This research proposal aims to study the failure criteria of fibrous composite materials. The researcher will evaluate existing composite failure criteria in finite element analysis software and explore modifications to account for large deformations, progressive failure, and stress-strain interactions. Several composite failure theories will be presented and their advantages/limitations in modeling laminate failure will be discussed. Experimental testing will be conducted to validate the analysis results. The research intends to improve understanding and modeling of failure in fibrous composites.

1. RESEARCH PROPOSAL
A Study of Failure Criteria of Fibrous
Composite Materials
Name: G. Sudhakar
Qualification: M.E.
Designation:Associate Professor
Date: 30-11-2017

2. ABSTRACT
Fibrous composites are materials consisting of lightweight, high modulus fibers inbedded in a
surrounding material called the matrix. These composites have properties that vary with the
direction of interest. These fibrous composite material comprising carbon fibres and chemically
delaminated vermiculite lamellae are produced of the material by applying a suspension
(preferably an aqueous suspension) of the lamellae to carbon fibres and removing the liquid
medium from the suspension. The composite material is useful for the insulation and fire-
protection of substrates.

3. Scope of work:
(1) evaluation of existing composite failure criteria in the nonlinear, explicit transient
dynamic finite element code
(2) exploration of the possibilities for modification of material and failure models to
account for large deformations, progressive failure, and interaction of damage accumulation with
stress/strain response of laminated composites.
These Composite materials exhibit various and complex failure behavior. Different formalisms
have been used to predict failure. Improvement of old theories and new ones continue to be
published. In this paper, the most recent and widely used models are presented. Failure criteria
such as Tsai-Wu, parametric formulations, maximal stress and strain, Hashin criterion, Hart-Smith
criterion, and the method based on kriging are presented. These failure theories may be classified
in two categories, depending whether they integrate failure modes or not. The formalism of each
theory is briefly described and their application to model failure of composite laminates is
discussed by comparing the advantages and limitations of each method. The diversity of
experimental failure envelopes, as reported in the literature on composites, is outlined and it is
shown that most criteria permit modeling only particular failure properties of composite laminates.

4. Organisations proposed: Defense Metallurgical Research Laboratories (DMRL), Misra
Dathu Nigam (MIDHANI).
Research Methodology:
Many criteria have historically been proposed to predict failures in these composites.
Prediction of the failure of the matrix (also called inter-fibre failure) has traditionally been assigned
to a certain interaction (typically quadratic) between the components of the stress vector associated
to the plane of failure. In this paper, a revision of these proposals is first of all carried out in order
to examine in greater depth the implications of some of them. Then, a micromechanical study is
conducted considering, based on failure observations, that the mechanism of failure starts with a
crack running between the fibre and the matrix. The objective of this micromechanical analysis is
to elucidate whether the assumption that the stress vector associated to a plane controls the failure
of the plane is physically based. The numerical analysis is performed using the Boundary Element
Method, allowing contact between the debonded surfaces of fibre and matrix. Different
combinations of loads are applied (perpendicular and parallel to the plane of failure) to check their
influence in the energy release rate, which is the fracture parameter evaluated. The results obtained
prove numerically that stresses not associated to the macromechanical plane of failure play an
important role in the micromechanism of failure of fibrous composites.

5. This fact has been experimentally checked by means of the performance of a series of two
dimensional loading tests.

6. Conclusion
Fibrous composite materials in dental and orthopaedic applications have been introduced. In dental
application, composite materials are required with good aesthetic and mechanical properties
besides good biocompatibility. On contrast, orthopaedic application needs materials which have
excellent mechanical property and biocompatibility in order to sustain severe mechanical
environment. In both applications, effective reinforcing ways using textile performs and interface
property of composite have not been proved. Consequently, there is more discussion point about
the feasibility of composite materials in dental and orthopaedic applications. Therefore, in this
report, dental composite products (dental post, orthodontic archwires and brackets) which paid
attention to the usage of textile preform and proper interface control were firstly introduced. It was
clear that textile preform is greatly useful to obtain the functional mechanical requirement in dental
post and orthodontic brackets. The importance of interface control to obtain the best mechanical
performance was also shown in aesthetic composite archwire. Novel fabrication method of textile
carbon/PEEK composites which may be applied to several orthopaedic applications was
introduced.
Usage of fibrous composite materials in dentistry and orthopaedics
References:
1. J.S Bradley, G.W Hastings, C Johnson-Nurse Carbon fibre reinforced epoxy as a high
strength, low modulus material for internal fixation plates
2. W.H Akeson, R.D Coutts, S.L.-Y Woo Principles of less rigid internal fixation with plates
3. S.L.-Y Woo, W.H Akeson, R.D Coutts, L Rutherford, D Doty, G.F Jemmott, et al. A
comparison of cortical bone atrophy secondary to fixation with plates with large differences
in bending stiffness

7. 4. H Toyoizumi, F Watari, T Imai, S Yamagata, M KobayashiFabrication of aesthetic wires
with flexural and torsional stiffness by photo curing method
5. R.H MullarkyAramid fiber reinforcement for acrylic appliances
6. M DiamondResin fiberglass bonded retainer
7. A Patel, C.J Burstone, A.J GoldbergClinical study of fiber-reinforced thermoplastic as
orthodontic retainers
8. Kotaki M. Fracture mechanism of woven fabric composites. PhD thesis, Kyoto Institute of
Technology; 2000.
9. G.S SolnitThe effect of methyl methacrylate reinforcement with silane-treated and
untreated glass fibers
10. A Jancar, A.T DibenedettoFiber reinforced thermoplastic composites for dentistry, Part I
Hydrolytic stability of the interface