Prediction of long-term mechanical behaviour of fibre composites from the observation of micro-buckling appearing during creep compression tests

The axial compressive strength and failure time of IM7/977-2 quasi-isotropic viscoelastoplastic laminates are investigated. Effects of non-linear shear behaviour and fibre misalignment are emphasized because they are important strength-limiting factor in those strongly anisotropic composites which fail by local buckling in the shear mode of deformation. We first describe the basic model of Budiansky [Budiansky B, Fleck NA. Compressive failure of fibre composites. J Mech Phys Solids 1991; 41(1): 183–211], the model of Schapery [Schapery RA. Compressive strength and failure time based on local buckling in viscoelastic composites. Appl Mech Rev 1993; 46(2): S221–8] neglecting non-linear effects in the quasi-elastic solution and finally we adapt the model of Slaughter and Fleck [Slaughter WS, Fleck NA. Viscoelastic micro-buckling of fibre composites. J Appl Mech 1993; 60: 802–6] to predict creep compressive strength for any multi angle laminate. The analysis is formulated in terms of general non-linear viscoelastic viscoplastic behaviour within the kink band. Failure is due to the attainment of a critical failure strain or a critical angle ϕr in the kink band.