Comparison of the modified three‐rail shear test and the [(+45°,−45°)]_ns tensile test for pure shear fatigue loading of carbon fabric thermoplastics

Abstract

A B S T R A C T The (three)-rail shear test is rarely considered for testing of fibre-reinforced composites under pure shear fatigue loading conditions because of all experimental difficulties. However, in this article, a carbon fabric-reinforced PPS is tested using a modified three-rail shear test setup. The results are compared with [(+45 • ,−45 • )] 4s tensile tests with good correspondence. All fatigue experiments were done with R = 0 and the influence of maximum shear stress and frequency is investigated. It can be concluded that an increase in maximum shear stress decreases fatigue lifetime, whereas an increase in frequency increases the lifetime. Before failure, a sudden increase in both temperature and permanent deformation could be detected. Creep tests yielded that the occurring deformation is mainly due to the fatigue loading, rather than due to creep phenomena. E 11 Stiffness of the composite in the warp (0 • ) direction E 22 Stiffness of the composite in the weft (90 • ) direction F Measured force obtained from the tensile machine G 12 Shear stiffness of the composite h Height of the three-rail shear specimen S T Ultimate shear strength of the composite t Thickness of the specimen (both [(+45 • ,−45 • )] 4s tensile as three-rail shear specimen) w width of the [(+45 • ,−45 • )] 4s tensile specimen X T Ultimate tensile strength of the composite Y T Ultimate compressive strength of the composite ε i Strain obtained from strain gauge i in the three-rail shear test ε xx Longitudinal strain in the [(+45 • ,−45 • )] 4s tensile test ε yy Transverse strain in the [(+45 • ,−45 • )] 4s tensile test ε 11 ult Ultimate strain in the warp (0 • ) direction ε 22 ult Ultimate strain in the weft (90 • ) direction γ 12 Shear strain ν 12 Poisson's ratio of the composite τ 12 Shear stress I N T R O D U C T I O N If one wantsto study the in-plane shear behaviour of a composite, a large number of different experimental setups are available. 1,2 Typical examples are the Correspondence: I. De Baere. E-mail: Ives.DeBaere@UGent.be [+45 • /−45 • ] ns tensile test, 3-8 the 10 • off-axis test, 8-11the Iosipescu test, 1,9,10,12 the two-and three-rail shear test, 13-16 torsion of a rod 17 and torsion of thin-walled tubes. [18][19][20][21] From all these tests mentioned above, the most universal method used for the determination of both in-plane shear modulus and shear strength is torsion of a thin-walled 414

On the tension–tension fatigue behaviour of a carbon reinforced thermoplastic part I: Limitations of the ASTM D3039/D3479 standard

“…In a previous study [30], the fatigue behaviour under shear loads has already been discussed. For the tension-tension fatigue tests, the geometry proposed by the D3039/D3039M-00 standard was also considered for specimens with a [(+45°,-45°)] 4s stacking sequence.…”

“…The realigning of the fibres can be seen in a detailed image of specimen N2 (see Figure 14) Figure 14 Illustration of the change in fibre orientation due to the softening of the matrix [30].…”

“…In Figure 13 the specimen N2, on which a 0-50 MPa, 2 Hz fatigue experiment was done, can be compared with another specimen which is still to be tested, but with the same dimensions as specimen N2 had before testing. Figure 13 Un-deformed (top) and deformed (bottom) [(45°, -45°)] 4s specimen [30].…”

Inorganic Nanoparticle-Modified Poly(Phenylene Sulphide)/ Carbon Fiber Laminates: Thermomechanical Behaviour

“…Further, they can attain a high degree of crystallinity and are cheaper than PEEK based laminates. However, to date, few studies dealing with the behaviour of carbon fabrics reinforced PPS laminates have been published [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ], and these were focused on investigating the effect of temperature, hygrothermal aging and thermal cycling on their mechanical performance. It was found that at temperatures higher than the glass transition of these materials, the quality of the fiber-matrix interfacial adhesion significantly decreased, resulting in reduced mechanical properties particularly under off-axis loading conditions, and their behaviour became highly time-dependent due to the viscoelastic nature of the TP matrix [ 6 , 8 ].…”