Monitoring the Diameter Changes of Flax Fibre Elements during Twin Screw Extrusion Using X-Ray Computed Micro-Tomography

ABSTRACT

Fiber size aspect ratio is known to impact the mechanical and reinforcement properties of natural fiber-based composites. However, the representation of fiber diameter change occurring during the extrusion process is controversial compared to the length. Fiber elements undergo multidirectional stresses and complex interactions within the extruder, leading to their breakage, which consequently may modulate their reinforcing properties. To better understand these mechanisms, short fiber reinforced polymer composites were prepared from flax fibers and polypropylene matrix (PP) by melt mixing. Five sampling zones were selected along the screws, both in screw conveying elements and inside blocks of kneading discs. X-ray computed micro-tomography, and 3D images analysis were then used for monitoring sample diameter distributions along the screw profile, according to specific twin-screw compounding conditions. The effects of the considered processing condition on fiber bundle diameters decrease along the screw profile are quantified.

摘要

纤维尺寸长宽比对天然纤维基复合材料的力学性能和加强性能有影响.然而，与纤维长度相比，在挤出过程中纤维直径变化的表现形式是有争议的.纤维元件在挤出机内经受多方向应力和复杂的相互作用，导致其断裂，从而可调节其增强性能.为了更好地理解这些机理，以亚麻纤维和聚丙烯基体（PP）为原料，采用熔融共混法制备了短纤维增强聚合物复合材料.在螺杆输送元件和捏合盘的内部块中，沿着螺钉选择五个采样区.然后根据特定的双螺杆复合条件，使用X射线计算机显微断层扫描和三维图像分析来监测样品沿螺杆轮廓的直径分布.量化了所考虑的加工条件对纤维束直径沿螺纹轮廓减小的影响.

KEYWORDS:

• Natural fibre based-composites
• X-ray computed micro-tomography
• 3D image analysis
• twin-screw extrusion

关键词:

• 天然纤维基复合材料
• X射线计算机显微断层摄影术
• 三维图像分析
• 双螺杆挤出

Acknowledgments

This work was supported by the French National Research Agency ‘ANR-12-RMNP-0004ʹ in the frame of the DEFIBREX program, as well as the Competitiveness Cluster Industries & Agro-Ressources (IAR) support. The authors thank Simon Dobosz from INRA for his support with twin screw extrusion, and the ANR for supporting this study through the XyloMat project, XYLOFOREST (ANR-10-EQPX-16) which allowed to fund the X-ray µCT.

Additional information

Funding

This work was supported by the French National Research Agency; Industries & Agro-Ressources (IAR).