The impact resistance of composite materials — a review

The increasing complexity of engineering systems has sparked increasing interest in multidisciplinary optimization (MDO). This paper presents a survey of recent publications in the field of aerospace where interest in MDO has been particularly intense. The two main challenges of MDO are computational expense and organizational complexity. Accordingly the survey is focused on various ways different researchers use to deal with these challenges. The survey is organized by a breakdown of MDO into its conceptual components. Accordingly, the survey includes sections on Mathematical Modeling, Design- oriented Analysis, Approximation Concepts, Optimization Procedures, System Sensitivity, and Human Interface. With the authors'' main expertise being in the structures area, the bulk of the references focus on the interaction of the structures discipline with other disciplines. In particular, two sections at the end focus on two such interactions that have recently been pursued with a particular vigor: Simultaneous Optimization of Structures and Aerodynamics, and Simultaneous Optimization of Structures Combined With Active Control.

/pdf/multidisciplinary-aerospace-design-optimization-survey-of-3xuwvr970l.pdf

Multidisciplinary Aerospace Design Optimization: Survey of Recent Developments

The increasing complexity of engineering systems has sparked increasing interest in multidisciplinary optimization (MDO). This paper presents a survey of recent publications in the field of aerospace where interest in MDO has been particularly intense. The two main challenges of MDO are computational expense and organizational complexity. Accordingly the survey is focussed on various ways different researchers use to deal with these challenges. The survey is organized by a breakdown of MDO into its conceptual components. Accordingly, the survey includes sections on Mathematical Modeling, Design-oriented Analysis, Approximation Concepts, Optimization Procedures, System Sensitivity, and Human Interface. With the authors' main expertise being in the structures area, the bulk of the references focus on the interaction of the structures discipline with other disciplines. In particular, two sections at the end focus on two such interactions that have recently been pursued with a particular vigor: Simultaneous Optimization of Structures and Aerodynamics, and Simultaneous Optimization of Structures Combined With Active Control.

/pdf/multidisciplinary-aerospace-design-optimization-survey-of-ghzjxaiur6.pdf

Multidisciplinary aerospace design optimization: Survey of recent developments

Fibre-reinforced composites are rapidly gaining market share in structural applications, but further growth is limited by their lack of toughness. Fibre hybridisation is a promising strategy to toughen composite materials. By combining two or more fibre types, these hybrid composites offer a better balance in mechanical properties than non-hybrid composites. Predicting their mechanical properties is challenging due to the synergistic effects between both fibres. This review aims to explain basic mechanisms of these hybrid effects and describes the state-of-the-art models to predict them. An overview of the tensile, flexural, impact and fatigue properties of hybrid composites is presented to aid in optimal design of hybrid composites. Finally, some current trends in fibre hybridisation, such as pseudo-ductility, are described.

/pdf/fibre-hybridisation-in-polymer-composites-a-review-gcnp0ezsc7.pdf

Fibre hybridisation in polymer composites: a review

Meso-FE modelling of textile composites: Road map, data flow and algorithms

Composite mechanics disciplines are presented and described at their various levels of sophistication and attendant scales of application. Correlation with experimental data is used as the prime discriminator between alternative methods and level of sophistication. Major emphasis is placed on (1) where composite mechanics has been; (2) what it has accomplished; (3) where it is headed, based on present research activities; and (4) at the risk of being presumptuous, where it should be headed. The discussion is developed using selected, but typical, examples of each composite mechanics discipline identifying degree of success, with respect to correlation with experimental data, and problems remaining. The discussion is centered about fiber/resin composites drawn mainly from the author's research activities and experience spanning two decades at National Aeronautics and Space Administration (NASA) Lewis Research Center.

/pdf/mechanics-of-composite-materials-past-present-and-future-4pbfzisthb.pdf

Mechanics of Composite Materials: Past, Present, and Future

: A two-level, linear, semiempirical theory for a failure criterion in described. The theory predicate the strength behavior of undirectional filamentary composites under uniaxial and combined stress from basic constituent material properties and fabrication process considerations. Applications of the theory to several filament-non-metallic matrix composite, are presented and comparisons are made with experimental data. These results show good agreement between theory and experiment. Simple and combined strength envelopes are generated to illustrate the versatility of the theory and to point out problem areas in experimental work and design. (An)

/pdf/failure-criteria-for-filamentary-composites-13sqahn6b4.pdf

Failure Criteria for Filamentary Composites

A methodology is developed to computationally assess the probabilistic composite behavior at all composite scales (from micro to structural) due to the uncertainties in the constituent (fiber and matrix) properties, in the fabrication process and in structural variables (primitive variables). The methodology is computationally efficient for simulating the probability distributions of composite behavior, such as material properties, laminate and structural responses. Byproducts of the methodology are probabilistic sensitivities of the composite primitive variables. The methodology has been implemented into the computer codes: Probabilistic Integrated Composite ANalyzer (PICAN) and Integrated Probabilistic Assessment of Composite Structures (IPACS). The accuracy and efficiency of this methodology are demonstrated by simulating the uncertainties in composite typical laminates and comparing the results with the Monte Carlo simulation method. Available experimental data of composite laminate behavior at all scales fall within the scatters predicted by PICAN. Multi-scaling is extended to simulate probabilistic thermo-mechanical fatigue and to simulate the probabilistic design of a composite redome in order to illustrate its versatility. Results show that probabilistic fatigue can be simulated for different temperature amplitudes and for different cyclic stress magnitudes. Results also show that laminate configurations can be selected to increase the redome reliability by several orders of magnitude without increasing the laminate thickness––a unique feature of structural composites.

Probabilistic Simulation of Multi-Scale Composite Behavior

A methodology is developed to computationally assess the non-deterministic composite response at all composite scales (from micro to structural) due to the uncertainties in the constituent (fiber and matrix) properties, in the fabrication process and in structural variables (primitive variables). The methodology is computationally efficient for simulating the probability distributions of composite behavior, such as material properties, laminate and structural responses. Bi-products of the methodology are probabilistic sensitivities of the composite primitive variables. The methodology has been implemented into the computer codes PICAN (Probabilistic Integrated Composite ANalyzer) and IPACS (Integrated Probabilistic Assessment of Composite Structures). The accuracy and efficiency of this methodology are demonstrated by simulating the uncertainties in composite typical laminates and comparing the results with the Monte Carlo simulation method. Available experimental data of composite laminate behavior at all scales fall within the scatters predicted by PICAN. Multi-scaling is extended to simulate probabilistic thermo-mechanical fatigue and to simulate the probabilistic design of a composite redome in order to illustrate its versatility. Results show that probabilistic fatigue can be simulated for different temperature amplitudes and for different cyclic stress magnitudes. Results also show that laminate configurations can be selected to increase the redome reliability by several orders of magnitude without increasing the laminate thickness--a unique feature of structural composites. The old reference denotes that nothing fundamental has been done since that time.

/pdf/probabilistic-simulation-of-multi-scale-composite-behavior-3yevhjftdx.pdf

The invention relates to laminate structures and specifically to essentially anisotropic fiber composite laminates wherein metal foils are selectively disposed within the laminate to produce increased resistance to high velocity impact, fracture, surface erosion, and other stresses within the laminate.

/pdf/hybrid-composite-laminate-structures-5g1gcjwtpi.pdf

Christos C. Chamis

Papers

Mechanics of Composite Materials: Past, Present, and Future

Failure Criteria for Filamentary Composites

Probabilistic Simulation of Multi-Scale Composite Behavior

Probabilistic Simulation of Multi-Scale Composite Behavior

Hybrid composite laminate structures