Abbreviations
CFRP	carbon-fibre-reinforced plastics,
DIC	digital image correlation,
DLJ	double-lap joint,
FEM	finite element method,
GFRP	glass-fibre-reinforced plastics,
Variables
A0, A1, A2	constants of theoretical solution of DLJ,
b	width of sample,
C1, C2	stiffness of adherend and overlap, respectively,
E	Young stiffness modulus,
F	applied tensile force,
Fmax	maximal applied value of tensile force during fatigue test,
fu	ultimate tensile strength,
v	tensile speed,
G	shear modulus,
g 0	adhesive thickness,
g 1	adherend thickness,
g 2	overlap thickness,
i	number of samples
Kt	stress concentration factor,
L	length of one side of DLJ joint,
Lsp	space between inner parts of DLJ,
N1, N2	forces in adherend and overlaps in particular cross-section, respectively,
Nf	number of cycles to failure,
R	stress ratio,
ux	elongation of sample in tension direction,
YeH	Yield limit,
εTOT	total strain of sample in tension direction,
εx	major strain in tension direction,
εx,over,cent	strain in middle cross-section of overlap,
ν	Poisson’s ratio,
δinc	ratio of increase of fatigue life of reinforced sample in relation to not reinforced one,
θ	fibre angle orientation in layers with respect to tension direction,
σ	peel stress in adhesive,
τ	shear stress in adhesive,
τadh	adhesive shear strength,
τavg	average shear stress in adhesive,
τavg,FAT	maximal applied value of average adhesive shear stress during fatigue test,
γ	shear deformation.