Utilizing carbon fiber reinforced polymers (CFRP) in design offers advantages including as mass reduction, increased stiffness, enhanced corrosion resistance, improved sound damping, and vibration absorption. The notable strength-to-weight ratio of CFRP has driven its adoption over traditional materials like aluminum and steel in various industries such as aerospace, automotive, and sports. The assembly of "Stack-ups," which are layered assemblies of CFRP and metal components, becomes crucial as CFRP increasingly replaces metallic parts in high mechanical loading structural situations. The high thrust force involved in machining fiber reinforced polymers (FRPs) causes a peel-up and push-out effect on the workpiece, leading to delamination of the plies. This study developed an FE tool to simulate the drilling of FRPs effectively, aiming to validate tool design and enhance the cutting process.
Modeling the impact of fiber orientation in CFRP material on mechanical behavior is essential for optimizing component design and manufacturing. To reduce the exhaustive experimental work related to CFRP material characterization Abaqus Explicit is used to predict the tensile material response through fracture. FEA analyses included mesh size, mass/time scaling, failure models, and cohesive surfaces. Experimental results with the new fixturing-rig show consistent gauge region failure, regardless of fiber orientation. Puck's model accurately predicts fracture force and displacement for parallel fiber orientation. 45 and 90-degree orientations, maximum strain and LaRCO2 models offer better accuracy. Most apparent, was the criticality of cohesive surfaces to predict the nonlinear loading response observed experimentally. Simulations for various fiber layup orientations indicate similar force-displacement signatures, with a notable reduction in failure force at angles between parallel and 45 degrees.
Simulating CFRP mechanical properties under three-point bending to understand cohesive interactions between plies in a laminate was investigated; this capability critical to effectively model the peel-up and push-out problem observed when drilling. A parametric FEA study investigated the affect of mesh size, mass/time scaling, failure models (Hashin, MCT, LaRC02, Maximum Strain, Puck), and cohesive surfaces versus loading response. Experimental results with a larger radius punch show failure on the intended bottom side, facilitating Aramis strain camera recording. Effective mass/time scaling reduces computation time while maintaining accuracy. For perpendicular fiber orientation, all failure models exhibit a similar force-displacement rate. Minimal difference exists among 0-degree models, except for a 4.18% underprediction by LaRC02. At 45 and 90 degrees, Maximum Strain and LaRCO2 models prove more accurate and converge well. The study underscores the need for cohesive surfaces to predict nonlinearity in loading responses for non-parallel bending setups.
A 3D drilling model is developed discussing significance of modelling techniques and considerations. The removal of failed elements creates periodic voids between the workpiece and tool, underlining the importance of proper mesh development. Accurate, computationally efficient models with element lengths of 50-75 µm near the expected failure region were emphasized. Using a discrete rigid body yielded a 42.1% reduction in memory requirements and a 2.81x reduction in time step compared to deformable bodies with rigid constraints. Mass scaling led to over tenfold computation time reduction with a mere 5.3% mass change. Increasing viscosity parameters improved the loading response of CFRP laminate during high-speed drilling. Strain rate strengthening, aligned with literature, increased the load profile by 10.9%. Friction in the CFRP drilling model showed less sensitivity than estimated, with a 4.4% standard deviation.
The FE model once confidently developed, was compared to experiments. The prediction aligned well with experiments, accurately predicting thrust force differences between CD854 and CD856 drills. The CD856 exhibited reduced inter-ply damage, highlighting the advantage of double-angle drill geometry. The CD854's "spur" cutting edge geometry improved hole quality.
The "Stack-up" drilling model effectively predicted thrust force transitions between UD-CFRP and Aluminum layers, confirming the CD854's reduced thrust force when drilling Aluminum, as described by the tool manufacturer Sandvik. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/30469 |
| Date | January 2024 |
| Creators | Hale, Patrick |
| Contributors | Ng, Eu-Gene, Mechanical Engineering |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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