Behaviour of laminated fibre composite sandwich girders

The objective of this work was to determine experimentally the flexural behaviour of laminated composite sandwich beams based on orientation and the number of laminations. The failure modes and loads were numerically modelled and predicted analytically. The sandwich beams were fabricated using a new generation of sandwich composite with biaxial glass fibre/resin skin and an innovative phenolic based core material. The laminated beams were subjected to 4-point static bending tests to determine the strength and failure mechanisms. The beams tested consist of one to four laminates in the flatwise and edgewise orientation. Strains to failure in the face sheets were measured through the use strain gauges and beam deflections were recorded for each specimen. The results of the experimental investigation demonstrated that the laminated sections tested in the edgewise orientation failed at a higher load than those in the flatwise orientation. The flatwise specimens had a brittle type failure. This was primarily due to the compressive failure of the skin followed by debonding between the skin and the core. The vertical skins in the edgewise orientation caused a difference in the failure mode and ultimately facilitated the increase in ultimate strength. The vertical skins prevented the tension cracks in the core from propagating and caused ductile type failure mode through the progressive failure of the skins. The analytical predictions from the constituent material data confirmed the experimental results. The analytical investigation conducted predicted the load deflection behaviour and initial failure loads. The results from the linear numerical modelling are in agreement with those observed in the experimental data. The experimental data established that for a higher number of laminations the beam sections in the edgewise orientation provides an optimal alternative to the flatwise orientation. It was found that the edgewise orientation provides a higher ultimate strength