Issue #11 - December 13th, 2007
Software Suite for Durability, Damage Tolerance, and Life Prediction
Augments FEA Solvers MSC Nastran*, ABAQUS, ANSYS & LS-DYNA
* Best Performance and Verified Solutions with MSC Nastran
This Week's Feature Composite Example
Composite T-Joint Design Analysis
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GENOA-PFA is virtual testing software tool simulating both the detailed micro and macro failures occurred in a composite structure throughout the entire loading process. It can greatly reduce the experimental investigation effort and cost involved in structural design. A British Naval composite joint [1, 2] was employed to demonstrate the application of GENOA-PFA in composite structure durability analysis and design.
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| Figure 2 - Configuration and laminate layups of the British Naval composite joint [1]. |
Configuration of the T-Joint and the FEM - The joint is comprised of two FRP overlaminates bonded to either side of a web plate and then bonded to the base plate or flange (Figure 1). These overlaminates form a boundary angle connection and are comprised of alternating polyester/E-glass woven roving (WR) and chopped strand mat (CSM) layers. The gap within the boundary angle is filled with a compatible resin. The members being joined are comprised solely of polyester/E-glass woven roving. There are 14616 solid elements in the British joint model (Figure 2). The loading condition is three point bending. The load type is forced displacement.
Simulation Results - The joint performance was simulated and the failure mechanism, which occurred in the joint, was identified. Figure 3 illustrates the comparison between the simulated and tested load-deflection relationship of the joint. The two results agree reasonably well for both damage initiation and final fracture loads.
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| Figure 3 - Comparison between simulated and tested load-deflection relationship. |
The damage initiated as tensile- driven delamination in the fillets at the juncture area, where the interlamina tensile stress was the largest under the bending condition. Then the delamination failure propagated through the fillet thickness due to stress redistribution to the undamaged layers from the failed layers. The delamination in the fillets reduced their contribution to bending resistance, which finally resulted in the fracture of the flange at the end of the loading process. The entire simulated damage and fracture process of the joint is illustrated in Figure 4 where red areas represent the damage.
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| Figure 4 - Simulated failure process of the British Naval joint. Red areas represent the failure which was caused by interlamina tensile stress (delamination). |
Conclusions
GENOA-PFA computed detailed laminate failure in the composite joint throughout the entire loading process. The load capacity of the British Naval joint was accurately predicted and its underlying failure mechanism was clearly identified, namely, delamination due to interlamina tensile stresses. Hence, GENOA-PFA is a useful virtual testing tool for optimal design of composite structures, e.g. for a composite joints, the fillet radii and thickness can be optimized to reduce the delamination failure and thus maximize the joint durability.
References:
1. Cody Godines, Frank Abdi, Steven Kiefer and Keith Kedward, "Simplified Analytical Procedure for Prediction of Fracture Damage in Composite Structures", ASTM COMMITTEE-D30 Symposium on Joining and Repair of Composite Structure March 17-18, 2003 Kansas City, MO. Click here to read technical publication.
2. Phillips, H.J., and Shenoi, R.A., "Damage Tolerance of Laminated Tee Joints in FRP Structures", Composites Part A - Applied Science and Manufacturing, Vol. 29, No. 4, pp. 465, 1998. Click here to read technical publication.
Did You Know?
Probabilistic Progressive Failure Analysis
GENOA's Probabilistic Progressive Failure Analysis capability enables the prediction of structural reliability in presence of uncertainties in fabrication parameters, cure, material, geometry, and loading. First, perform low fidelity probabilistic analysis to identify influential random design variables. Second, reduce the list of variables to include critical ones and perform high fidelity simulation (e.g. Monte Carlo) to obtain a measure of reliability. As additional benefits, you will obtain a database of competing designs to improve the product performance and reduce the number of unnecessary tests. For more information on this feature and trying out GENOA through our demos, please contact info@ascgenoa.com.
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