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a b s t r a c t a r t i c l e i n f o Keywords:Composite materials Sandwich Multiplate structure Impact behaviour Aerospace materialsIn this paper the ballistic behaviour of several glass/polyester laminate structures was studied, evaluating the residual velocity of the projectile and the damage area. Three monolithic laminates of different thicknesses and two multiplate laminate structures were analyzed: one of a sandwich type with face sheets of glass/ polyester and a foam core, and another made with the same face sheet, which were separated by a distance equal to the thickness of the core. It was found that laminates of greater thickness show a larger damage area and a greater ballistic limit. The influence of the core on the ballistic limit of multiplate laminate structures is negligible but, nevertheless, the extension of the damage area in the back face sheet is increased.

In this work, the effect of a biaxial preload in the behaviour of glass/polyester woven laminate plates subjected to high velocity trans versal impact was studied. For this, an analytic model based on energy considerations that include the presence of an in plane preload was used. The results of the analytic model for the biaxial preload state were compared with those found for a non preload plate, the difference between them being minimal for the pre stressed level reached in the tests (31% of the static UTS). Therefore, numerical simulations were made in order to study the effect of the preload in greater detail; furthermore, experimental tests were conducted, validating the analytic and numerical model. In general, the two methods revealed minimal differences between the values of the ballistic limit and those of the residual velocity.

Damage evolution of notched composite laminates is analysed in this work using a discrete damage model, which estimates matrix damage evolution and fibre failure. The fibre damage is regularized with a Weibull distribution, and a Regula Falsi method has been used to improve numerical convergence. The model is compared and validated with several experimental results taken from the scientific literature, which consider different materials, laminate stacking sequences and specimen geometries. A good correlation has been found for the failure strength and the stress-strain curve of notched and un-notched laminates subjected to in plane loads. The influence of the Weibull modulus on the matrix and fibre damage evolution, and the failure strength, is analysed.

This is a postprint version of the following published document:Iváñez, I.; Moure, M. M.; García-Castillo, S. K.; Sánchez-Sáez, S. (2015). The oblique impact response of composite sandwich plates.

Adhesively bonded joints are widely used in structures manufactured with composite laminates. Single-lap adhesive joints are the common most used due to their simple geometry and structural efficiency. In this study, a 2D numerical model has been developed in Abaqus/Standard to evaluate the influence of variations in the geometry of the adherends and the adhesive on the mechanical strength of a single-lap joint subjected to uniaxial tensile load, using the Cohesive Zone Model (CZM). Different geometrical configurations of single-lap joints have been studied, such as adherend recessing and chamfering of the adherends and adhesive. The objective is to analyse the effect of these variations with respect to the mechanical strength of the adhesive joint. In this sense, the vertical displacement of the adherends, the peak peel stress, the distribution of peel stress on the overlap length, and the failure load have been studied, identifying the chamfer in the adherends and adhesive as the most influential parameter governing the strength of the adhesive joint.

This work evaluates the behavior of sandwich and spaced plates subjected to high-velocity impacts. The sandwich structures were made of glass/polyester face-sheet and a PVC foam core. The spaced plates were made of two plates of the same material of the sandwich face-sheet at a distance equal to the core thickness. The residual velocity, the ballistic limit, and the damage area were selected to compare the response of both structures. The residual velocity and ballistic limit was very similar in both cases. Nevertheless, the damage area of sandwich structures and spaced plates differed due to the dissimilar properties between the sandwich core and the air inside of the spaced plates. An analytical model, based on energy criteria, was applied to estimate the residual velocity of the projectile, the absorbed energy by each facesheet, and the ballistic limit in the spaced plates. PO-LYM. COMPOS., 00:000-000,

Abstract. An experimental and analytical study of two cases of static preload (uniaxial and biaxial) was made to detennine the response of structural plate elements subjected to high velocity impacts under inplane tensile preloading conditions. The results were compared with those obtained in non-preloading specimens. Rectangular specimens were used for the uniaxial and non-preload tests, while cross-shaped specimens were used for the biaxial tests. The impacts were made by spherical projectiles travelling at velocities from 140 to 525 m/s. As a general result, the existence of a static preloading on the specimen was found to affect the ballistic limit and the damaged area. The biaxial preload specimens showed the higher ballistic limit and the damaged area was slightly bigger in the non-preloaded specimens. From the analytical model, the ballistic limit calculated for the non-loaded specimens showed a difference of 16% from the experimental values, and in the preloaded specimens the model did not show showed the same tendency as that observed experimentally.