On stability and damage behavior of asymmetric sandwich panels under uniaxial compression

Abstract

In practical applications, asymmetric sandwich panels with tapered and junction regions are frequently used. Under uniaxial compressions, asymmetric sandwich panels are collapsed with complex failure mechanism, and its mechanical behaviour is affected by tapered regions. For structure safety consideration, it is necessary to systematically investigate the stability and damage behavior of full-scaled asymmetric sandwich panels under uniaxial compression experimentally and numerically. For comparison, symmetric sandwich panels were also studied. Quasi-static compression tests and numerical modeling were conducted. Experimental data were sufficiently recorded and carefully analyzed. Meanwhile a nonlinear finite element model was advanced for evaluating stability and predicting failure behaviours and load-bearing capacity of test specimen. Comparisons between numerical predictions and experimental measurements showed that a good agreement was achieved. The tapered region had significant influence on stability behavior and load-bearing capacity. It intensified the asymmetry and introduced additional bending moments into asymmetric sandwich panels and thus caused early local buckling. Thicker core thickness enhanced the structural stiffness and load-bearing capacity. Large amounts of matrix cracking, fibre push-out and core-skin delamination were captured in asymmetric sandwich panels. Overall, buckling occurred in symmetric sandwich panels instead of local buckling in asymmetric sandwich panels, and brittle fibre breakage dominated the failure.

Post-buckling behavior and failure analysis of asymmetric sandwich panels under uniaxial compression

“…The sign change in slope can serve as an indicator of buckling. 17 Initially, the strains in WFS and SFS exhibit a linear increase with the applied load. After buckling, the strain-load curves in the SFS become non-linear.…”

“…When composite sandwich structures are subjected to compression loads, instability becomes one of the failure modes. Our preliminary research 17 showed that ASPs could still bear significant loads after buckling. The ultimate failure of ASPs was resulted by the combined effects of buckling, core shear, skin delamination, skin/core debonding, and stress concentration at the junction region.…”

“…The specimen size, materials of face sheets and core are different from the ones in. 17 The thickness of a single ply is 0.22 mm. The material properties of the face sheets and core are listed in Tables 1 and 2.…”

“…Since the core mainly bears shear load, shear damage is the main failure mode of the core. 17 Hence, shear damage model 31 is applied to predict the failure of PMI foam. The criterion for shear damage onset is given by.…”

Composite sandwich panel closeout analysis and test

“…2 Investigations of tapered sandwich structures have attracted researchers' interests in the past. [3][4][5][6][7][8][9] A review of composite sandwich structures for aeronautical applications is presented by Castanie et al 10 A variety of nacelle composite structures include sandwich panels that contain closeout design configurations. A closeout (ramp) is formed at the region where a sandwich panel transitions to solid laminates.…”