Establishing an unsteady fractional order Zener model with degradation parameters has significant meaning for predicting stress relaxation of fabric reinforced rubber composites. Based on the experimental results, an integer order Zener model was deduced to demonstrate the stress relaxation behaviors of fabric reinforced rubber composites and pure rubber. Due to the limitations, however, the integer order Zener model could not explain the stress relaxation behavior of the fabric reinforced rubber composites (the FRR) very well. Therefore, a Zener model was developed based on the viscoelasticity theory and the fractional calculus theory to characterize the stress relaxation behavior, but errors still existed in the initial and final stages. With more reasonable physical interpretation, an unsteady fractional order Zener model degraded by parametric aging with 7 parameters is proposed in this paper to accurately capture the stress relaxation behavior of the FRR, whose correlation coefficient is over 99.99%. The parameter sensitivities of the seven-parameter model were analyzed. Present study may provide a critical step for designing and evaluating the fabric reinforced rubber composites.

This study focuses on AG-80 epoxy resin, using 5228A and BA9916-II as representative examples. Saturated moisture absorption tests and dynamic mechanical analyses (DMA) were conducted to investigate its physical properties. The saturated moisture absorption rates and diffusion coefficients for 5228A and BA9916-II were measured. Their distinct molecular structures were found to lead to different moisture–absorption behaviors. A hygro-thermal–mechanical constitutive model for AG-80 resin (represented by 5228A) was developed, taking into account the effects of temperature and moisture content on mechanical properties. The model was validated by DMA tests on 5228A/CCF300 composites. The research findings of this study enhance the understanding of AG-80 epoxy resin and provide a theoretical basis for its application in high-temperature-resistant industrial environments.

To evaluate the energy absorption ability of composite beams with corrugated web under impact, the drop tests were conducted to demonstrate the fracture modes and obtain the load and energy history curves. Based on the drop tests, a finite element (FE) model was proposed with a weak link designed to trigger crushing, developed using Abaqus/Explicit, which integrates cohesive elements and employs the improved Hashin criterion along with the Choi–Chang criterion to accurately predict the onset and progression of delamination. The model accounts for the anisotropy and progressive damage in composite laminates. The periodic boundary conditions (PBCs) were integrated into the single-wave corrugated web beam model, the inherent limitations of which were corrected, enabling it to simulate the crushing process with the same effectiveness as the multi-wave model. As a result, the proposed model can accurately depict the progressive crushing behavior of corrugated web beams under impact loads while maintaining high computational efficiency.

Carbon fiber reinforced polymer (CFRP) is widely used in aircraft crashworthiness structures, but its unstable failure modes limit its energy absorption capability. This study proposes a hybrid aluminum/CFRP (Al/CFRP) corrugated web beam to enhance the energy absorption and progressive collapse under axial impact. Quasi-static crushing experiments were performed on CFRP and Al/CFRP corrugated web beams with 45° crushing triggers. Results revealed that the initial peak load and the total energy absorption of the Al/CFRP corrugated web beam increased by 16.68% and 34.62%, respectively, compared to those of the CFRP corrugated web beam. The specific energy absorption and the crushing force efficiency also improved by 13.22% and 1.51%, respectively. The CFRP corrugated web beam underwent transverse shearing, brittle fracture, and bending failures during crushing, resulting in a decline in energy absorption after a 40 mm displacement due to crack propagation. In contrast, the Al/CFRP corrugated web beam exhibited stable progressive collapse with sustained energy absorption up to a 60 mm displacement, benefiting from the plasticity of the aluminum layer. Detailed finite element models were validated against the experimental results, with the simulated failure morphologies and the energy absorption being consistent. The Al/CFRP corrugated web beam demonstrated superior crashworthiness, progressive collapse, and energy absorption capabilities under impact.