Static and Dynamic Characterization of Composite Materials for Future Driveshaft Systems

Open Access
Author:
Henry, Todd Carl
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 04, 2012
Committee Members:
  • Edward Smith, Thesis Advisor
  • Charles E Bakis, Thesis Advisor
  • George A Lesieutre, Thesis Advisor
Keywords:
  • Flexible Matrix Composite
  • FMC
  • Driveshaft
  • Filament Winding
  • Helicopter
Abstract:
A single-piece fiber reinforced composite driveshaft is an attractive advancement over a multiple segmented metallic driveshaft. A composite driveshaft can be optimized to transmit power in a misaligned condition without the use of flexible couplers that add weight and complexity. Using a flexible matrix composite (FMC) for this application seems to be an attractive approach in comparison to a conventional rigid matrix composite (RMC) because of the potentially low energy dissipation and high cyclic strain capacity of elastomeric matrix materials. However, a lack of accurate models for critical strength and elastic properties of FMCs makes it necessary to experimentally characterize these parameters. Characterization of fiber dominated properties is further complicated by the presence of fiber undulations which are manufactured into the part during filament winding. The objective of this research is to develop material characterization tools that provide the necessary inputs for the mechanical design of misaligned laminated composite driveshafts. A [±θ/89/±θ] laminate was devised for the express purpose of evaluating the compressive strength and elastic modulus of the unidirectional composite in the fiber direction—properties which are believed to be strongly affected by fiber undulations. The fiber direction modulus back-calculated using this specimen design applied well to a range of laminates and winding patterns, although the fiber direction strength was found to be highly dependent on winding pattern. An empirical model relating the Young’s modulus of the matrix material to the various quasi-static elastic and strength parameters of interest in shaft design was developed. This model is potentially useful for the rapid screening of candidate matrix materials. Master curves representing the transverse and shear dynamic storage moduli and loss factors versus loading frequency and temperature were created for multiple candidate composites with different matrix stiffnesses. These curves, in conjunction with other properties measured in this investigation, were used as inputs for a previously developed analytical tool for predicting the steady-state surface temperature of a spinning misaligned laminated composite shaft. Predictions from the model were compared to spin test data for several materials and laminates. Good agreement between the predicted and measured temperature increases was obtained for flexural strains up to approximately 2000 µε, which encompasses the range of cyclic strains expected in rotorcraft driveshaft applications. In conclusion, the material characterization methods developed in this investigation have been shown to provide good estimations of all material properties of relevance in the mechanical aspects of driveshaft design.