Progressive Crushing of Polymer Matrix Composite Tubular Structures: Review

The present paper reviews crushing process of fibre-reinforced polymer (FRPs) composites tubular structures. Working with anisotropic material requires consideration of specific parameter definition in order to tailor a well-engineered composite structure. These parameters include geometry design, strain rate sensitivity, material properties, laminate design, interlaminar fracture toughness and off-axis loading conditions which are reviewed in this paper to create a comprehensive data base for researchers, engineers and scientists in the field. Each of these parameters influences the structural integrity and progressive crushing behaviour. In this extensive review each of these parameters is introduced, explained and evaluated. Construction of a well-engineered composite structure and triggering mechanism to strain rate sensitivity and testing conditions followed by failure mechanisms are extensively reviewed. Furthermore, this paper has mainly focused on experimental analysis that has been carried out on different types of FRP composites in the past two decades

Analysis of the effect of impact damage on the repairability of composite panels

The present paper aims to provide further understanding of the behaviour of Carbon Fibre Reinforced Plastic (CFRP) composite panels under high velocity impact and develop design guideline for repair of damaged composite panels in order to increase the aircraft survivability. This work consists of two parts: part one is a combination of experimental investigation and numerical simulation to evaluate the impact of a woven CFRP laminate which were subjected to selected impact velocities (100 m/s–500 m/s) in order to evaluate the induced impact damage in two different thicknesses of CFRP composite panels (4.125 mm and 2.625 mm). In part two a finite element model is developed to design a guideline for repairing of a composite panel. In order to achieve this an optimised repair models with variable parameters such as number of steps and length of steps in the stepped lap joints are investigated. The penetration process and also change of kinetic energy absorption characteristics have been used to validate the finite element results. Finite element results were in close agreement with experimental data obtained from different sources

Effect of multi stitched locations on high speed crushing of composite tubular structures

The present paper experimentally investigates progressive energy absorption of fibre-reinforced polymer (FRP) composite tubular structures under high speed loading conditions. Various multi stitched locations are studied to find a correlation between single and multi-locations of stitches and energy absorption capabilities of composite absorbers. The through-thickness reinforcements are applied into locations of 10 mm, 20 mm, 30 mm, 10–20 m, 10–30 mm, 20–30 mm, 10–20–30 mm and 10–15–20–25–30–35 mm from top of the tubes. It is shown that multi-stitched location can cause several increase of crushing load and consequently increase of energy absorption of composite tube absorbers. The idea would be expanded to other designs which are followed by increase of stitched locations and reduction of the distance between stitches to improve the mean force with a smooth and progressive pattern of crushing load

Post impact analysis of damaged variable-stiffness curved composite plates

This research studies the post impact response of damaged area of variable stiffness curved composite plates. Varying thicknesses of sections is widely found in aerospace and automotive composite sub structures. In this regard, the impact response of this geometry characteristic has to be studied in thin-walled structures. In our model, a removal of ply technique is used to represent damaged region within a curved panel, thus degrading the stiffness in that area is considered in the theoretical models. A summation of spring-mass systems is used in the modelling of damaged variable stiffness plate to analysis post impact behaviour of these structures. The theoretical force-time results are also compared with the relevant finite element outcomes in LSDYNA. The comparison establishes a good prediction capability of the proposed model

Cohesive zone modeling (CZM) in prediction of delamination failure in laminated composite structures

The ply delamination which is known as a principle mode of failure of layered composites due to separation along the interfaces of the layers is one of the main concerns in designing of composite material structures. In this paper first the double cantilever beam (DCB) and three-point-end-notched flexure (3ENF) specimens were fabricated from carbon/epoxy twill-weave fabrics and they were tested under quasi-static condition to determine the interlaminar fracture toughness in Mode-I (GIC) and Mode-II (GIIC) of the selected lay-up. The cohesive zone modeling (CZM) which is known as a variation in the cohesive stresses with the interfacial opening displacement along the localized fracture process zone was used in ANSYS to predict the Mode-I and Mode-II delamination failure in laminated composite structures. The numerical results were verified with the relevant experimental results

Avoid catastrophic failure in wind turbine blades: a study of delamination under various loading conditions

Wind turbine blades are typically manufactured from fibre-reinforced polymer (FRP) composites, and delamination failure can be an important issue in these structures. In extreme conditions, such as ice impacting, multiple delamination with a triangular shape is found in different parts of a blade. This delamination introduces local damage, which can then cause catastrophic failure under various loading conditions including buckling. Buckling and post-buckling are two loading conditions that can occur in large wind turbine blades due to gravitational, aerodynamic and centrifugal forces. In the work reported here, experimental studies of buckling and post-buckling failure in multi-delaminated composite beams were carried out. Laminated composite beams were pinned through their thickness using natural flax yarns to control delamination failure during the post-buckling process. Multi-delaminated composite beams were manufactured with laminate designs of [C90/G90]4 and [C0/G0]4 and tested to find the critical buckling load and post-buckling failure mode

Effects of delamination failure in crashworthiness of laminated composite box structures

The brittle nature of the most of fibre reinforced polymer (FRP) composites causes they show high capability in. absorbing the impact energy in vehicular structures. This energy absorption is introduced by various fracture mechanisms. In this regard, the fracture study is one of the most important areas to be considered in investigating the energy absorption capability of composite box structures. Various fracture mechanisms such as fibre breakage and buckling, matrix cracking and crushing, debonding at the fibre-matrix interface and especially plies delamination play important roles in progressive failure mode and energy absorption of composite tubes. Delamination occurs as results of shear and tensile separation between fronds. The main objective of this research is to study the effects of interlaminar fracture toughness on the progressive energy absorption of composite structures under quasi-static loading. In this regard, Mode-I, Mode-II and mixed-Mode I/II interlaminar fracture toughness of various types of FRP composites with various laminate designs are studied experimentally to investigate the relationship between interlaminar crack propagation and the energy absorption capability and crushing modes of composite structural elements. Plan view of crushed CFRP and GFRP composite box struts The combination of brittle fracture, lamina bending, local buckling and transverse shearing crushing modes was found from experimental studies. New analytical solutions based on friction, bending and fracture mechanisms were proposed to predict the mean crushing force for each of these failure modes. The crushing process of composite boxes was also simulated by finite element software LS-DYNA and the results were verified with the relevant experimental and analytical results

Effect of stitching pattern on composite tubular structures subjected to quasi-static crushing

Extensive experimental investigation on the effect of stitching pattern on tubular composite structures was conducted. The effect of stitching reinforcement through thickness on using glass flux yarn on energy absorption of fiber-reinforced polymer (FRP) was investigated under high speed loading conditions at axial loading. Keeping the mass of the structure at 125 grams and applying different pattern of stitching at various locations in theory enables better energy absorption, and also enables the control over the behaviour of force-crush distance curve. The study consists of simple non-stitch absorber comparison with single and multi-location stitching behaviour and its effect on energy absorption capabilities. The locations of reinforcements are 10 mm, 20 mm, 30 mm, 10-20 mm, 10-30 mm, 20-30 mm, 10-20-30 mm and 10-15-20-25-30-35 mm from the top of the specimen. The effect of through the thickness reinforcements has shown increase in energy absorption capabilities and crushing load. The significance of this is that as the stitching locations are closer, the crushing load increases and consequently energy absorption capabilities are also increased. The implementation of this idea would improve the mean force by applying stitching and controlling the behaviour of force-crush distance curve