Ahmad Rivai

Parameter Study of Tool-Laminate Interface through Simulation for Composite Manufacturing Using Autoclave Process

Modeling the spring-back requires tool-laminate interaction to be taken into account. In this study, an interface based on orthotropic linear behavior coupled with an out-of-plane shear stress failure was proposed to simulate the tool-laminate interaction. The results from this particular model captured the out-of-plane shear stress distribution. The model allows predicting the warpage displacement in function of interface properties; shear modulus and shear stress failure which leads to the construction of Chart Design. Additionally, the influence of the number of plies was studied as well and the evolution of the maximum warpage agreed with the literature.

Spring-back simulation of unidirectional carbon/epoxy L- shaped laminate composites manufactured through autoclave processing

This paper presents an original method in predicting the spring-back for composite aircraft structures using non-linear Finite Element Analysis (FEA) and is an extension of the previous accompanying study on flat geometry samples. Firstly, unidirectional prepreg lay-up samples are fabricated on moulds with different corner angles (30o, 45o and 90o) and the effect on spring-back deformation are observed. Then, the FEA model that was developed in the previous study on flat samples is utilized. The model maintains the physical mechanisms of spring-back such as ply stretching and tool-part interface properties with the additional mechanism in the corner effect and geometrical changes in the tool, part and the tool-part interface components. The comparative study between the experimental data and FEA results show that the FEA model predicts adequately the spring-back deformation within the range of corner angle tested.

Effect of Reprocessing Palm Fiber Composite on the Mechanical Properties

Concern for the environment, both in terms of limiting the use of finite resources and the need to manage waste disposal, has led to increasing pressure to recycle materials at the end of their useful life. This work describes the effects of reprocessing on the mechanical properties of oil palm fiber reinforced polypropylene composites (PFC). Composites, containing 30wt% fiber with 3wt% Maleate Polypropylene as a coupling agent, were reprocessed up to six times. For this composite, tensile strength (TS) and Young modulus (YM) were found to decrease by 9.6% and 4.7% after being reprocessed for six times. Flexural strength was found to decrease by 23.8% with increased number of reprocessing. The hardness numbers of the composite were found to increase by 7.43% from 72.10 to 77.89 after the sixth reprocessing. In general the degradation on the mechanical properties is considered to be small and PFC has potential to be reprocessed.

Design and Analysis of an Aircraft Composite Hinge Bracket Using Finite Element Approach

The use of composite materials in aircraft structures have been increasing for the past decade. The anisotropic and heterogeneous nature of composites remains a major challenge to the design and analysis of composite aircraft structures. Composite structures require a different design approach compared to the design of metallic structures. This paper aims to provide a step by step definitive guide to design and analyze composite structures using finite element approach. A simplified design model for the composite structural design was used to analyze an aircraft composite hinge bracket. The composite hinge bracket which is made of IM7/8552 laminated composite plates was successfully designed with a margin of safety of 0.216 and a weight savings of 43.77 percent was estimated.

Effect of Stacking Layup on Spring-back Deformation of Symmetrical Flat Laminate Composites Manufactured through Autoclave Processing

The residual stresses that develop within fibre-reinforced laminate composites during autoclave processing lead to dimensional warpage known as spring-back deformation. A number of experiments have been conducted on flat laminate composites with unidirectional fibre orientation to examine the effects of both the intrinsic and extrinsic parameters on the warpage. This paper extends the study on to the symmetrical layup effect on spring-back for flat laminate composites. Plies stacked at various symmetrical sequences were fabricated to observe the severity of the resulting warpage. Essentially, the experimental results demonstrated that the symmetrical layups reduce the laminate stiffness in its principal direction compared to the unidirectional laminate thus, raising the spring-back warpage with the exception of the [45/-45]S layup due to its quasi-isotropic property.

The Effect of Heat Treatment on Fatigue and Mechanical Properties of 6061 Aluminium Alloy

This paper investigated the effect of heat treatment on mechanical properties and microstructure of 6061 aluminium alloy. The aluminium alloys were examined in the heat treated conditions, using different quenching media, water and oil. The alloy was solution heat treated at temperature of 529oC for one, three and five hour respectively. Aging treatment was carried out at temperature of 160oC which is assumed to be the best temperature for ageing process. Hardness measurement was carried out using a Brinell Hardness Tester Machine. The results shows hardness and impact strength are inversely proportional to each other, as the hardness of 6061 aluminium alloy decreases and impact strength increases.

Review on Fluid Structure Interaction Solution Method for Biomechanical Application

Fluid-Structure Interaction engages with complex geometry especially in biomechanical problem. In order to solve critical case studies such as cardiovascular diseases, we need the structure to be flexible and interact with the surrounding fluids. Thus, to simulate such systems, we have to consider both fluid and structure two-way interactions. An extra attention is needed to develop FSI algorithm in biomechanic problem, namely the algorithm to solve the governing equations, the coupling between the fluid and structural parameter and finally the algorithm for solving the grid connectivity. In this article, we will review essential works that have been done in FSI for biomechanic. Works on Navier–Stokes equations as the basis of the fluid solver and the equation of motion together with the finite element methods for the structure solver are thoroughly discussed. Important issues on the interface between structure and fluid solvers, discretised via Arbitrary Lagrangian–Eulerian grid are also pointed out. The aim is to provide a crystal clear understanding on how to develop an efficient algorithm to solve biomechanical Fluid-Structure Interaction problems in a matrix based programming platform.

V-Bend Die Forming Performance of Oil Palm Fiber Composite

Composite materials have steadily gained recognition worldwide for its uses in various sectors such as aerospace, infrastructures and automotive industries. In stamp forming of V-bend die, the most sensitive feature is elastic recovery during unloading called spring-back. This phenomenon will affect bend angle and bend curvature. This research studies the effects of tool radius, feed rate, temperature and weight ratio of fiber to Polypropylene on the spring-back of palm fiber composite. Analyzed results obtained from Design of Experiment (DOE) shows temperature, fiber composition followed by feed rate gives significant effect towards spring-back. The suggested temperature, fiber composition and feed rate to get the smallest spring-back angle in the current study are 150°C, 30wt% and 500mm/min.

Modelling optimization involving different types of elements in finite element analysis

Finite elements are used to express the mechanical behaviour of a structure in finite element analysis. Therefore, the selection of the elements determines the quality of the analysis. The aim of this paper is to compare and contrast 1D element, 2D element, and 3D element used in finite element analysis. A simple case study was carried out on a standard W460x74 I-beam. The I-beam was modelled and analyzed statically with 1D elements, 2D elements and 3D elements. The results for the three separate finite element models were compared in terms of stresses, deformation and displacement of the I-beam. All three finite element models yield satisfactory results with acceptable errors. The advantages and limitations of these elements are discussed. 1D elements offer simplicity although lacking in their ability to model complicated geometry. 2D elements and 3D elements provide more detail yet sophisticated results which require more time and computer memory in the modelling process. It is also found that the choice of element in finite element analysis is influence by a few factors such as the geometry of the structure, desired analysis results, and the capability of the computer.

Preliminary Investigation on the Perforated Panel Mobility Using Finite Element Method

Introduction of holes into plat-like structures is commonly found as one of practical noise control measures to reduce sound radiation. However, perforation into the panel also reduces the panel stiffness and hence increases its vibration. Since the discussion and also the analytical model to quantify this effect are lacking, this paper discusses the dynamics of a perforated panel from the results obtained using Finite Element Method (FEM). Different hole geometries are simulated to investigate their effect on the plate mobility. It is found that increasing the perforation ratio increases the plate mobility particularly at off-resonance peaks. The effect of hole size and number are also discussed in this report.