1. Adhesive Bonding of Composite Joints PhD Project Ian Campbell RP/Composites Facility University of the Witwatersrand

2. Slide 2 © CSIR 2006 www.csir.co.za Why Adhesive Bonding? Proliferation of composite structural equipment in many fields Advantages Speed of manufacture Uniform stresses High strength Repair patches

3. Slide 3 © CSIR 2006 www.csir.co.za Problems Environmental effects Moisture diffusion and absorption Thermal changes Adhesive property changes Stress analysis Fatigue Creep

4. Slide 4 © CSIR 2006 www.csir.co.za Typical Bond Configuration Scarf Joint Single Lap Joint adhesiveload Composite adherend

5. Slide 5 © CSIR 2006 www.csir.co.za Factors Affecting Bond Strength Surface preparation and cohesion Bond thickness Composite adherend layup Adherend material properties Residual stresses

6. Slide 6 © CSIR 2006 www.csir.co.za Modelling Methods Analytical Finite Element Methods Rayleigh-Ritz Method

7. Slide 7 © CSIR 2006 www.csir.co.za Finite Element Methods Elastic model Non-linear elements – Elastic-plastic Spring elements

8. Slide 8 © CSIR 2006 www.csir.co.za Experimental Methods Strain gauges Photo-elasticity Surface coating crack analysis Microscopy

9. Slide 9 © CSIR 2006 www.csir.co.za Typical Specimen Strain gauges

10. Slide 10 © CSIR 2006 www.csir.co.za Comparison Strain distribution at 780 N 0.00E+00 5.00E-04 1.00E-03 1.50E-03 2.00E-03 2.50E-03 3.00E-03 3.50E-03 4.00E-03 00.050.10.150.20.250.30.35 Location Strain Spring model Experiment Elastic –plastic model

11. Slide 11 © CSIR 2006 www.csir.co.za Photoelasticity -Reflective film attached to sample -Limited resolution

12. Slide 12 © CSIR 2006 www.csir.co.za Proposed Solutions Microscopy for strain measurement Rayleigh-Ritz modelling methods