Fiber-reinforced polymer composites (FRCs) are extensively used in various commercial applications such as aerospace, transportation industry, recreational and sporting goods due to their enhanced properties. However, they are costly and are not eco-friendly. Offering competitive properties at a lower cost and improved sustainability, flax fiber-reinforced epoxy composites (FFRECs) are recognized as an attractive alternative to glass fiber polymer composites for various applications.
FFREC parts are produced to their final geometry; still, some machining processes are often unavoidable for technical and quality purposes. However, machining of FFRCs remains challenging due to their heterogeneity and anisotropic nature that induce workpiece damages such as delamination and generate inferior surface finish. In- depth knowledge of their machining processes is vital for reducing these damages and improving their machining quality. Edge trimming is frequently used for geometrical corrections of FRCs; however, only few experimental studies have addressed its application to FFRECs. The complexity of their cutting process requires involving the finite element method (FEM) to study it, but it is impossible due to a lack of adequate material properties. Therefore, this study aims at a comprehensive evaluation of unidirectional (UD) FFRECs to provide their essential material characteristics for finite element modeling of their edge trimming process.
Accordingly, first, UD-FFRECs with unique specifications were molded via resin transfer molding (RTM). Then, test specimens were prepared and tested according to the adapted standard test procedures, initially developed for synthetic FRCs.
Physical properties, including density, specific heat capacity, and thermal diffusivity/thermal conductivity, were determined according to standard test methods.
Strength/stiffness properties under tension, compression, shear, and flexural loading, in longitudinal/transverse directions were evaluated following standard test methods. Also, the failure mechanisms were investigated via fractography. The results are in good agreement with those of the literature, when available, while they mainly show the specific behavior of UDflax composites subject to different solicitation modes.
Proper test specimens were designed and tested for the interlaminar fracture energies in Mode I, Mode II, and Mixed-Mode I/II. The tests were carried out following ASTM standards. The results are in good agreement with literature data for similar cases, where available.
For UD laminates, the application of the conventional test methods for translaminar failure mode is challenging; also, there is no standard method for testing them in compression. Two methodologies were employed, along with an investigation of the fracture behavior and viability of the standard test procedures for FFRECs. First, the composite was tested for translaminar fracture toughness in tension according to the existing ASTM E1922. Then, employing an Infrared Thermography (IRT)-based methodology, as well as ASTM D5045, the translaminar fracture energy of UD-FFRECs in tension and compression was determined. For tension tests, the results of IRT agree with those of ASTM, whereas compression tests showed a significant discrepancy, indicating the inappropriateness of IRT for these tests.
Overall, for a UD-FFREC with unique quality, an in-depth knowledge was developed, and a full set of precise and reliable material properties and fracture energies, fulfilling FEM requirements were generated.
| Date | 7 Dec 2020 |
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| Original language | American English |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Jean-François Chatelain (Supervisor), Gilbert Lebrun (Co-supervisor) & Yves Beauchamp (Co-supervisor) |
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Saadati, Y. (Author),
Chatelain (Supervisor), Lebrun (Co-supervisor) & Beauchamp (Co-supervisor),
7 Dec 2020Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering