Damage Assessment and Repair Strategies
Composite Repair of Timber Structure
This research suggests a new approach to the use of composite materials technology for the repair of timber structural members. Due to low aspect ratios, of the typical railroad bridge span timbers, stiffness degradation can be related to the decrease in the shear performance of the beam. To rejuvenate these beams the proposed approach focuses on overcoming the loss of shear properties by inserting fiberglass rods from the bottom to the top of the beam, through the areas of damage. The concept includes the injection of an adhesive during the process of insertion, which not only bonds the reinforcing rods in-place, but also fills adjacent cracks. To support this rejuvenation approach, scale beam testing has been carried out with a variety of reinforcement cases being evaluated. The overall result has been extremely positive, with test beams showing strong recovery of flexural properties through the addition of fiberglass shear spikes and an improvement in the strain to failure.
Impact Fatigue of Composites
Testing of adhesive joints between metal inserts and filament wound tubes, as well as impact of flat plate specimens has been performed. Damage is evaluated using waveform analysis and microwave NDT. This effort has resulted in the ability to determine adhesive and bondline parameters for joints operating under conditions of high-cycle impact. Various adherend surface modifications were performed as well as investigation of different adhesive thicknesses. Testing was performed to a maximum of 1,000,000 cycles.
Damage Growth in Reinforced Composites
Research utilizing impact-fatigue test equipment to generate high-cycle cumulative low energy impact damage. This work has indicated that very low levels of damage can be monitored in fiberglass composites and that the growth can be tracked. Microwave NDT has enabled visual maps to be generated which indicate the location and severity of damage. Vibratory test evaluation has confirmed the data seen in microwave maps, but can be performed in a continuous fashion. This project is aimed at determining the mechanisms of damage initiation and growth and ways to monitor damage in real time.
- Radford, D.W., VanGoethem, D., Gutkowski, R.M., and Peterson, M.L., “Composite Repair of Timber Structures”, Construction and Building Materials, Vol.16, 2002, pp.417-425.
- Barber, B.W. and Radford, D.W., “Impact Fatigue Behavior of Composite Tube/Metal End Fitting Bonded Joints”, Composites Engineering, Vol. 3, No.1, 1995.
- Radford, D.W., VanGoethem, D.J., Peterson, M.L., and Gutkowski, R., “Composite Repair of Timber Structures”, Structural Faults and Repair 2001, London, England, July 4 – 6, 2001.
- Radford, D.W., Peterson, M.L., and VanGoethem, D.J., “Composite Repair of Timber Structures”, Society of Experimental Mechanics Annual Conference on Experimental Mechanics, Portland, OR, June 4 – 6, 2001.
- Melo, J.D.D. and Radford, D.W., “Evaluation of Damage Initiation using Sub-Scale Flexure Testing”, Society of Experimental Mechanics Annual Conference on Experimental Mechanics, Portland, OR, June 4 – 6, 2001.
- VanGoethem, D.J. and Radford, D.W., “A Sub-Scale Flexure Test for High Modulus Composites”, 31st International SAMPE Technical Conference, Chicago, IL, Oct. 26 – 30, 1999.
- Radford, D.W., Olivero, D.A., Lukes, S. and Zoughi, R., “Microwave Nondestructive Investigation of Multiple Impacted Composite Laminates”, ICCM-10, Vancouver, Canada, August 14 – 18, 1995.
- Radford, D.W. and Barber, B.W., “Impact Fatigue Behavior of Composite Tube/Metal End Fitting Bonded Joints”, First International Conference on Composites Engineering (ICCE/1), New Orleans, LA, August 28 – 31, 1994.
- Radford, D.W., Ganchev, S.I., Qaddoumi, N., Beauregard, G. and, Zoughi, R.,”Millimeter Wave Nondestructive Evaluation of Glass Fiber/Epoxy Composites Subjected to Impact Fatigue”, International Symposium on Optics, Imaging, and Instrumentation, SPIE, San Diego, CA, July 24 – 29, 1994.
- Zoughi, R., Ganchev, S.I., Bhattacharyya, J., Gray, S. and Radford, D.W., “Microwave Diagnosis of Carbon Black Rubber Compounds and Porosity Estimation in Composites”, MRS Spring ’94 Conference, San Francisco, CA, April 4 – 8, 1994.
- Radford, D.W. and Teghtsoonian, E., “Fracture Toughness of Carbon Fibre-Epoxy Composites”, International Conference on Testing, Evaluation and Quality Control of Composites, Surrey University, Guildford, England, September 1983, Editor: T. Feest.
- Barber, B. “Impact Fatigue Behavior of Composite Tube/Metal End Fitting Bonded Joints”, MS Thesis, Colorado State University, Summer 1994.