Biaxial testing of fibre-reinforced composite laminates

Abstract

Advanced composite material systems are increasingly used in almost every industrial branch. The structural components manufactured from these composite material systems are usually subjected to complex loading that leads to multi-axial stress and strain fields at critical surface locations. The current practice of using solely uniaxial test data to validate proposed material models is wholly inadequate. In order to test closer to reality, a biaxial test bench using four servo-hydraulic actuators with four load cells was developed. Besides the development of the test facility, a mixed numerical/experimental method was developed to determine the in-plane stiffness parameters from testing a single cruciform test specimen. To obtain the strength data an optimized geometry for the cruciform type specimen was designed. For the optimization procedure a full three-dimensional finite element model was used. The numerical results were validated with strain gauge, digital image correlation, and electronic speckle pattern interferometry data. The material system used for the experimental validation was glass fibre-reinforced epoxy with a lay-up [(+45°−45° 0°)4(+45°−45°)] typically used for wind turbine blades.

Strength characterization of glass/epoxy plain weave composite under different biaxial loading ratios

“…A solution to improve the mechanical behavior identification is to use the biaxial test. In fact, it presents a high performance to identify material properties by performing a single test instead of multiple uniaxial tests [2]. In addition, it allows the application of biaxial loadings, closer to the real conditions encountered by the composite structure.…”

Cruciform Specimen Design for Biaxial Tensile Testing of SMC

“…Smits et al [12] and Van Hemelrijck et al [13] investigated the influence of parameters like the radius of the corner fillet and the thickness and the geometry of the biaxially loaded area by finite element simulations and experiments. This investigation led to a suitable specimen for fiber reinforced composite laminates with a reduced thickness area in the center region of the specimen, in combination with a fillet corner between arms.…”

Comparison of Different Techniques for Strain Monitoring of a Biaxially Loaded Cruciform Specimen

“…A consequence is that the tests will be performed in load‐control. More system specifications can be found in [12, 13].…”