Energy Absorption of Pultruded Hybrid GlassGraphite Epoxy Composites under High Strain-Rate SHPB Compression Loading

In this study, the dynamic response and energy absorption characteristics of different combinations of fiber-reinforced pultruded hybrid composites made of unidirectional glass and graphite fiber/epoxy, have been investigated. High strain-rate compression experiments were conducted on cylindrical specimens at an average strain rate of 700 /s using a modified Split Hopkinson Pressure Bar (SHPB). Failure was monitored with a high-speed video camera, and effects of hybridization on the dynamic behavior of pultruded composites were evaluated. It was found that for a given fiber volume fraction, placing glass fibers in the inner core results in a higher ultimate compressive strength, specific energy absorption, and in general a better dynamic performance with lower density.

Dynamic Response of Pultruded Glass-Graphite/Epoxy Hybrid Composites Subjected to Transverse High Strain-Rate Compression Loading

In a previous study, the energy absorption and dynamic response of different combinations of cylindrical fiber-reinforced pultruded hybrid composite samples made of unidirectional glass and graphite fiber/epoxy, were investigated under longitudinal compression loading. It was found that placing glass fibers in the inner core of composites resulted in a higher ultimate compressive strength and specific energy absorption. In this study, the dynamic responses of pultruded glass-graphite/epoxy hybrid specimens with rectangular cross-section subjected to transverse compression loading are reported. Crack initiation and propagation was monitored using a high-speed video camera, and the effects of hybridization were analyzed. It was found that the location of glass or graphite fibers inside the pultruded composites has no significant effect on the ultimate compressive strength under such transverse compression loading. The energy absorption in all the hybrid specimens was almost identical. Graphite/epoxy composite showed higher specific energy absorption due to its lower density, and glass/epoxy composite had the lowest specific energy absorption.

Quasi-Static Flexural Properties of a Pultruded Glass Fiber/Unsaturated Polyester Square Pipe

This paper explores quasi-static flexural properties and fracture behavior of a pultruded glass fiber/unsaturated polyester square pipe for automotive structural applications. Three-point flexural testing is performed in an Instron Universal Testing Machine with steel jigs supporting the top and bottom surfaces of the pipe. Acoustic emission (AE) measurements are recorded during flexural testing to evaluate initial fracture in the pipe structure. After final fracture, five cross-sections of the pipe are cut at 50-mm intervals along the longitudinal axis, with the first cut located at the mid-span of the pipe. Cross-sections of a pipe from an interrupted test where initial fracture is detected from the AE method are also prepared. Damage locations and behavior on each cross-section are observed. The flexural testing results show that the cumulative AE counts increase rapidly from 2.5 kN, that final failure occurs at a maximum load of approximately 13 kN, and that corresponding initial and final failure occurs in the two corner regions on the compressive side of flexural loading. Failure initiates by stress concentrations due to the upper jig on the top surface during bending. The cross-sectional observations also reveal clear deformation behavior of the pipe where failure is present, marked by inward bending of the top surface and upper corners located on the compressive side, near the jig. The locations of maximum stresses and deformations obtained from finite element analysis of this pipe structure are in very good agreement with the experimental observations.

Energy Absorption of Pultruded Glass-Graphite/Epoxy Hybrid Composites under High Strain-Rate Induced Transverse Tension

This paper focuses on the dynamic tensile response of glass-graphite/epoxy composites illustrating improvement in energy absorption through hybridization. The dynamic response and energy absorption characteristics of pultruded hybrid combinations of glass and graphite fibers in an epoxy matrix subjected to induced transverse tension at high strain-rate in a modified Split Hopkinson Pressure Bar (SHPB) apparatus, are presented. Transverse tensile strength was determined by diametral compression of disc samples (Brazilian indirect tensile test method). Diametral crack initiation and strain to failure were monitored with a Shimadzu HPV-2 high-speed video camera at a recording speed of 500,000 fps and Digital Image Correlation (DIC). Adequate measures were taken to ensure that initiation of specimen failure occurred at the exact center of the disc specimen, and propagated through the diameter along the compressive loading axis, for the induced transverse tension tests to be valid. A study of the strength and specific energy absorption demonstrates the benefits of hybridization. Under induced transverse tensile loading condition, the pure glass/epoxy (GL60) exhibited higher strength than pure graphite/epoxy (GR60). Pure graphite/epoxy (GR60) has higher specific energy absorption capacity than pure glass/epoxy (GL60) in transverse tension. Among all hybrids, GR30 has the highest specific energy absorption under transverse tension. Overall, hybrid GL48, with 48% low-cost glass fibers in the inner core and 12% high-cost graphite fibers in outer shell, was found to exhibit better performance under induced transverse tension at high strain-rates, showing the benefits of hybridization.

Civil and structural engineering applications,recent trends,research and developments on pultruded fiber reinforced polymer closed sections:a review

The objectives of this study are to review and evaluate the developments and applications of pultruded fiber-reinforced polymer composites in civil and structural engineering and review advances in research and developments.Several case applications are reviewed.The paper presents a state-of-the-art review of fundamental research on the behavior of pultruded fiber reinforced polymer closed sections and highlights gaps in knowledge and areas of potential further research.

Applications of Glass and Glass Fiber Retrofit Polymer in Modern Footbridges

The architecture of footbridge design takes the form of a number of submissions from leading architects and engineers, each setting out their views on bridge design--present and future. It looks at the functions of a bridge, defining purpose of place and context, the spirit of creativity and the reasoned progression of an idea. It also explores the exploitation of materials technology and construction innovation and the tension between lightness and mass and between sculpture and scale. Present parameters of tempered and laminated glass create possibility of modern architecture of footbridges which are being full of transparency and light reflex effects. Four projects, using glass panels designed by Santiago Calatrava, have been presented in this paper. GFRP （glass fiber retrofit polymer） makes new horizon in material technology, helps to enrich new conception of structure with longer durability, low weight of deck and new creation of architecture line. The paper has described a few results of FEM （finite element method） analysis of footbridge with modular bridge GFRP deck system. The footbridge was excited by impact and human-induced vibrations. Composite material consists of glass fibers and polymer matrix is a promising alternative against traditional materials. New architecture and modern material engineering are looking for fresh possibilities of form and shape of structure, long durability and extraordinary technical parameters of building elements.

On Employment of FRP Elements in Constructions： The Case of an All GFRP Covering for Historic Structure Stroked by Earthquake

The paper shows the approach toward the calculation of one of the bigger PFRP （Pultruded Fiber Reinforced Polymer） structure realized in high seismic zone, i.e., a covering structure of an historic church stroked and partially collapsed by earthquake in L＇Aquila （Italy）, the 4 April 2009. The goal regards the analysis and evaluation of seismic performance of that structure made by very light and elastic-brittle material, as FRP material, in a moment in which there is a loss of technical recommendation for specific calculation in seismic field, indeed actually some deepening already present in literature allows only static field. The covering structure is an all FRP spatial-reticular with elements made by pultrusion process, connection plates by bag molding process and steel bolts. The PFRP structure covers more than 1000 meters squares surface with 32 meters height and only 100 kN weight. Detail performance of first part of PFRP structure through mode vibrations and involved percentage mass deduced by numerical approach with discussion of employment＇s perspectives of PFRP material in seismic zones than traditional material are showed.