PSI - Issue 32

S.A. Bochkareva et al. / Procedia Structural Integrity 32 (2021) 334–339 Author name / Structural Integrity Procedia 00 (2019) 000–000

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At point C, a load was set stepwise. This made it possible to set a load being distributed over an arc with the radius of 5 mm. Figure 8 shows the calculated dependences of the flexural stress versus the relative bending deformation corresponding to different CF layouts and levels of adhesion. The latter of 100 % corresponded to the ultimate stresses equal to the yield point. The highest strength was attained for the composite with longitudinal fiber layout (0°/0°), while the lowest for one with the transverse (90°/90°) pattern. With decreasing the level of adhesion down to 20 % the strength of the composites under consideration decreased. In doing so, level of adhesion and presence of discontinuities between inclusions and the matrix played an important role. 3. Conclusions A model of a fiber-reinforced composite was developed taking into account discontinuities, delamination between the binder and inclusions, and composite fracture. On the basis of the developed model the effect of delamination and fracture on the strength properties of PEEK-based composites under different stress states was illustrated. It was shown that increase in the adhesion level between fibers and polymer increased the tensile strength of composites reinforced in the longitudinal direction. However, the elastic modulus was not changed. The proper quantitative estimates were obtained for the composites under consideration. It was found that under stretching of composites reinforced in the transverse direction, the matrix played a decisive role in their effective properties. Increasing the number of fiber-polymer contacts gave rise to strength elevation of the composites. Similar results were obtained for composites reinforced along longitudinal direction under shear. It was shown that with decreasing the number of contact points one can significantly reduce the shear modulus and shear strength. The performed calculations showed the possibility of increasing strength of the composites in bending by several times. It came from increasing the adhesion level and the number of contacts between the fibers and the matrix.

Acknowledgments This research was granted by Russian Science Foundation № 21 -19-00741, https://rscf.ru/project/21-19-00741/».

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