Delamination buckling and growth phenomena in stiffened composite panels under compression. Part I: An experimental study

Abstract

An experimental investigation has been carried out on skin delaminations buckling and growth phenomena in stiffened composite panels subjected to compression loading. Optical fibers have been used to monitor the delamination-related phenomena. The optical fibers have been embedded in the skin close to an artificial delamination following paths with minimum length, satisfying the grating sensor locations and direction requirements and fulfilling specific embedding/ integrity constraints. The stiffened panel has been also instrumented with back-to-back strain gauges in skin and stringer locations to acquire additional information on delamination and panel buckling and on delamination growth. Finally, a lock-in thermography inspection activity has been performed at different levels of the applied compressive load to acquire information on the delamination buckling and growth shapes. The performed experimental activity was aimed to study the delamination-related phenomena by comparing experimental data obtained from different sources focusing on delamination growth initiation and delamination growth stability.

Interfacial delamination in glass-fiber/polymer-foam-core sandwich composites using singlemode–multimode–singlemode optical fiber sensors: Identification based on experimental investigation

“…Since the diameter of the optical fibers is nearly the same as that of the glass fiber materials used as face sheets, introduction of these materials at the time of construction does not induce any significant stress concentrations in nearby regions. Fiber Bragg grating (FBG) sensors are widely used in sandwich composites [6–11] and stiffened laminated composites [12–14] for mechanical strain and temperature sensing. But the method of writing of Bragg grating in optical fibers is costly, and therefore widespread usage of the sensor material for large structural components may not be cost-effective.…”

Experimental and numerical analysis of repaired stiffened carbon fiber-reinforced plastics panels under compression

“…Many of the published works focus on the influences of geometric parameters such as panel thickness 3 and the dimension of stiffeners 4 on the buckling and post-buckling behaviors of stiffened composite panels in axial compression experiments. Riccio et al 5 performed a series of experiments to study the delamination buckling and growth phenomena of composite stiffened panels with initial delamination subjected to compressive loading. Orifici et al 6 studied the damage growth and collapse behaviors of composite stiffened panels through compressive tests.…”

Characterisation of the impact induced damage in composites by cross-comparison among experimental non-destructive evaluation techniques and numerical simulations

“…Generally, expensive experimental campaigns are necessary to determine material property and to better appreciate the failure mechanisms. [1][2][3][4][5][6][7][8] Indeed, as demonstrated by experimental tests, specimen impact response can be influenced by different parameters such as microstructure and hygro-thermal conditions. 9 In literarure 10,11 the influence of the punch size on the response of the composite specimen in terms of stiffness, peak force, deflection, and energy dissipations is experimentally investigated.…”

“…Several studies about impact phenomena, in literature, introduce failure predictive models and the associated underlying critical aspects related to the impact events. [4][5][6][7][8][9][18][19][20] An interesting overview on numerical models for the prediction of onset and growth of intra-laminar damage is given in literature [20][21][22][23][24][25][26][27][28][29][30] where limitations of the stress-based continuum damage models, adopted for the fibre breakage and matrix cracking prediction, in the presence of localised failure phenomena, involving localised stress and material discontinuities, are pointed out. This is the reason why intra-laminar damage onset and growth is usually predicted by means of CDM (Continuum Damage Models), introducing a degradation factor to take into account the mechanical material properties variations.…”