Evaluation of the Sensitivity of Various Reinforcement Patterns for Structural Carbon Fibers to Open Holes during Tensile Tests

Abstract

This paper is devoted to the experimental study of polymeric composite specimens, with various types of reinforcement, in order to evaluate the breaking strength of specimens with open holes when undergoing uniaxial compression and tensile tests. Four types of interlaced 3D woven preforms were considered (orthogonal, orthogonal combined, with pairwise inter-layer reinforcement, and with pairwise inter-layer reinforcement and a longitudinal layer), with a layered preform used for comparison. Tensile tests of solid specimens without a hole, under ASTM D 3039, and of specimens with an open hole, under ASTM D 5766, were carried out using the Instron 5989 universal electromechanical testing system. Movements and strains on the specimen surface were recorded using a Vic-3D contactless optical video system and the digital images correlation method (DIC). For all the series of carbon fiber tension specimens, strain and stress diagrams, mechanical characteristics, and statistical processing for 10 specimens were obtained. The paper evaluated deformation fields for certain points in time; the obtained fields showed an irregular distribution of deformation and dependency on types of reinforcing fibers. A coefficient of strength variation is introduced, which is defined as a ratio of the ultimate stress limits obtained on solid samples with and without open holes. Within the framework of ASTM D 5766, when calculating the ultimate stress, the hole is not taken into account, and the paper shows that for certain structures a hole cannot be excluded. The hole size must not be neglected when calculating the ultimate stress.

Stability of Postcritical Deformation of CFRP under Static ±45° Tension with Vibrations

“…Researchers give preference to the non-contact optical video system VIC-3D during performing shear tests in accordance with various ASTM [ 32 , 33 ]. There is a research [ 34 ] that presents static tests with the results of unloadings for thermoplastic composite samples prepared in accordance with ASTM D3039.…”

Mechanical behavior of fiber-glass plastic with hole pattern using digital image correlation and acoustic emission methods

“…In study [12], modeling of a composite (WFKC) with multiple holes was carried out and compared with the experiment. In non-staggered plates, the maximum stresses occur in the outermost holes [13][14][15]. In staggered hole arrangement, the fracture depends on the smallest cross-sectional area in the direction perpendicular to the plane axis.…”

Deformation Behavior of Single Carbon Fibers Impregnated with Polysulfone by Polymer Solution Method

“…Elementary carbon and glass filaments are characterized by deformations upon destruction of less than 1%, and deformations lie in the range from 1 to 5% in fibers consisting of 1000–24000 filaments, the elongation at destruction due to the sliding of individual filaments in the absence of interaction along the side surfaces. In this case, the deformations of thermoplastic polymers acting as a matrix, at which their flow begins, lie in the range from 1 to 20%, and the flow occurs at stresses at the level of 40–100 MPa [ 28 , 29 ].…”