The state of considerable number of structurally deficient or functionally obsolete infrastructure in the US, along with the prohibitive cost of replacement has opened a way for the search of innovative methods of rehabilitation. One such method is the use of composite plates adhesively bonded to concrete to prevent the propagation of crack within the concrete structure. Due to their high specific strength and corrosion resistance, composite materials serve better than conventional construction materials. The load transfer and the resulting stress distribution in the composite plate and adhesive layer can be investigated analytically and numerically. In this paper, analytical model is selected and used to analyze and predict the failure conditions of the adhesive. Parametric study is also included to understand the effects of the length and thickness of the adhesion bond, the modulus of the adherents and the adhesive. Finally, a general equation of the adhesion bond strength of the single-lap joint is presented for general shear stress-strain behavior of the adhesive.

Low mold filling time and improper fiber wetting are the main problems faced by the manufacturers applying the Resin Transfer Molding (RTM) process. The objective of this work was to minimize these problems and to study the effect of weirs on the RTM process. A mold was designed such that the lower mold plate contains two weirs, one at the resin inlet port and the other at the outlet port. The purpose of adding the weirs is to provide a continuous inlet stream near the resin inlet port and to cause backpressure near the outlet port to induce complete mold filling. Laminated plates were prepared using glass fibers and epoxy resin (combination of EPON resin-862 and curing agent W). The test parameters investigated, such as void contents, dry spots and mold filling time, were compared with those of samples that were prepared without the use of weirs. It was found that the presence of weirs resulted in significant elimination of dry spots, minimization of void contents and a reduction in mold filling time. As a result, the cost required to manufacture composite parts can be reduced by the use of weirs. In addition to the experimental investigation, a computer simulation (using LCMFLOT software) of resin flow inside the mold cavity was conducted. Many simulations were run in order to optimize the height and shape of the weir. Rectangular weirs of height 2.54 mm showed minimum mold fill time. It was found that the results obtained from the experimental work and flow simulations are in good agreement. Based on this work, it is evident that complex parts can be produced in less cycle time if weirs are positioned at appropriate locations.

Close cell structured foams are made by incorporation of cenospheres in polymeric materials. Low moisture absorption characteristics and considerably higher compressive strength of these materials compared to open cell structured foams make them suitable for use as core materials in sandwich structured materials. Incorporation of cenospheres in the epoxy resins enhances their impact strength and damage tolerance, especially if these materials are used in sandwich configurations. Present study analyzes and compares the effect of incorporation of cenospheres like flyash and glass microballoons in the epoxy resins on the deformation and fracture behavior of the material. Approach based on determination of local stress intensity factors is used to obtain estimate of the stresses in the material.

An analytical model was developed to determine the stress and strain distributions of adhesive-bonded composite single-lap joints under tension. Laminated anisotropic plate theory was applied in the derivation of the governing equations of the two bonded laminates. The adhesive was assumed elastic-perfectly plastic and follows von Mises yield criterion. The entire coupled system was determined through the kinematics and force equilibrium of the adhesive and the adherends. The overall system of governing equations was solved by directly solving the differential equations with appropriate boundary conditions. Computer software Maple was used as the calculation tool in solving these equations. Results from the analytical model were verified with finite element analysis using ABAQUS and also compared with experimental results using specimens defined in ASTM D 3165 “Strength Properties of Adhesives in Shear by Tension Loading of Single-Lap-Joint Laminated Assemblies.” Although all three failure modes of bonded joints, substrate failure, cohesive, and adhesive failure, were present as the test results, only cohesive failure mode was analyzed.

Modeling of the fire performance of fiberglass reinforced composite pipe was investigated in this study. A multidimensional heat transfer model was developed and used to capture the essentials of thermal transport and material decomposition. A finite difference modeling (FDM) numerical approach is used in solving the coupled multidimensional Fourier equation with chemical decomposition response model. The fire resistance of a dry hydrocarbon fire test is simulated in this analysis. Transient temperature distributions in the joined section of a composite-to-composite FRP pipe where failure is most likely to occur were predicted for comparison with experimental results. The FRP materials used in the analysis were E-glass and glass-phenolic.

This work provides a consistent and systematic framework for the gradient approach in coupled damage-plasticity that enables one to better understand the effects of material inhomogeneity on the macroscopic behavior and the material instabilities. The idea of multiple scale effects is made more general and complete by introducing damage and plasticity internal state variables and the corresponding gradients at both the macro and mesoscale levels. The development of evolution equations for plasticity and damage is treated in a similar mathematical approach and formulation since both address defects such as dislocations for the former and cracks/voids for the later.

Deepwater activities are the future of the Offshore Oil and Gas Industry. Huge reserves have been located in the Gulf of Mexico as well as off the Coast of West Africa and Brazil. The development of floating production platforms and vessels offers challenges to the facilities engineer who must consider new materials to meet stringent topsides weight limitations. A critical technology for facilities piping in offshore platforms is joining technique. This paper discusses the development of a hybrid joining approach by using heat-activated coupling and adhesive bonding. The technique procedure is presented via specimen fabrication. A total of eleven coupled specimens are prepared and evaluated using standardized internal pressure tests. The feasibility of this new joining technique in offshore piping is discussed based on the internal pressure test results.

We observe two different events happening in a Matagorda Island area. Faults may act as a seal and enhance the shale sealing. Changes in pore pressure calculated from sonic/resistivity logs are steep, “transitional” zone is about a 100–150′ thick and almost invisible at a whole well scale. Because of such sharp changes these zones are hard to recognize on MWD, however typically one casing point required to separate it from upper normally pressured section. Another option — fault causes partial damage, possibly through micro-fractures in shales. Shale sealing properties are decreased pore pressure in reservoir sands is lower, that in neighboring blocks. Sealing zone possess gradual changes in pore pressure with lower values that expected. Such zones are up to 2000′ thick and could be observed on MWD as well as on conventional log diagrams. Several casing points required in order to drill through such zone. By incorporating this information into the geological model one can predict whether the fault will act as a pressure-formation liquids “semi-conductor” or as a good seal. Faults that damage the seal above overpressured zone might result in unexpected shallow overpressure and/or shallow gas. Such faults should be determined, mapped and avoid when possible from drilling.

Modeling of heat-activated coupled graphite fiber reinforced composite piping in a cryogenic environment was investigated in this study. A 2-dimensional heat diffusion model was used to capture the essentials of thermal transport through the thickness of a heat-activated coupled (HAC) graphite epoxy composite-to-composite pipe joint. The resulting boundary value problem was solved using an Alternating Direction Implicit (ADI) finite difference model (FDM). Simulated numerical transient temperature distributions are predicted for comparison with experimental results.

A rate dependent, non local approach is developed in this work for geo-materials. A multi-scale gradient theory is addressed for non local approach. Visco-plasticity is also incorporated for an additional regularization of the local behavior. The plastic spin is incorporated to separate the effect of micro-structural rotation from the gradient effect. The flow characteristics of the soil is also incorporated in order to separate the viscosity effect from the flow effect.

The curing process of epoxy prepreg was studied by means of Differential Scanning Calorimeter. The dynamic, isothermal, and combinations of dynamic and isothermal measurements were done over selected temperature ranges and isothermal cure temperatures. The heats of reaction for dynamic and isothermal cure were determined. The results show that the heat of isothermal-cure reaction increased with the increment of temperature. The degree of cure was calculated from the heat of isothermal-cure reaction. The complete cure reaction could be achieved at 220 °C within the very short cure time. The changes of cure rate with time were given for the studied isothermal cure temperatures. To simulate the relationship between the cure rate and degree of cure, the autocatalytic model was used and the four parameters were calculated. Except in the late stage of cure reaction, the model agrees well with the experimental data, especially at high temperatures. To account for the effect of diffusion on the cure rate, a diffusion factor was introduced into the model. The modified model greatly improved the predicated data at the late stage of cure reaction.

The development of international standards for composite piping systems that are used in the Marine and Offshore Oil & Gas Industries is a recognized customer need. These industries are global in nature. It is not uncommon to see project specifications written in London and Houston, fabrication of the vessel hull in a Korean yard, topsides construction in Indonesia and project location off the coast of West Africa. Operator supplied specifications could come from The Netherlands, France, Norway as well as numerous other countries. In addition, certifying agencies such as ABS, Lloyds or DNV could be involved that must follow international maritime rules and regulations. A concerted effort has been made within the past five years to address these issues. Operators worldwide have come together with composite pipe manufacturers, engineering firms and certifying agencies to develop international standards that address these issues. Anyone considering the use of composite piping in the Marine and/or Offshore Oil & Gas Industries should consider the ASTM and ISO Standards that are in the final stages of development. ASTMF-1173 Rewrite is a purchasing document that is being balloted at the present time. It was developed by ASTM F25.13.03 workgroup. ISO WD 15840 is the international version of ASTM F-1173 Rewrite. It has been circulated to the international community for comments. It was developed by ISO/TC8/SC3/WG4. ISO WD 14692 is a rewrite of original United Kingdom Offshore Operators Association (UKOOA) document that was adopted in March 1994. It has been circulated to the international community for comments and is in it’s final stage of development. It was developed by ISO/TC 67/SC 6/WG 5. This document is an engineering specification and recommended practice document. When finalized and passed by the various committees ISO 15840 and ISO 14692 should be used in conjunction with each other. They are compatible documents based on performance criteria. It is the opinion of many who have been in the composite pipe business for over 20 years that these are the most important documents ever developed by our industry. They are grossly overdue. However, while standards are a recognized customer need, standards that are not fully understood by operators, piping engineers and installation teams can be dangerous and misinterpreted. Knowledge of the unique properties of composite materials must be a perquisite to those using these standards. Standards that are not fully understood in the hands of the uneducated is a formula for disaster.

An experimental study on ultrasonic welding of thermoplastic, which is a prelude to study how the technology can be adapted to join composite materials, was conducted. Three sets of specimen were studied to investigate the influence of energy guide on the bonded specimen. No major statistical difference between the ‘energy guides’ of the tested thermoplastic Celuka™ coupons were noted. Failure of the welded specimen was by shear at the interface. A 75% drop in strength for the bonded material was observed.

A study in collaboration between investigators at Southern University and Louisiana State University in Baton Rouge, Louisiana and NASA/MSFC is examining materials for modeling and analysis of heat-activated thermal coupling for joining composite to composite/alloy structures. The short-term objectives of this research are to develop a method for joining composite or alloy structures, as well as to study the effects of thermal stress on composite-to-alloy joints. This investigation will result in the selection of a suitable metallic alloy. Al-Li alloys have potential for this purpose in aerospace applications due to their excellent strength-to-weight ratio. The study of Al-Li and other alloys is of significant importance to this and other aerospace as well as offshore related interests. Further research will incorporate the use of computer aided design and rapid prototype hardware for conceptual design and verification of a potential composite piping delivery system.

Over the last few years the number of standards relating to the use and implementation of GRP pipelines and piping systems has dramatically proliferated. A working group under ISO TC 67 was formed in an attempt to produce a single international standard with the aim to amalgamate and harmonise the many country wide standards. Standards that were considered in this amalgamation included ASTM F 1173, API 15 HR, BS 7159, ASME B31.3 and the Shell DEP. The work group consisted of members from the oil and gas industry, suppliers and local Health and Safety Executives. The basis of the document was the old UKOOA specification for the GRP for off-shore systems. The scope of the this new ISO standard was broadened in terms of both application and service conditions. The new ISO standard comprises 4 sections, scope, qualification, system design and installation/operation. The key points of the sections are; Qualification procedures are performance based, i.e. the emphasis is on suppliers to demonstrate performance. Care was taken with this new standard to minimise the test burden without compromising on technical rigour. System design procedures were defined which balanced existing design practices and experience with the limited amount of technical data. Installation and operational procedures were selected to enhance the use of GRP in many applications. Typical damage mechanisms and defects that could possibly occur were documented with recommendations made of relevant inspection techniques and repair options. The issue date for this ISO standard is mid 2001.

Glass Fiber Composite laminates were subjected to low velocity impact at 2 m/s using a semi-hemispherical drop tower tup. Impact damage were observed and recorded over a wide range of temperatures. Of particular interest is the post impact strength at these test temperatures. The effect of temperature variation on the impact damages and on the residual compressive buckling strength and elastic modulus is evaluated based on the test results.

In this study, an E-glass fiber reinforced epoxy composite laminate is subjected to ultraviolet radiation (UV) for up to 48 hours. The intensity of the ultraviolet radiation is 1.5 J/cm 2 /min. A total of 42 specimens are prepared and tested, in which 6 specimens are used as control and 36 specimens are conditioned. For the conditioned specimens, 18 specimens are exposed to air and 18 specimens are immersed in a water base while subjected to UV radiation. Low velocity impact tests are conducted on the conditioned specimens and control specimens using instrumented drop-weight impact machine. Compression after impact (CAI) tests are conducted using a MTS machine to determine the residual load carrying capacity of the impact damaged specimens. Microscopic observation is conducted to aid in the analysis of the damage mechanism. The test results show that UV radiation alone has a significant effect on reducing the residual load carrying capacity of impact damaged laminated composites. The presence of water enhances the damage effect of UV radiation.

There are many methods available for designing GRP (glass reinforced plastic) piping systems for internal pressure. These include short term methods such as those found in ASME RTP-1 and long term methods such as ASTM D2996. Other standards, such as ASME B31.3, ASTM F1173, and ABS Rules for Steel Vessels and MODUs, provide options for both long term and short term methods. ASME RTP-1 goes one step further by allowing a design process based on design calculations only. This paper will provide the details for designing GRP piping systems according to a new standard, ISO 14692. This method involves generating a design envelope to address all stresses from the design conditions of the system. This paper will also provide a comparison of this method’s advantages and disadvantages to other standards currently in use.