Characterization and Modeling of 3D Woven Composites
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Date
2003-06-13
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Abstract
The objectives of this research are: 1.To fully develop the chemical blowing method. 2.characterize 3D woven cellular matrix composites for different fibers and structures. 3. Develop an FEA model simulating elastic properties.
3D woven glass and carbon regular matrix composites (RMC) were fabricated using vacuum assisted resin transfer molding method. 3D woven glass and carbon cellular matrix composites (CMC) were fabricated using chemical foaming method. Fabric preforms were soaked in NaHCO₃ solutions. CMC C1 was soaked in NaHCO₃ solutions once and CMC C2 was soaked twice. Vacuum assisted resin transfer molding was used to fabricate CMC C1 and C2 after the preforms were dried. Prepreg glass CMC materials P were fabricated using prepreg yarns directly.
Density reduction of glass CMC C1 was 11.57%, while that of glass CMC C2 and P was 14.51% and 6.01%, respectively. For carbon composites, higher density reductions were obtained due to lower carbon fiber density. Carbon CMC C1 achieved a density reduction of 25.40% and that of carbon CMC C2 was 24.03%. This reduction was resulted from emptied resin pockets and air bubbles in the yarn bundles.
For Glass composites, all the specimens failed under a brittle failure mode in tensile test. Interfacial debonding, fiber breakage and fiber pullout after breakage were the major failure mechanisms. Glass CMC showed a higher specific modulus than RMC. Four-point bending cannot fracture all glass RMC and CMC specimens in warp direction. All other specimens showed a ductile failure behavior. Fiber/matrix debonding, delamination and yarn fracture in tensile side were observed. Strength of the composite suffered from the foaming process. CMC C1 and C2 showed improved specific tangent modulus in warp direction while CMC P did not show improvement. For weft direction specimens, Glass CMC showed significant improvements at 29.31% to 30.26% for C1 and C2 respectively. For low speed impact test, the radial damage expansion area adjacent to the perforated region was the smallest for the glass RMC R and largest for the prepreg system. The foamed composite resisted the largest number of strikes, and it also dissipated more cumulative energy than the other two systems.
For Carbon composites, all the specimens failed under a brittle failure mode in tensile test. CMC C1 and C2 had higher specific moduli than RMC R. For CMC C1, specific modulus in weft direction improved 19%, while that of warp direction improved 24.9%. For CMC C2, specific modulus increased 9.8% and 22.8% in weft and warp directions, respectively. For specific compression modulus, CMC C1 was 20% stiffer than RMC R in warp direction, while weft direction reached an improvement of 13%. For CMC C2, the improvement was 9% and 25% in warp and weft directions, respectively. Flexural strength and tangent modulus of CMC C1 and C2 were significantly lower than RMC R. However, specific tangent moduli of the cellular matrix composites were similar to that of the regular matrix composites.
An FEA model was developed using the smallest repeating unit cell in 3D orthogonal woven structure. Good agreement between the FEA model and the experiments were found in CMC.
Chemical blowing method was proven to be an effective alternate to physical blowing method. Excess amount of sodium bicarbonate may harm the tensile properties of the composites.
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Keywords
cellular, composites, FEA, 3D woven
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Degree
PhD
Discipline
Fiber and Polymer Science
