Compression failure of unidirectional glass-fibre-reinforced plastics

For the application of glass-fibre-reinforced plastics (GRP) in service under compression loads it is advisable to make them by using special fibres of 19-μm diameter, which raises their compression strength by 25–30% in comparison with GRP based on standard fibres of 8-μm diameter. Such fibres are still sufficiently workable for processing on improved equipment. The principal failure mechanism under compression of GRP based on thin fibres, of 8–20 μm diameter, is splitting and buckling of the outer layers. The use of fibres of 130-μm diameter leads to suppression of splitting. In this case fibre microbuckling is the dominant failure mechanism. Special testing methods permit observation of the failure caused by microbuckling even in GRP reinforced with fibres of 19-μm diameter. Increasing Young's modulus, strength and rigidity of the matrix leads to higher compression strength, whereas increasing the porosity level causes a substantial reduction of the compression strength.