Non-destructive measurement of fiber mass content of glass fiber sheet molding compound using Terahertz radiation

Measurement ◽  
2021 ◽  
Vol 168 ◽  
pp. 108386
Author(s):  
Lucas Bretz ◽  
Benjamin Häfner ◽  
Gisela Lanza
Keyword(s):  
Glass Fiber ◽  
Terahertz Radiation ◽  
Mass Content ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Fiber Sheet ◽  
Destructive Measurement ◽  
Non Destructive

scholarly journals Direct Fiber Simulation of a Compression Molded Ribbed Structure Made of a Sheet Molding Compound with Randomly Oriented Carbon/Epoxy Prepreg Strands—A Comparison of Predicted Fiber Orientations with Computed Tomography Analyses

2020 ◽  
Vol 4 (4) ◽  
pp. 164
Author(s):  
Jan Teuwsen ◽  
Stephan K. Hohn ◽  
Tim A. Osswald
Keyword(s):  
Computed Tomography ◽  
Detailed Comparison ◽  
Micro Computed Tomography ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Discontinuous Fiber ◽  
Orientation Tensors ◽  
Fiber Sheet ◽  
Local Fiber ◽  
Good Agreement

Discontinuous fiber composites (DFC) such as carbon fiber sheet molding compounds (CF-SMC) are increasingly used in the automotive industry for manufacturing lightweight parts. Due to the flow conditions during compression molding of complex geometries, a locally varying fiber orientation evolves. Knowing these process-induced fiber orientations is key to a proper part design since the mechanical properties of the final part highly depend on its local microstructure. Local fiber orientations can be measured and analyzed by means of micro-computed tomography (µCT) and digital image processing, or predicted by process simulation. This paper presents a detailed comparison of numerical and experimental analyses of compression molded ribbed hat profile parts made of CF-SMC with 50 mm long randomly oriented strands (ROS) of chopped unidirectional (UD) carbon/epoxy prepreg tape. X-ray µCT scans of three entire CF-SMC parts are analyzed to compare determined orientation tensors with those coming from a direct fiber simulation (DFS) tool featuring a novel strand generation approach, realistically mimicking the initial ROS charge mesostructure. The DFS results show an overall good agreement of predicted local fiber orientations with µCT measurements, and are therefore precious information that can be used in subsequent integrative simulations to determine the part’s mesostructure-related anisotropic behavior under mechanical loads.

scholarly journals CHARACTERIZATION OF THE FRACTURE MECHANICAL BEHAVIOR OF C-SMC MATERIALS

2018 ◽  
Vol 18 ◽  
pp. 1 ◽  
Author(s):  
Martin Tiefenthaler ◽  
Philipp S. Stelzer ◽  
Chi N. Chung ◽  
Volker Reisecker ◽  
Zoltan Major
Keyword(s):  
Carbon Fiber ◽  
Tensile Tests ◽  
Representative Specimen ◽  
Carbon Fiber Composites ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Compound C ◽  
Specimen Width ◽  
Fiber Sheet ◽  
Point Bend

The fracture mechanics of random discontinuous Carbon Fiber Sheet Molding Compound (C-SMC) materials compared to traditional carbon fiber composites are not well understood. An experimental study was carried out to characterize the fracture behavior of such C-SMC materials. Mode I tests, using double cantilever beam specimens, and mode II tests, adopting the four-point bend, end-notched flexure configuration, were performed. Results show high variations in the forcedeflection responses and scatter in the fracture toughness properties GIc and GIIc, due to the complex mesostructure defined by random oriented carbon fiber chips. To investigate the influence of the mesostructure, tensile tests with varying specimen width and thickness were assessed by stochastic measures to find the representative specimen size.

scholarly journals Experimental Investigation on the In-Plane Creep Behavior of a Carbon-Fiber Sheet Molding Compound at Elevated Temperature at Different Stress States

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2545
Author(s):  
David Finck ◽  
Christian Seidel ◽  
Anika Ostermeier ◽  
Joachim Hausmann ◽  
Thomas Rief
Keyword(s):  
Elevated Temperature ◽  
Carbon Fiber ◽  
Creep Strain ◽  
Strain Rates ◽  
Molding Compound ◽  
Sheet Molding Compound ◽  
Tension And Compression ◽  
Fiber Sheet ◽  
Stress States ◽  
Carbon Fiber Sheet

The creepage behavior of one thermosetting carbon fiber sheet molding compound (SMC) material was studied applying in-plane loading at 120 °C. Loads were applied in bending, tension and compression test setups at the same in-plane stress level of 47 MPa. Different creep strain rates were determined. The creep strain rate in flexural loading was significantly higher than in tensile loading. The test specimens in compression loading collapsed within minutes and no findings regarding the creep strain rates were possible. Overall, it was observed that the thermosetting press resin of this industrially used material had only little creep load bearing capacity at the mentioned temperature when loaded in mixed stress states. The test data has high usage for estimating design limits of structural loaded SMC components at elevated temperature.

scholarly journals Creep-Induced Screw Preload Loss of Carbon-Fiber Sheet Molding Compound at Elevated Temperature

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3598 ◽  
Author(s):  
Finck ◽  
Seidel ◽  
Hausmann ◽  
Rief
Keyword(s):  
Carbon Fiber ◽  
Testing Machine ◽  
Fiber Reinforced Polymers ◽  
Element Analysis ◽  
Reinforced Polymers ◽  
Molding Compound ◽  
Test Setup ◽  
Sheet Molding Compound ◽  
Fiber Sheet ◽  
Optical Strain

The application of chopped-fiber reinforced polymers in screwed connections at high temperatures raises the question of creep under long-term loading. While up to now thermoplastic materials have mainly been the focus of attention when it comes to creep, this paper shows that thermoset carbon-fiber SMCs (sheet mold compounds) can also be affected by this phenomenon. Screwed connections were investigated regarding their loss of preload force at 120 °C ambient temperature. Additionally, strain–time diagrams were recorded at different stress levels at 120 °C in a creep test setup of a universal testing machine by using optical strain tracking of SMC coupons. The transverse modulus under compression in thickness direction was determined in the same test setup. For data application within a FEA (finite element analysis) software power law curves according to Norton–Bailey creep law were fitted in the strain–time graphs. The applicability of the obtained creep law was crosschecked with a test carried out on the loss of preload force of a screwed connection. The developed simulative methodology offers the possibility to simulate various mounting situations of the bolted connection and to investigate measures against the loss of preload force easily. A promising possibility to limit the loss of preload force due to creep was simulatively evaluated.

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