Search results

The purpose of this paper is to synthetically investigate the impact damage responses of carbon fiber reinforced polymer (CFRP) and its influence on the compression mechanical responses of CFRP laminates, including damage distribution, residual compressive strength and fracture morphology.

A progressive damage simulation model is developed to analyze the complicated damage responses of CFRP laminates that are manufactured by resin transfer method (RTM) technology. Based on the ABAQUS/explicit finite element analysis solver, a VUMAT code is proposed to descript the composite materials’ damage behaviors under both impact and compression load. Adopting this proposed model, the primary mechanical indicators of four groups’ 5284RTM/U3160 CFRP laminates with different stacking sequences are predicted. Moreover, impact and compression after impact tests are conducted to verify the accuracy of simulation results.

Both simulation and experimental results show that the impact damage with low visible detectability can significantly reduce composites’ compressive strength. For all four groups’ composite laminates, the residual strength ratio is around 35% or even lower. The kernel impact damage near the plates’ geometric center promotes the degradation process of local materials and finally leads to the early occurrence of mechanical fracture. In addition, the impact damage projection area is not sensitive to the parameters of stacking sequences, while the residual compression strength is proportional to the number of 0-degree layers within whole laminates.

This study helps to understand the effect of an impact event on CFRP laminates’ compressive bearing capacity and provides a numerical method in simulating the damage responses under both impact and compression load.

Lastform, a three year EPSRC (IMI) programme, has investigated metallic laminating techniques to produce large‐scale production capable tooling. This work is intended as an overview of the research and development performed at the University of Warwick’s Warwick manufacturing Group. The programme was a collaboration between seven industrial partners and three universities with each university having a discreet area of research. The focus at Warwick was to establish robust methods of joining metal sheets to form tools for different production processes. Bonding mediums, test parts for process evaluation, sample tools and production tools are described. The advantages of metal laminating for different processes are evaluated. Results include reduced lead‐time and cost savings and enhanced processing capability by the use of conformable heating or cooling channels.

Among various efforts pursued to produce fuel efficient vehicles, light weight engineering (i.e. the use of low‐density structurally‐efficient materials, the application of advanced manufacturing and joining technologies and the design of highly‐integrated, multi‐functional components/sub‐assemblies) plays a prominent role. In the present work, a multi‐disciplinary design optimization methodology has been presented and subsequently applied to the development of a light composite vehicle door (more specifically, to an inner door panel). The door design has been optimized with respect to its weight while meeting the requirements /constraints pertaining to the structural and NVH performances, crashworthiness, durability and manufacturability. In the optimization procedure, the number and orientation of the composite plies, the local laminate thickness and the shape of different door panel segments (each characterized by a given composite‐lay‐up architecture and uniform ply thicknesses) are used as design variables. The methodology developed in the present work is subsequently used to carry out weight optimization of the front door on Ford Taurus, model year 2001. The emphasis in the present work is placed on highlighting the scientific and engineering issues accompanying multidisciplinary design optimization and less on the outcome of the optimization analysis and the computational resources/architecture needed to support such activity.

This paper gives a bibliographical review of the finite element methods (FEMs) applied to the analysis of ceramics and glass materials. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published between 1977‐1998. The following topics are included: ceramics – material and mechanical properties in general, ceramic coatings and joining problems, ceramic composites, ferrites, piezoceramics, ceramic tools and machining, material processing simulations, fracture mechanics and damage, applications of ceramic/composites in engineering; glass – material and mechanical properties in general, glass fiber composites, material processing simulations, fracture mechanics and damage, and applications of glasses in engineering.

T-sections of carbon fibre-reinforced composites are prone to delamination because they lack reinforcement through their thicknesses. The purpose of this paper is to present the structural response of cost-effective laminated T-sections when subjected to various types of loads and impacts.

The core of the automated manufactured beams is analysed. Pull-off, flange tension, and flange bending were tested for specimens extracted from an I-beam. The failure processes for all of the specimens were investigated in detail, leading to the statistical evaluation of the failure modes.

A correlation is apparent between the impact damage energy and certain fracture patterns. These results can be used to assess damage tolerance when designing stiffeners, beams, and various complex structures. The increase in strength by 25 per cent was measured for the advanced stitching located in the web section for the flange tension test.

The resistance displayed by the T-sections toward impact damage was studied experimentally, as the literature describing this topic is limited. The prevalence of one fracture mode for higher impact energies shows a possible advantage of the cost-effective preforms for the damage tolerant philosophy.

This paper gives a review of the finite element techniques (FE) applied in the area of material processing. The latest trends in metal forming, non‐metal forming, powder metallurgy and composite material processing are briefly discussed. The range of applications of finite elements on these subjects is extremely wide and cannot be presented in a single paper; therefore the aim of the paper is to give FE researchers/users only an encyclopaedic view of the different possibilities that exist today in the various fields mentioned above. An appendix included at the end of the paper presents a bibliography on finite element applications in material processing for 1994‐1996, where 1,370 references are listed. This bibliography is an updating of the paper written by Brannberg and Mackerle which has been published in Engineering Computations, Vol. 11 No. 5, 1994, pp. 413‐55.

This paper details the development of a rapid tooling manufacturing route for the gravity and high‐pressure die‐casting industries, resulting from an EPSRC funded collaborative research project between the Universities of Warwick, Loughborough and DeMontfort, with industrial support from, amongst others, MG Rover, TRW Automotive, Sulzer Metco UK Ltd and Kemlows Diecasting Products Ltd. The developed process offers the rapid generation of mould tools from laser‐cut laminated sheets of H13 steel, bolted or brazed together and finish machined. The paper discusses the down‐selection of materials, bonding methods and machining methods, the effect of conformal cooling channels on process efficiency, and the evaluation of a number of test tools developed for the industrial partners. The paper also demonstrates the cost and time advantages (up to 50 and 54 per cent, respectively) of the tooling route compared to traditional fabrication methods.

A novel development process aims at finding solutions for lightweight stiffened shell structures and their efficient production. To respect the strong interdependency of structural design and production planning, particularly observed for composite structures, it is of high interest to start considering production effects in early development phases. This integrated approach requires an integrated representation of structure and production. The purpose of this study is to investigate the scope of relevant data and to find a structure for its representation.

The development task is analyzed and a system of so-called solution dimensions is presented, which covers all important aspects of stiffened shell structures and their production. An integrated product data model is developed to cover all of the solution dimensions.

The product data model consists of five coherent partial models. It is explained how these models are defined and how they are connected to each other. An academic example of an aircraft fuselage panel is used to demonstrate the definition process. It is shown how even complex structural concepts are defined systematically.

It is explained how this integrated product data model is used in a software project for the development of aircraft fuselage structures.

The presented approach for the definition and representation of stiffened shell structures enables the developer, e.g. of aircraft fuselage, to respect the crucial criterion of manufacturability from early development phases on. Further, new design approaches, e.g. as inspired by topology optimization, can be considered.

Satisfying the demanding requirements of the aerospace industry requires materials to have optimum levels of strength and toughness combined with good fatigue characteristics and the ability to retain superior features under widely varying conditions of loading and temperature. Recent developments in production and applications have highlighted these advances both in aircraft flying and pointing the way to likely uses in the future.