCT 3D volume of the sample (number 5, 30 mm fibre length), c) Tensile curve obtained during the in-situ test, d) Vertical displacement field, e) First principal strain mapped on a 3D volume of the sample, f) Fibre orientation on the YZ plan, g) Local pore density map on the YZ plan, h) Stress – Average axial strain curve
The in-situ XCT test was performed at the KU Leuven XCT Core Facility, which provides a large choice of powerful scanners for this study. The TeScan UniTOM XL scanner (230 kV/300 W X-ray tube) combined with the in-house modified loading device Deben CT 5000 (maximum load of 5 kN) was used to carry out the test. The test was subdivided into three different loading steps leading up to the failure of the material. After each desired load level was reached, a scan was performed. Five different samples were tested. The first two samples had a similar microstructure, and their results were used to validate the experimental method and provide statistical representativity . The other three samples were used to study how fibre length influences both the internal geometry and failure characteristics of CFRTP-SMC. To do so, the samples are composed of different carbon fibre strand lengths, which are respectively 10 mm, 20 mm and 30 mm.
The DVC and image processing parts were realised in the Thermo Scientific Amira-Avizo 2023.1 software. The DVC results have enabled a new path to investigate damage mechanisms in this type of material by linking the microstructure with the strain localisations and the microcrack initiation area. This provides important new information that helps understand the material behaviour. Successful tests were conducted on all the samples, resulting in 3D quantitative data and visual output on the evolution of the microstructure of the material, such as displacement and strain maps (Figure.1.d.e), fibre/strand orientations (Figure.1.f) and porosity (Figure.1.g).
Figure.1. a) In-situ testing setup, b) XCT 3D volume of the sample (number 5, 30 mm fibre length), c) Tensile curve obtained during the in-situ test, d) Vertical displacement field, e) First principal strain mapped on a 3D volume of the sample, f) Fibre orientation on the YZ plan, g) Local pore density map on the YZ plan, h) Stress – Average axial strain curve