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Analytical solutions for the deformation, penetration, and perforation of composite plates and sandwich panels subjected to quasi-static punch indentation and projectile impact are derived. Discrete spring-mass models are used to calculate the impact response of the composite plates and sandwich panels. Equivalent load resistance functions are obtained from the quasi-static analysis and adjusted for high strain rate. A generalized solution methodology for projectile impact of composite plates and sandwich panels are then proposed based on three key factors: (i) the contact load duration, (ii) the through-thickness transit time, and (iii) the lateral transit time. A two-dimensional wave propagation model is used to determine the ballistic limits of E-glass/polyester panels and GLARE fiber-metal laminates, and predicted values are found to be within 20 and 13% of the experimental results, respectively. A quasi-static impact model is used to predict the ballistic limit for E-glass/epoxy-aluminum honeycomb sandwich impacted by hemispherical nose projectile and the predicted values are within 11% of test results.

Analytical models for the static and low-velocity perforation of composite sandwich panel with woven E-glass/epoxy prepreg facesheets and aluminum honeycomb core are developed. The analytical models are based on a set of experimental results. A three-stage perforation process involving consecutive failures of top facesheet, core, and bottom facesheet is proposed. The analytical predictions of static failure loads and deformation are within 10 and 8% of the test data, respectively. The predicted ballistic limit is within 10% of the test data, while the total energy dissipated at the ballistic limit is within 18% of the test results.

Externally bonded glass fiber-reinforced polymer (GFRP) fabrics are being increasingly used for seismic retrofit and rehabilitation of concrete structures due to their high strength to weight ratio and low cost in comparison to carbon and aramid fibers. However, previous studies have shown that glass fibers are vulnerable to attack caused by harsh environmental weathering agents such as freezing—thawing, wetting—drying, and exposure to alkaline and acidic environments. Concerned with durability, this study is based on a fracture mechanics approach to evaluate the interface durability of GFRP bonded to normal concrete (NC) and high-performance concrete (HPC), subjected to two types of weathering protocols: (1) freeze—thaw cycling under calcium chloride, which is used to simulate the deleterious effect of the de-icing agents used on highways in wintry weather; and (2) alternate wetting and drying in a sodium-hydroxide solution, which is used to simulate the naturally occurring alkalinity due to the presence of concrete pore water, that can cause degradation due to a combination of mechanisms such as leaching and pitting of the glass fibers, and cracking and spalling of the resin matrix. Durability of the GFRP—concrete interface is characterized based on the critical strain energy release rate, under Mode-I loading, and weight and strain measurements. Unconditioned companion specimens are fractured alongside their aged counterparts to provide baseline-feedback and also enable comparative analysis of the fracture surfaces. Considerable degradation of the interface bond integrity is found to have resulted with increasing cycling period.

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