In this study, the impact behaviors of laminated and sandwich hybrid composites produced with two different methods with the same fiber and wire mesh arrangements were investigated. The samples produced in the study were obtained by using 0.5 mm and 1 mm thick metal wire mesh together with carbon fiber reinforced polymer (CFRP) composite. Low-velocity impact tests were applied to four different hybrid composite samples for both manufacturing methods without wire mesh, with wire mesh having a diameter of 0.5 mm, 1 mm and both 0.5 mm and 1 mm at 30 J and 90 J energy levels. According to the data obtained, the samples were not perforated at the energy level of 30 J, but damaged. Composites with 0.5 mm and 1 mm metal wire mesh made a positive contribution to CFRP composites in terms of rebound energy. At the energy level of 90 J, samples with wire mesh having a diameter of 1 mm and, both 0.5 mm and 1 mm were not perforated, while the others were perforated. The highest reaction force was obtained in sandwich samples with both 0.5 mm and 1 mm wire meshes at the 90 J energy level. Due to bonding and increasing thickness, reaction force in sandwich sample S_05_1 was 36% higher than the laminated composite with the same arrangement, L_05_1.
This study examines the tensile behavior of carbon/glass hybrid composite laminates fabricated via vacuum-assisted resin transfer molding (VARTM). Three symmetric hybrid laminates comprising six glass (G) plies and four carbon (C) plies were produced: two “grouped” lay-ups, [G₃C₂]s (H1) and [C₂G₃]s (H2), and one “dispersed” lay-up, [GCGCG]s (H3), in addition to the baseline 10-ply carbon [C10] and 10-ply glass [G10] laminates. An MTS servo-hydraulic testing machine was utilized for the tensile experiments, and strain measurements were obtained via digital image correlation (DIC), while in-situ high-speed camera (HSC) imaging was employed to capture the failure sequence during fracture. The results indicate that the H1 configuration, with glass plies placed on the outer faces, exhibits the highest tensile strength with an increase of 42% compared to the G10 laminate, and failure strain with an enhancement of 33% with respect to the C10 laminate. The HSC observations further reveal that ply arrangement governs the damage evolution: grouped hybrid laminates fail through carbon fiber fracture followed by extensive interfacial delamination, whereas the dispersed laminate exhibits predominantly fiber-dominated failure with minimal delamination. These findings provide direct experimental evidence of the influence of ply dispersion on the failure mechanism of carbon/glass hybrid laminates.
Understanding the snap-back behaviour exhibited by class-II brittle rocks is of importance, as it indicates an energy imbalance that leads to extreme dynamic responses. The test control method influences the fracturing behaviour, thus the obtained strength and fracture energy. Therefore, it is essential to understand the influence of the control methods on the tensile and fracture behaviour of rocks for a more accurate evaluation of fracture properties. In this study, conventional Brazilian disc tests (BD) were carried out on sandstone specimens, along with snap-back control based on the AUSBIT (Advanced Universal Snap-Back Indirect Tensile) testing method. AUSBIT utilises an indirect control approach to stabilise the fracturing process, thereby enabling the capture of snap-back behaviour. This allows for minimising dynamic effects to accurately obtain better intrinsic properties. The experimental results reveal significant variations in tensile strength measured using the AUSBIT method compared to the BD testing. This highlights the effectiveness of AUSBIT and offers important insights into rock fracture behaviour, supporting the potential of AUSBIT as a valuable tool for studying fracturing behaviour in brittle materials.
Bird strikes can threaten the integrity of PMMA aircraft transparencies, creating a need for accurate and efficient impact-assessment tools. This study presents an experimental–numerical framework supported by machine learning. The viscoelastic response of PMMA is represented using a Generalized Maxwell model, with Prony-series parameters identified from stress relaxation tests. The finite element model is first validated against steel ball impact experiments, yielding residual-velocity errors below 3%. It is then evaluated against three gelatin bird-strike experiments modeled using Smoothed Particle Hydrodynamics (SPH), reproducing the observed intact and fractured plate responses. A simulation-generated dataset spanning projectile velocity, plate thickness, and mesh density is used to train Random Forest and Gradient Boosted Regression Tree (GBRT) surrogate models for predicting the residual velocity of the steel projectile. The GBRT model outperforms Random Forest, achieving an R2 of 0.999 and an RMSE of 0.563 m/s on the validation dataset. These results show the potential of combining experimentally calibrated viscoelastic modeling with machine learning for PMMA impact assessment.
Single-factor ultrasonic rolling experiments were conducted to investigate the evolution of residual stress and hardness in 42CrMo steel under different processing conditions. The distributions of residual stress and hardness along the depth direction were analyzed under varying static pressures and ultrasonic amplitudes. The results indicate that ultrasonic rolling introduces a compressive residual stress layer beneath the treated surface. As the depth increases, the compressive residual stress initially rises to a maximum value and subsequently decreases gradually, eventually approaching the stress state of the substrate. In addition, ultrasonic rolling promotes plastic deformation in the near-surface region, resulting in the formation of a hardened layer with higher surface hardness compared with the untreated material. Increasing static pressure and ultrasonic amplitude contributed to higher compressive residual stress and greater surface hardening. These changes in surface integrity may be beneficial for improving the mechanical performance of 42CrMo steel components.
