Three-dimensional Non-linear Rate-dependent Numerical Analysis And Experimental Study Of The Thermoplastic Composite AS4/PEEK

In the aerospace industry, thermoplastic composite materials are widely used. Amajority of experimental studies show that AS4/PEEK laminates present distantstrain-rate dependent nonlinear behavior owing to the improvement of the matrixtoughness. The damage of interlaminar delamination is one of the important fracturemodes. In order to clarify the damage mechanism, it is most important to calculate theinterlaminar stresses as well as their distributions and carry out the relativeexperiments.In this paper the three-dimensional anisotropic elastic-plastic analysis is carriedout for the interlaminar stresses at different interfaces of the thick AS4/PEEKlaminates [0/±45/90]2s and [±25]s4 under uniaxial tension. Through thethree-dimensional distribution plots, the distribution characters of the interlaminarstresses at different interfaces are analyzed and the main factors which can lead todelamination are demonstrated. The interlaminar stresses of the thick AS4/PEEKlaminates [0/±45/90]2s and [±25]s4 for different strain rates are computed. The effectsof different strain rates on the interlaminar stresses are studied.The interlaminar stresses of the angle-ply laminates [±θ]s (The values of θ are15,45 and 75 respectively.) for different strain rates under uniaxial tension arecalculated by three-dimensional elastic-viscoplastic analysis. They are given with thethree-dimensional distribution plots. The effects of the variation of the strain rates andthe ply angle on the interlaminar stresses are investigated.Furthermore, the deformations and stresses of the thermoplastic compositelaminates [±25]s4 , [0/±45/90]2s with a hole are calculated through thethree-dimensional elastic-plastic analysis. The three-dimensional distribution plots ofall the points on the middle cross-section and the middle longitudinal section arepresented. Besides, the stress distribution curves of all the points along the hole edgeat different interfaces are got and the dangerous locations are demonstrated.The thick notched thermoplastic composite laminates [0/±45/90]2s are also studiedthrough digital speckle correlation method. The distribution characters of thedisplacements and strains are investigated and the characters of the damage andfracture are examined. The experimental results are compared with the correspondingnumerical simulating ones.In this paper for the three-dimensional elastic-plasticity model andthree-dimensional elastic-viscoplasticity model which can simulate the non-linearbehavior and the strain rate dependence behavior of thermoplastic compositeAS4/PEEK well, two relative finite element procedures are developed by ourselves.Comparing the finite element computing results with the experimental ones in thereference, it can be found that both fit well, which verifies the reliability andeffectiveness of the developed procedures. With the developed elastic-plasticprocedure and the elastic-viscoplastic one, the quantitative research of thedisplacement field, the strain field and the stress field of AS4/PEEK laminates arefinished.