Pre-stressed advanced fibre reinforced composites fabrication and mechanical performance
Advanced composite materials have high strength-to-weight ratios, corrosion
resistance and durability and are extensively used in aerospace, energy and defence
industries. This research concentrates on minimising the process-induced residual
stresses, and improving the fibre alignment of composites by employing a fibre prestress
methodology. A novel flat-bed fibre prestress methodology for autoclave processing of composites was developed. This research investigates the effect of fibre prestress on 1)
residual stresses, 2) fibre alignment, 3) static tensile and compression properties and 4)
fatigue behaviour of composites.
Experimental results show that this prestress methodology, on a 16-ply unidirectional E-glass/
913 epoxy composite, reduces the residual strain of the composite from –600 µ? to
approximately zero for a prestress of 108 MPa. The strains measured from optical fibre
sensors were in close agreement with those obtained using strain gauge. The results from
fibre alignment studies showed that fibre prestressing improved the fibre alignment from
20% of fibres aligned to 0 ° degree in non-prestressed composites to 75% of fibres aligned
to 0 ° degree in 108 MPa prestressed composites.
Findings have shown that prestressing is beneficial to the static compressive and tensile performance of composites. The results show that fibre prestressing improves the fatigue
life and resistance to stiffness degradation in the low stress level fatigue region. Also a change in static and fatigue damage mechanism was observed. The improvement in the static and fatigue properties is due to the reduction in residual stresses and fibre waviness.
Overall the fibre prestressing methodology enhances the performance of composites by
increasing the resistance to static and fatigue loading. The thesis also suggests that there is an existence of prestress limits to retain optimal material performance.
Advisor:Badcock, R. A. (supervisor); Hetherington, John G. (supervisor)
School Location:United Kingdom
Source Type:Master's Thesis
Date of Publication:02/01/2006