Residual Strength Of Composites Research Articles

Determination of residual strength in notched APC-2 cross-ply composite laminates at elevated temperature

The residual strength of notched AS-4/polyetheretherketone (PEEK) composite (APC-2) laminates with a central hole at elevated temperature was systematically investigated by both analytical and empirical methods. First, APC-2 cross-ply [0/90]4s panels were fabricated and cut into samples. A circular hole with one of five diameters was drilled in the center of each sample. The samples were subjected to quasi-static tensile tests at elevated temperatures to measure their mechanical properties – strength and longitudinal stiffness. Stress concentration and high temperature were found to remarkably affect the residual strength of composite. Point stress criterion (PSC) above was found to be unsatisfactory in predicting the residual strength. A modified PSC combined with the equation of thermal degradation was able to predict the characteristic length at elevated temperature. The residual strengths predicted by the extended modified PSC model were in very close agreement with the empirical data.

Non-destructive evaluation of erosion damage on E-glass/epoxy composites

Abstract A non-destructive evaluation method for predicting the residual tensile strength of erosion damaged fiber-reinforced composites was developed based on monitoring the acoustic emission (AE) activity of the composite specimens during uniaxial tensile loading. The developed method was used for estimating the residual strength of E-glass/epoxy composite with ply sequence of [45°/−45°/0°/45°/−45°/0°] S . A mixture of air and SiC particles with diameter of 400–500 μm was blasted to the composite specimens at various impact angles and durations to induce the local damage. Subsequently, uniaxial tensile tests were carried out on the specimens subjected to solid particle erosion as well as undamaged specimens while monitoring the acoustic emission activity. The extent and mechanisms of damage due to tensile loading of composite specimens were explored by examining the failure surface upon completion of tensile tests under a scanning electron microscope (SEM) and by measuring the distribution of AE events by event duration, ring down counts and energy distribution during tensile tests. Weibull probability distribution model and AE stress delay parameter model were developed to relate the AE activity to the erosion damage and residual strength. The results show that the developed non-destructive method is capable of predicting the residual strength of composites subjected to solid particle damage.

Residual strength of composites with multiple impact damage

In recent years attention has focused on damage interaction, with particular emphasis on multi-site damage. Whilst most attention has focused on fuselage lap joints, related problems occur in composite structures which are subjected to multiple impact damage. This paper reveals that for composites there is little interaction between damaged regions, provided they are separated by more than one diameter. This methodology was verified via a coupon test program and an experimental evaluation of two damaged F/A-18 horizontal stabilators.

Effect of low-velocity impact on the residual strength of composites

Effect of low-velocity impact on the residual strength of composites