A Monte Carlo simulation is developed to provide a foundation for interpreting experimental data from the single-filament-composite test. The main focus is on developing an improved procedure for arriving at a realistic value for the shear strength of the fiber-matrix interface, but it is also shown how the test may be used to characterize the strength distribution of fibers at a length scale much shorter than is achievable in standard tension tests. The simulation is based on the widely used Poisson/Weibull probability model for fiber failure that characterizes the strength in terms of the random flaws distributed along the fiber. The primary mechanical model for stress buildup at the fiber end is the same as that assumed by most authors and assumes a constant interfacial shear stress in this shear transfer zone reminiscent of a yielding plastic matrix. We also, however, consider a bilinear model that allows for a zone of debonding with a constant shear stress lower than in the primary “plastic” zone. Simulation results are cast in terms of nondimensional variables and tabulated to allow for wide applicability. Sample size and confidence interval issues are also discussed.

Interfacial shear strength studies using the single-filament-composite test. Part II: A probability model and Monte Carlo simulation

Life-cycle reliability-based optimization of civil and aerospace structures

Today, it is widely recognized that optimization methodologies should account for the stochastic nature of engineering systems and that concepts and methods of life-cycle engineering should be used to obtain a cost-effective design during a specified time horizon. The recent developments in life-cycle engineering of civil and aerospace structures based on system reliability, time-dependent reliability, life-cycle maintenance, life-cycle cost and optimization constitute an important progress. The objective of this study is to present a brief review of the life-cycle reliability-based optimization field with emphasis on civil and aerospace structures. � 2003 Published by Elsevier Science Ltd.

Review Article Life-cycle reliability-based optimization of civil and aerospace structures

The strength of high-performance filaments is a complex parameter which can not be fully described with a single value. The Weibull model is used to describe the intrinsic statistical nature of the fracture strength. Possibilities and limitations of the Weibull model are illustrated. The relationship between material properties and the parameters in the Weibull model is discussed.

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The Concept of Filament Strength and the Weibull Modulus

1.19 – Statistical Strength Theory for Fibrous Composite Materials

A probabilistic model for the tensile strength of brittle fibers is presented and related to present conventional testing The relationship of fiber flaw structure to the statistical strength is dis...

Clamp Effects in Fiber Testing

A probabilistic optimum design approach is presented with minimum expected cost as the design objective. Statically determinate trusses are used to demonstrate the approach. The minimization of expected cost is shown to be equivalent to minimum weight with a probability of failure constraint. Sensitivity studies of safety index, cost of failure, and material and load parameters are presented. A simple design aid is included for the expected cost optimization of statically determinate trusses with random strength and deterministic load.

Robert G. Sexsmith

Papers

Clamp Effects in Fiber Testing

Minimum Expected Cost Optimization