Dispersion of Mechanical Properties of High-Strength Glass Fibre Composites in Hygrothermal Environment.

High-strength glass fibre-reinforced composites (H-GFRPs) are widely used in various engineering fields because of their excellent mechanical properties and designability. The mechanical properties of H-GFRPs are more sensitive to temperature and humidity. Under high temperature and humidity conditions, the properties decrease greatly and the dispersion increases. Tensile, compressive, and in-plane shear tests were carried out on five batches of H-GFRPs under five different conditions, and the strength and stiffness properties under different test conditions were obtained. In this paper, the strength and stiffness properties of H-GFRPs under room temperature and hygrothermal conditions are statistically analysed based on macroscopic test data and the meso-bridging model. The results showed that under hygrothermal conditions, the dispersion of performance tended to decrease. The distribution types of other parameters are consistent with those under room temperature conditions, except for the transverse tensile modulus E22,t and longitudinal compressive strength Xc, which tend to follow a normal distribution. Among the four stiffness performance parameters, the correlation between v12 and the other three stiffness parameters was weak, whereas that between the other three stiffness parameters was strong.

High-Temperature Compressive Response of SiCp/6092Al Composites under a Wide Range of Strain Rates.

The high-temperature dynamic compressive properties of a 30 vol.% SiCp/6092Al composite, fabricated using powder metallurgy, were experimentally investigated using the split Hopkinson pressure bar system with an electric furnace. Three different ambient temperatures, namely, room temperature, 200 °C, and 350 °C, were adopted, and the dynamic tests of the composite specimens were conducted at strain rates ranging from 1500 to 4500 s-1. The experimental results showed that the flow stress of the composite was generally insensitive to strain rates at room temperature. However, the composite started exhibiting different strain-rate-dependent behaviors as the temperature increased, and the flow stress nonlinearly varied with increasing temperature. In addition, the microscopic images of the specimens showed that the microscopic failure mechanisms of the composite were greatly influenced by the ambient temperature and strain rate. Specifically, the percentage of failed particles decreased with rising temperature and the dominating failure mode of particles changed significantly as the strain rate increased.

A Reliable Fracture Angle Determination Algorithm for Extended Puck's 3D Inter-Fiber Failure Criterion for Unidirectional Composites.

Determination of the fracture angle and maximum exposure value of extended Puck's 3D inter-fiber failure (IFF) criterion is of great importance for predicting the failure mechanism of unidirectional fiber-reinforced composites. In this paper, a reliable semi-analytical algorithm (RSAA) is presented for searching fracture angle and corresponding exposure value for the extended Puck's failure criterion. One hundred million cases are tested for verifying the accuracy of the present and other algorithms on Python using the strength-value-stress-state combinations more universal than those in previous literatures. The reliability of previous algorithms is discussed and counterexamples are provided for illustration. The statistical results show RSAA is adequate for implementation in extended Puck's criterion and much more reliable than previous algorithms. RSAA can correctly predict the results with a probability of over 99.999%.

Multiscale Analysis of Mechanical Properties of 3D Orthogonal Woven Composites with Randomly Distributed Voids.

Voids are common defects in 3D woven composites because of the complicated manufacturing processes of the composites. In this study, a micro-meso multiscale analysis was conducted to evaluate the influence of voids on the mechanical properties of three-dimensional orthogonal woven composites. Statistical analysis was implemented to calculate the outputs of models under the different scales. A method is proposed to generate the reasonable mechanical properties of the microscale models considering randomly distributed voids and fiber filaments. The distributions of the generated properties agree well with the calculated results. These properties were utilized as inputs for the mesoscale models, in which void defects were also considered. The effects of these defects were calculated and investigated. The results indicate that tensile and shear strengths were more sensitive to the microscale voids, while the compressive strength was more influenced by mesoscale voids. The results of this study can provide a design basis for evaluating the quality of 3D woven composites with void defects.