An investigation into the behaviour of various sized fibre reinforced plastic beams

This thesis reports the results of an investigation into the behaviour of fibre reinforced composite beams of various sizes subjected to flexural loading. The distribution of stress and strain through the depth of glass fibre reinforced composite beams were investigated using three experimental techniques, namely: interlaminar strain gauging, photoelastic coating, and thermal emission (SPATE) . Experimental results indicated that the beam geometry and type of flexural loading influenced the through thickness strains. Comparisons between experimental results and theoretical predictions from classical lamination theory, higher order displacement theory, and finite element analysis were conducted and discussed. The influence of the material quality (voidage) of bi-directional stitched glass fibre reinforced composite beam on beam performance was studied. It became apparent from the tests, that the void content plays a significant part in the strength and the mechanisms leading to failure, especially in shear mode. The influence played by changing the dimensions of uni-directional carbon fibre reinforced composite beams on strength and mode of failure was also investigated. It was shown that, the beam geometry (size) effects both its strength and mode of failure. The gross material failure and the onset of beam failure was predicted using approaches based on both macro mechanical and micro mechanical criteria. These criteria were developed either from experimental observation or extensions of existing failure criteria