Issue #2 - July 9th, 2007
This Week's Feature Composite Example
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| Figure 1 - 3D Weave Architecture |
3TEX 3Weave (3D woven fiberglass mat)/vinyl-ester (Dion 9800) composites (Figure 1) have been investigated as a candidate material in the DOE-Delphi-NCC (National Composite Center) Composite Chassis Cross-Member program. One of the most important mechanical properties for qualifying these composites for such applications is the mechanical fatigue longevity. The math-based GENOA methodology effectively tracks the details of damage initiation, growth, and subsequent propagation to fracture, for composite structures subjected to cyclic fatigue, thereby predicting the fatigue life.
The utility of the GENOA technology was demonstrated by predicting premature and extended fatigue lives in tensile mode of various 3TEX 3Weave/Dion composites (Figure 2). The simulated fatigue longevity of 3D woven ISO coupons agrees well with those measured in actual tensile-tensile fatigue tests using the R (minimum-to-maximum stress ratio) value of 0.1 (Table 1). Furthermore, GENOA PFA simulations quantitatively predicted the effect of the void content on premature fatigue failures.
| Table 1 - Comparison between fatigue life cycles for composites with high and low void contents |
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Indeed a 10% volume fraction of void defects reduces the fatigue life of the 3D woven composite by a factor of 40 at the tensile load of 30% composite ultimate strength (Table 1). Finally, the sensitivities of composite fatigue life to manufacturing anomalies were calculated using GENOA Probabilistic PFA for future design of the composite structure (Figure 3). This math-based predictive methodology is currently being used in the DOE-NCC Composite Chassis Cross-Member program.
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| Figure 2 - Failure mechanisms for the tensile-tensile fatigue of the composite tensile test coupon |
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| Figure 3 - Sensitivities of composite fatigue life to its constituent parameters |
Did You Know?
Five Reasons to Use GENOA for Aerospace Applications
- Accurate prediction of loads that produce damage and fracture initiation and propagation in composite/sandwich/metallic structures.
- Assessment of damage initiation and growth under static, impact (low and high velocity), thermo-mechanical fatigue (quasi-static, harmonic, and random), and creep loading.
- Prediction of failure modes (including delamination, fiber micro-buckling, fiber crushing, etc.) in composite structures.
- Simplified representation of all types of composites including tape, 2D-3D weave and braids and stitched (polymers and ceramics).
- Ability to select from a range of competing designs that would improve the product performance and delivery time to market through virtual testing and accelerated certification processes.
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