Keywords

Abstract

Finite element methods; 

 Low-speed impact; 

Load-bearing capacity; 

Delamination, 

Barely visible impact damage

In this paper the load-bearing capacity of a stiffened stringer panel made of polymer composite materials (PCM) reinforced by intermediate modulus carbon fiber under compression after impact was investigated. Computational-experimental investigations were conducted to assess obtained results where stringer panel was loaded to failure. In this paper, a computational and experimental method for modeling the compression after Impact and failure mode for single-span composite panels with barely visible impact damage (BVID) is proposed based on the building block approach. The above-mentioned approach implies step-by-step test series coupled with simulations which are carried out on each stage gradually introducing larger and structurally more sophisticated test samples. That approach serves as the base for design of composite structures by means of increasing the number of smaller test samples and carrying out a lot of simulations in order to reduce the margin of error and to reduce the number of large test structures (wing, fuselage, etc.) required for proof of compliance of the proposed airframe to available design objectives thus cutting the cost of experimental program. Further the model of material behavior was developed considering combined loading caused by growth of cracks and delaminations. For that material model a series of coupon tests were performed to refine elastic and strength parameters of material. Consequently, a ply-by-ply solid finite element model (FEM) of the stiffened two-stringer panel with cohesive interface behavior was developed. Test samples of the stiffened panels made by vacuum resin infusion were subjected to impact damage between the stringers followed by compression in the testing machine with two edges fixed as cantilever beams. Robustness of the proposed simulation method and suggested modelling approach was confirmed by similarity of obtained numerical results and experimental data as well as the similarities of the failure mode and state upon failure.

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