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Effects of sustained vibration and high temperature environments on polymer bonded composite materials

Description:

OBJECTIVE: Test hardware and testing methodologies for the evaluation of the effects of sustained vibration and high temperature environments on polymer bonded composite materials 

DESCRIPTION: Polymer bonded composite materials employed in future munitions are expected to endure harsh environments of intense wide-frequency vibration combined with heightened temperatures for long durations (30-60 minutes or more). The Air Force is interested in methods to evaluate the degree of degradation and structural/mechanical changes of polymer bonded composite materials in response to such environments. Samples of suitable composite materials should be insulted with a controlled wide-frequency vibration profile while simultaneously subjected to a controlled temperature environment. The composite material sample should also be monitored via various techniques (infrared thermography, laser Doppler vibrometry, vibration spectrum analysis, high-speed/post-test microscopy, etc.) to evaluate the degradation and internal heat generation of the sample due to the combined effects of the vibration and high temperature environment. 

PHASE I: Design appropriate experimental hardware and testing methodology to hold small (few gram to 2 kg) test samples of polymer bonded composite materials under controlled vibration profiles with frequencies up to 40 kHz and accelerations up to 4 g. During testing the sample should be contained in a temperature controlled enclosure capable of maintaining the air temperature at settings between a minimum of -60ºC and a maximum of 300ºC. Diagnostic techniques such as infrared thermography, laser Doppler vibrometry, vibration spectrum analysis, and microscopy shall be utilized to characterize the degree of degradation of the composite materials under the applied conditions. Efforts should be focused to explore the specific mechanisms of degradation and internal heat generation of the materials due to the combined vibration and thermal conditions (e.g. particle-particle friction, thermal degradation of polymers, viscoelastic heat generation, etc.). 

PHASE II: Develop and implement the experimental designs and methods from Phase I. Extend capabilities of the experimental design to be suitable for large test pieces (up to 10 kg and from 10 kg to 1000 kg, or appropriate intermediate ranges) of energetic composite materials. 

PHASE III: This technology is applicable to the evaluation of the safety and performance of future munitions under harsh vibration and thermal environments, which is of interest to the Air Force and DoD. Commercial interests may include developed tools and techniques central to the area of non-destructive evaluation for monitoring the health of civil and aviation structures and may extend to the evaluation of damage in transported materials, as well as for materials in other high-stress industrial environments. 

REFERENCES: 

1: Woods DC, Miller JK, Rhoads JF. On the Thermomechanical Response of HTPB-Based Composite Beams Under Near-Resonant Excitation. ASME. J. Vib. Acoust. 2015

2:  137(5):054502-054502-5

3:  G. Busse. Nondestructive Evaluation of Polymer Materials. NDT & E Int. 1994

4:  27 (5):253262

KEYWORDS: Vibration, Munitions, Polymers, Thermal Degradation, Composite Materials, Non-destructive Evaluation, Thermography 

CONTACT(S): 

Martin J Schmidt (AFOSR/RTA1) 

(703) 588-8436 

martin.schmidt@us.af.mil 

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