Fatigue Damage of Composite Laminate under Biaxial Loads

Fatigue of fiber reinforced composites under multiaxial loading

“…Under combined tension and shear loading, a phase shift d xy,x equal to 180 induces a fatigue strength reduction of about 25%, and the strength reduction reaches about 50% in the case of combined cyclic compression and shear. Other results supporting the negative influence of load phase shift have been reported by Ohlson [14] for AE45 or UD carbon/epoxy samples under bending and torsion and by Susuki [25] for [0/45/0/45] s glass/epoxy cruciform specimens.…”

“…Moreover, by testing cruciform samples it is impossible to induce global shear stresses; to do this one can only apply torsion loading to cylindrical specimens. These reasons explain the limited number of experimental programs carried out on cruciform specimens [15,16,18,25,39,49].…”

50th Anniversary Article: Multiaxial Fatigue Testing of Composites: From the Pioneers to Future Directions

“…In the case instead of a unidirectional stacking sequence, the direct effect of transverse stress σ 2 over the normal stress σ 1 can be investigated, and this can be of help for microscopic damage investigation purposes. However, in spite of the comprehensive and careful investigations on fabric reinforced laminates presented in [62] and few other researches [63][64][65][66][67], the results reported so far show how difficult is in general to obtain failure in the calibrated section of the specimens under fatigue. Moreover, stress concentrations due to the milling required to produce the calibrated section are frequently the undesirable sites of damage initiation.…”

“…Phase shift between load components can be another issue of interest in practical applications. Even on this subject, literature indications are very limited and quite contradictory and further investigations and understanding are needed.…”

Comparison of Different Techniques for Strain Monitoring of a Biaxially Loaded Cruciform Specimen

“…To simulate the in‐service behaviour of composite materials in structures, a variety of failure prediction models can be used. The validation of these models based on only uniaxial test data is inappropriate because composite laminates are generally developing multiaxial stress states during real‐life loading conditions [1, 2]. Therefore, biaxial testing has to be considered.…”