Mechanical Properties of GFRPs Exposed to Tensile, Compression and Tensile–Tensile Cyclic Tests

Abstract

Currently there are many applications for the use of composites reinforced with fiberglass mat and fabrics with polyester resin: automotive, aerospace, construction of wind turbines blades, sanitary ware, furniture, etc. The structures made of composites have a complex geometry, can be simultaneously subjected to tensile–compression, shear, bending and torsion. In this paper we analyzed the mechanical properties of a polyester composite material reinforced with glass fiber (denoted GFRP) of which were carried out two types of samples: The former contains four layers of plain fabric (GFRP-RT500) and the second type contains three layers of chopped strand mat (GFRP-MAT450). The samples were subjected to tensile, compression and tensile–tensile cyclic loading. The results highlight the differences between the two types of GFRP in terms of initial elastic modulus, post yield stiffness and viscoelastic behavior under cyclic loading. Thus, it was observed that the value of the modulus of elasticity and the value of ultimate tensile stress are approximately twice higher in the case of GFRP-RT500 than for the composite reinforced with short fibers type GFRP-MAT450. The tensile–tensile cyclic test highlights that the short glass fiber-reinforced composite broke after the first stress cycle, compared to the fabric-reinforced composite in which rupture occurred after 15 stress cycles. The elasticity modulus of GFRP-RT500 decreased by 13% for the applied loading with the speed of 1 mm/min and by 15% for a loading speed of 20 mm/min.

Statistical Analysis of the Mechanical Behavior of High-Performance Polymers: Weibull’s or Gaussian Distributions?

“…This behavior is due to the formation and development of surface microcracks at the final stages of orientational drawing, the so-called kink bands, which are initiators of the most intense crack growth at the deformation stages preceding the sample failure [ 1 , 2 ]. For this reason, in order to correctly estimate the average values of σ , E , and strain at break ( ε b ), σ av , E av , and ε av , which are important characteristics playing a key role in choosing the most appropriate fields for material applications, the number of identical samples to be tested should be increased markedly, from the generally accepted about five [ 5 , 6 , 7 , 8 ] to some dozens, or even hundreds [ 2 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. In this case, the statistical distributions of mechanical properties can also be analyzed, and additional information obtained, for instance, on their conformity to a certain theoretical model (e.g., Gaussian [ 23 ], Weibull’s [ 9 , 10 , 11 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]).…”

Prediction of the Damage Effect on Fiberglass-Reinforced Polymer Matrix Composites for Wind Turbine Blades

“…These results are in good agreement with the mathematical models developed by [ 45 , 46 , 47 ]. The magnitude of the stresses obtained in the four cases of delamination does not exceed the limit of rupture of the composite, which was determined experimentally by the authors in their previous studies [ 27 ]. In [ 31 ], a similar wind turbine blade was investigated experimentally.…”

“…The stresses extracted from the second studied area of the wind turbine blade (towards the top of the blade—area 2) showed a higher increase than those from area 1, by 35%. This proves that an increase in the degree of blade damage, even over a relatively small area (2000 mm 2 ), causes amplification of stresses in the delaminated area, generating the occurrence of stress concentrators and, according to different studies [ 27 , 28 , 29 , 30 , 40 , 41 , 42 ], the crack propagation occurs with an amplification factor that depends on the intensity of the time-varying loading, aggressive environmental conditions, vibrations, etc. Within this part of the paper, the results regarding the stresses of different WTB integrity states are presented.…”

“…Some researchers [ 20 ] studied the problem of delamination of T-type joints between the cover and the stiffening elements inside the blade. According to other researchers [ 21 , 22 , 23 , 24 , 25 , 26 , 27 ], the delamination mechanism consists of separation of plies from each other under loading. The risks of delamination occurrence consist of increasing the failure area due to interlaminar normal and shear stresses, leading to the sudden collapse of the entire structure [ 28 , 29 , 30 ].…”

Simulation of the Hybrid Carbon-Aramid Composite Materials Based on Mechanical Characterization by Digital Image Correlation Method

“…Hybrid composite materials have extensive engineering applications where a high strength to weight ratio, low cost and ease of fabrication are required. They provide improved properties such as tensile modulus, flexural strength and impact strength [ 12 , 14 , 18 , 19 ].…”