Design Of Fiber Composites Research Articles

Strain- and stress-based parametric optimization of fiber-reinforced elastomers under finite deformations

In this work, a parametric optimization framework is developed to deal with fiber-reinforced elastomeric matrices. The fiber orientations are in a continuous set to obtain the set of angles that minimizes a functional given by the designer. Although this topic has been extensively studied in recent years, the vast majority of works use either gradient-based or global-based methods to define the composite fiber orientation, with the first being very prone to reach poor local minima and the latter increasing the computational burden exponentially with the number of design variables. Besides that, considering finite strain hyperelasticity, the number of works is substantially reduced. The main goal of this research is to study the efficiency of a local-based derivative-free algorithm in the optimization of problems considering finite deformation and material nonlinearity assumptions in fiber composite design. In order to show the proposed methodology efficiency, two optimization problems are studied: strain energy density minimization and mechanical stress minimization, with the latter further divided into a global and a cluster approach. Therefore, the main novelty of this work is to deal with fiber-reinforced elastomers optimization by means of a direct search algorithm in a constrained nonlinear optimization. The methodology can easily be implemented in existing finite element codes and the results show the pros and cons of both types of optimization.

Analysis of the Comprehensive Tensile Relationship in Electrospun Silk Fibroin/Polycaprolactone Nanofiber Membranes.

The mechanical properties of electrospun nanofiber membranes are critical for their applications. A clear understanding of the mechanical properties that result from the characteristics of the individual fiber and membrane microstructure is vital in the design of fiber composites. In this reported study, silk fibroin (SF)/polycaprolactone (PCL) composite nanofiber membranes were preparedusing an electrostatic spinning technology. The nanofiber orientation distribution (FOD) of the membrane was analyzed using multi-layer image fusion technology, and the results indicated the presence of an approximately uniform distribution of fibers in the electrospun membranes. The relationship between the single nanofiber and the membrane was established by analyzing the geometrical structure of the cell by employing a representative volume element (RVE) analysis method. The mechanical properties of the 272 nm diameter SF/PCL composite fibers were then predicted using the developed model.

High Volume Production Technology for Corrosive Resistant Long-Fiber-Reinforced Plastic Extinguishers

Portable fire extinguishers need to be reliable and fully functional at all given environmental conditions. Especially in off-shore and power plant applications a specific range of properties is necessary, e.g. corrosive resistance and electromagnetic compatibility. Hence, the application of fiber reinforced composites and fiber composite design offers an alternative to the traditional application of metallic materials.Within the scope of the development of an innovative fire extinguisher, a process-chain for manufacturing of composite fire extinguishers suitable for aggressively corrosive environmental conditions was developed. The aim of the project has been the development of a fire extinguisher with the technology of thermoplastic composite materials. Besides the intended weight reduction, a concept for the realization of a high-volume production suitable process-chain had to be developed. Using a thermoplastic matrix material allows a corrosive-free, non-magnetic and functional integrated design. Within the scope of the research project, the extinguisher container with integrated base and connection for the valve has been dimensioned and designed. The containers geometry with optimized ratio of filling volume, overall part size and material utilization was derived by applying FE analysis. Furthermore, a process-chain for high-volume production was conceived and had been verified by producing functional demonstrators for further testing.The container is made of two glass-fiber reinforced injection molding parts being thermally joined. The leakproofness and sufficient material strength after the joining process were identified as key challenges of the joining process and were overcome with an adapted design of the molded parts. Within the process development, reproducible and high quality weld joints were achieved based on a robust and cost-efficient joining technology. For reliable processing, the specific processing parameters were analyzed and regulations for each processing step deduced.

Estimating electrical conductivity of multi-scale composites with conductive nanoparticles using bidirectional time marching percolation network mapping

A computationally efficient approach is developed to determine electrical conductivity of large specimens of multi-scale composites composed of electrically conductive nanoparticles and nonconductive matrix and micro-scale reinforcements. As a test case, the paper studies nanocomposites and multi-scale fiber/polymer composites of carbon nanotubes. Fraction of percolating carbon nanotubes is defined as a metric for estimating electrical conductivity of composites with intermediate volume fraction of carbon nanotubes. The results indicate that for multi-scale composites with high fiber/reinforcement volume fraction, the simulation size needs to be in millimeters whereas for multi-scale composites with low fiber/reinforcement volume fraction, smaller simulation sizes (in 100s of microns) are sufficient. The present research is a first step towards efficient design of fiber composites for electromagnetic applications such as lightening protection and electromagnetic shielding.

Natural fiber composite design and characterization for limit stress prediction in multiaxial stress state

This paper focuses on the design of natural fiber composites and analysis of multiaxial stresses in relation to yield limit stresses of composites loaded off the fibers axis. ASTM D638-10 standard for tensile test was used to design and compose composites of plantain fiber reinforced polyester (PFRP). While the rule of mixtures was used in the evaluation of properties of composites in the fiber direction the evaluation of properties perpendicular or transverse to the fiber direction was done based on the value of the orthogonal stresses evaluated using ANSYS finite element software, the application of the Brintrup equation and Halpin–Tai equation. The yield strength for the plantain empty fruit bunch fiber reinforced polyester resin (PEFBFRP) was estimated as 33.69MPa while the yield strength of plantain pseudo stem fiber reinforced polyester resin (PPSFRP) was estimated as 29.24MPa. Above all, the PEFBFRP with average light absorbance peak of 45.47 was found to have better mechanical properties than the PPSFRP with average light absorbance peak of 45.77.

A code of practice for the structural design of fibre composites

The lack of appropriate structural design standards for composite materials is a major inhibitor to the wider usage of these materials in mainstream civil engineering. In 2000, the Composites Institute of Australia (CIA) moved to address this problem on a national level and initiated a programme to develop an Australian industry code of practice for the structural design of fibre composites. This paper discusses two of the initial topics addressed by this programme: the development of a national system of grading and certification for composite constituents, and an alternative approach to the characterisation of unidirectional lamina behaviour. The paper outlines the basis for investigation of each of these topics, and discusses the research approach that has been adopted. In the case of characterisation of lamina behaviour, the paper also presents initial results from associated experimental programmes.

A code of practice for the structural design of fibre composites

The lack of appropriate structural design standards for composite materials is a major inhibitor to the wider usage of these materials in mainstream civil engineering. In 2000, the Composites Institute of Australia (CIA) moved to address this problem on a national level and initiated a programme to develop an Australian industry code of practice for the structural design of fibre composites. This paper discusses two of the initial topics addressed by this programme: the development of a national system of grading and certification for composite constituents, and an alternative approach to the characterisation of unidirectional lamina behaviour. The paper outlines the basis for investigation of each of these topics, and discusses the research approach that has been adopted. In the case of characterisation of lamina behaviour, the paper also presents initial results from associated experimental programmes.

Microstructural design of fiber composites

Microstructural design of fiber composites

Microstructural design of fiber composites

The optimum performance design of composite microstructures is discussed. The forces driving progress in fiber composites are examined, and recent developments in the mechanics of laminated composites are surveyed, emphasizing thick laminates, hygrothermal effects, and thermal transient effects. The strength of continuous-fiber composites is discussed, presenting analyses of local load redistribution due to fiber breakages and treatments of statistical tensile strength theories. Modes of failure of laminated composites are examined. Elastic, physical, and viscoelastic properties as well as the strength and fracture behavior of short-fiber composites are studied, and it is shown how the performance of composites can be controlled by selecting material systems and their geometric distributions. 2D textile structural composites based on woven, knitted, and braided preforms are considered, and techniques for analyzing and modeling the thermomechanical behavior of 2D textile composites are presented. Recent developments in the processing of 3D textile preforms are introduced and the processing-microstructure relationship is demonstrated. Finite elastic deformation of flexible composites is addressed.

Designing for impact resistance with unidirectional fiber composites: Chamis, C. C., Hanson, M. P. and Serafini, T. T. National Aeronautics and Space Administration Technical Note D-6463, 41 pp (August 1971)

Impact resistant unidirectional fiber composite design based on micro and macromechanics, Izod impact tests, and residual stress and structural analyses