Reliability Of Composite Materials Research Articles

A Review of Delamination Damage of Composite Materials

The theoretical and practical achievements in the field of the theory of strength and reliability of composite materials are discussed in a review conducted on the scientific research conducted on the effect of delamination on the reliability and quality of composites. The methodological aspects of the stability of the mechanical characteristics of composite materials under the combined action of cyclic and impact loads are examined, as are the manufacturing and processing technologies. The reasons for delamination, such as technological, manufacturing and application, free edge, joints and loads, are revealed. The influence of delamination on the bearing capacity of structural elements made of composite materials is analyzed. The mechanism of delamination growth is outlined, and the criteria and processes are defined, such as the growth of delamination cracks in a multidirectional laminated plate from a straight edge, edge delamination during plate bending, delamination in plates in the field of residual stresses, etc. The importance of taking into account the visco-plastic effect at the top of the edge crack of delamination of composite materials is emphasized. The concept of critical delamination behavior is characterized, and the issues of delamination stability are described.

Development and application of combined methods to expand the potential for predicting the defining characteristics of composites

The issue of promising ways to expand potential opportunities for improving the effectiveness of methods for predicting the remaining life, durability, and reliability of composite materials and structures under the influence of extreme environmental factors is considered. Modifications of methods for searching for the global extremum of multiparametric functions have been developed and studied, taking into account the structural peculiarities of the efficiency criteria used in forecasting the remaining life and durability of structures made of composite and polymer materials. One of the promising ways to increase the potential opportunities has been analyzed. It is connected with the improvement of methods for constructing optimal directions for searching for the absolute minimum of efficiency indicators related to solving the problems of predicting the determining characteristics of polymer composites under the influence of extreme environmental factors and operational loads.

Statistical prediction of the reliability of composite materials with dispersive inclusions

An algorithm for the reliability (probability of failure) calculating of composite materials with stochastically distributed dispersive inclusions under conditions of a complex stress state is proposed. The deterministic composite failure criterion of a Coulomb friction with clutch type is considered. The distribution function of the composite failure loading is obtained, which is the basis for writing the statistical characteristics of materials strength and reliability. The diagrams of the applied loading dependence on the probability of failure of a flat composite sample with different structural heterogeneity of the material and numbers of inclusions are calculated and constructed

A novel predictive model for mechanical behavior of single-lap GFRP composite bolted joint under static and dynamic loading

Mechanical connection of composite is critical due to its complicated meso-structure and failure mode, which has become a bottleneck on reliability of composite material and structure. Although many researches on composite bolted joints have been carried out, the theory and experiment on mechanical behavior of such a joint structure under dynamic loading were rarely reported. Here, we propose a novel predictive model for quasi-static and dynamic stiffness of composite bolted joint by introducing the strain rate dependent elastic modulus into the mass spring model. Combined with the composite laminate theory and Tsai-Hill theory, the present model was capable of predicting the strain rate dependent stiffness and strength of the composite bolted joint. Quasi-static and impact loading experiments were carried out by Zwick universal hydraulic testing machine and split Hopkinson tension bar, respectively. The stiffness and strength predicted by our model showed good accordance with the experiment data with errors below 12% under quasi-static loading and below 30% under impact loading. The results indicated that under impact loading, stiffness and strength of the composite bolted joint were significantly higher than their quasi-static counterparts, while the failure mode of the joint structure trended towards localization which was mainly bearing failure. Among various lay-up ratios studied, the optimal lay-up ratio for quasi-static and dynamic stiffness was 0:±45:90 = 3:1:1.

Reliability in composites – A selective review and survey of current development

As a response to the rampant increase in research activity within reliability in the past few decades, and to the lack of a conclusive framework for composite applications, this article attempts to identify the most relevant reliability topics to composite materials and provide a selective review. Available reliability assessment methods are briefly explained, referenced and compared within an unified formulation. Recent developments to confer efficiency in computing reliability in large composite structures are also highlighted. Finally, some general conclusions are derived along with an overview of future directions of research within reliability of composite materials and their influence on design and optimization.

Failure Analysis on Rubber-Modified Epoxy Resin under Various Loading Speed Conditions

A rubber-modified epoxy resin is widely used as adhesive and matrix materials for fiber composite material. The structural reliability of composite material depends on the fracture toughness of the matrix resin. In this study, the fracture toughness and the damage zone around a crack tip in rubber-modified epoxy resin were investigated. The volume fractures of rubber (CTBN1300×8) in the rubber-modified epoxy resin were 0%, 5% and 15% under several loading speeds. The fracture toughness(KIC) and the fracture energy(GIC) were measured by using 3-point bending specimens. The 4-point bending specimens were also used to observe damage zones at the vicinity of a crack tip in modified resins. The results show that the values of the fracture toughness and the sizes of damage zones at 5% and 15% rubber content decrease with increase in loading speed.

Reliability of Composite Materials under General Plane Loadings

The reliability method of design is one in which we learn or determine the statistical distributions of stresses and strengths, and then relate these two in order to achieve an acceptable success rate. In this article, a methodology is introduced to study the reliability of composite materials in an attempt to improve consistency in the treatment of uncertainty of both loadings and material properties. Micro-mechanical analysis is utilized to represent the effects of statistical distributions of micro-parameters on global failure. The analysis is combined with the Tsai-Hill failure criterion and models of structural reliability to study the reliability optimization and the influence of micro-level material pa rameters on reliability of composites.

Thermodynamic Criteria for the Maximum and Minimum Strength of Fibre-Reinforced Composite Materials

Abstract The overall performance and reliability of composite materials are, in most cases, dependent upon the behaviour of the reinforcement-matrix interface, particularly upon its ability to transfer stress. A theory for predicting thermodynamic conditions for the maximum and zero-adhesion at the reinforcement-matrix interface is tested in this paper, based on experimental data. Proposed is a model of the relationship between mechanical properties of composite materials (tensile strength, flexural strength, Young's modulus and impact resistance) and energetic properties of matrix and reinforcement expressed by the energy ratio a = γ l/γ2.

The Effect of Stress Concentration on the Reliability of Composite Materials

A model is presented for predicting reliability of brittle composite structures with complex multiaxial stress states. This model allows all of the stress components to con tribute to the probability of material fracture. The model is applied to an off-axis geometry and to a center through-hole off-axis geometry using several different material systems. Results for the off-axis geometry demonstrate the importance of using the correct specimen configuration when performing a reliability analysis. Stresses induced by the end-constraint may cause an over prediction of reliability or an underutilization of material strength, depending on the overall stiffness and strength characteristics of the material. Results for the center-notched off-axis geometry demonstrate the effect of strength variability on the localization of fracture prob ability. Low variability materials exhibit a localization of high probability of failure regions, implying a high repeatability of fracture initiation site. High variability materials exhibit a smoothing of the high failure probability regions, which denotes less sensitivity to the stress concentration. Regions which contribute heavily to a loss in structure reliability may be identified before testing, so that a redesign may be effected.