Fibre-reinforced polymer (FRP) composites generally have a layered architecture and are commonly manufactured with thermosetting resins—making them susceptible to interlaminar fracture (i.e. delamination), which is often a major concern in structurally critical applications. As a result, various approaches have been explored to enhance interlaminar fracture resistance. This review focuses on third-phase toughener inclusions, which offer opportunities to create damage resistant and damage tolerant structures without significantly adding weight or reducing in-plane mechanical properties. These toughener inclusions, typically introduced in the interlaminar regions, are divided into two categories herein: particle fillers and non-woven fibre veils. The advantages and limitations of both types are discussed, and the potential of the two approaches is evaluated using published data, aiming to provide an overview of the current understanding and challenges in designing and manufacturing safe and reliable composite structures.

In engineering industries, composite laminates have been widely applied for various applications. This work presents an efficient analysis of the interlaminar stresses in three-dimensional thin layered anisotropic composites by the boundary element method (BEM). Due to the nearly singular integrals in the boundary integral equation, the conventional BEM approach cannot be applied to analyze the composite layers that are very thin. The present work employs the self-regularization scheme to analyze the interlaminar stresses in thin anisotropic composites. In the end, a few benchmark examples are presented to show the applicability of the present approach.

Perforation process of a novel ceramic/composite panel including alumina-silicon carbide (Al2O3-SiC) nanocomposite as the front plate and ultra-high molecular weight polyethylene laminated composite (Dyneema® HB25) as the back-up impacted by a tip tapered penetrator has been analyzed based on LS-Dyna and HyperMesh codes. In order to balance the competing requirements posed by thickness, weight, cost and performance, a finite element (FE) simulation has been developed with well-developed material models. A two-dimensional, dynamic-explicit and Lagrangian model has been considered. The perforation process has been investigated for three different thicknesses of the ceramic plate. The Johnson-Cook, Johnson-Holmquist and Orthotropic-Elastic material models have been used for the penetrator, ceramic, and composite, respectively. The FE results, which have a good agreement with available experimental data, show that with the increase in the ceramic thickness, ceramic's fracture conoid as well as elasto-plastic deformation of fibers increase while fiber breakage and dishing of the composite layers diminish. In addition to saving cost and time, the FE simulation results can be useful as a fairly accurate prediction tool for the designing of lightweight body protective panels with desired impact resistance performance and eligible blunt trauma of the back-up.

Exact analysis of displacements and stresses in 2-D orthotopic laminates under extension is conducted. On the basis of the Hamiltonian state space approach and the transfer matrix method, a complete solution, in the context of generalized strain, which exactly satisfies the state space equation, the traction-free BC on the top and bottom surfaces of the rectangular section, the interfacial continuity conditions in multi-layered laminates, and the end conditions on free edges, is obtained by combing the eigensolutions and the particular solution. Evaluating of the stresses in the boundary layer for verification shows that the stress decay in laminates under uniform extension may be slow and the edge effects may be pronounced.

Based upon our recent development of Stroh-like forma lism for symmetric/unsymmetric laminates, most of the relations for bending problems can be organized into the forms of Stroh formalism for two-dimensional problems. Through the use of Stroh-like formalism, the fundamental elasticity matrices Ni, S, H and L appear frequently in the real form solutions of plate bending problems. Therefore, the determination of these matrices becomes important in the analysis of plate bending problems. In this paper, by following the approach for two-dimensional problems, we obtain the explicit expressions of the fundamental elasticity matrices for symmetric and unsymmetric laminates, which are all expressed in terms of the extensional, bending and coupling stiffnesses of the composite laminates.