Shock loading of three-dimensional woven composite materials
Introduction
The interest in the response of plates, shells and other structures to dynamic impulse loading has been renewed in recent years. Most of the studies have focused on homogeneous materials because of their traditionally widespread use in transportation, defense, building, and shipping. However, the advent of composite materials has channeled the interest toward these new materials. Particularly, reference book [1] presents geometrically nonlinear theory, dynamic deformation and failure analysis methods for laminated composite cylindrical shells exposed to longitudinal and lateral blast-type loadings.
Traditionally, two methods have been used to experimentally study the response of various structures subjected to shock loading: the direct use of explosives and the use of a shock tube. The use of explosives to create blast loading has been widely adopted due to the relative ease of use [2], [3]. However, this methodology is plagued with some deficiencies such as the generation of spherical wave fronts and complex pressure signatures that are hard to model. Additional difficulties arise from the complexity of the instrumentation needed to capture the propagating wave. The alternative use of a shock tube is adopted in this study.
Shock tubes have been widely used in the study of supersonic gas dynamics and they allow the creation of either shock or expansion waves. Shock tubes also offer the advantage of generating plane wave fronts and experimental parameters that can be easily controlled and measured.
Previous studies of blast-loaded plates have featured fully clamped or built-in edges [4], [5]. Depending on the magnitude of the impulse, three distinct failure modes have been identified. Mode I failure is regarded as large deformations (elastic/inelastic) with the critical factor being the displacement of the center of the plate. Within Mode I failure, there are two deformation patterns, as described by Ross [6]. The first is a continuous deformation pattern, which is found in near-static loading cases and the second is the development of a plastic hinge, in which the initial deflection of the plate is a traveling plastic hinge. Mode II failure has been defined as a combination of the deformation and tearing of the material along the clamped edges. Mode III failure consists of shearing failure at the boundary with minimal deformation of the plate itself.
Previous studies have considered mostly metallic plates, but recently many researchers have refocused on composites and concrete. The aim of these recent studies was to analyze damage area, midpoint transient deflection, permanent deflection, and other characteristics of dynamic response.
Experimental studies that have been recently performed on metal plates have measured dynamic response, failure modes, and permanent deformations. Studies by Jacinto et al. [3] and Stoffle et al. [2] have focused on the dynamic response of plates when subjected to varying levels of blast and shock loading. Particularly, Jacinto et al. [3] attached accelerometers to the non-impact face of the plates in order to measure the dynamic response, whereas Stoffel et al. [2] used a capacitance scheme to measure central deflection during loading. Experimental studies performed by Nurick et al. [4], [5] and Wierzbicki and Nurick [7] examined the large deformations and failure modes of thin plates subjected to blast loading. The plates were loaded with a pressure pulse of short duration generated by a shock tube.
Composite studies have focused on damage area and on the mechanical properties of the plate material before and after loading [8], [9]. Three types of damage have been observed: matrix cracking, delamination/debonding, and penetration. Matrix cracking consists of circumferential cracks at varying distances from the blast center and radial cracks propagating from the center of the plate. Delamination/debonding damage consists of a discoloration of the area immediately surrounding the central point. This damage mode has been found to be the predominant mechanism in thicker specimens due to high flexural rigidity. Penetration consists of complete fiber failure and, therefore, rupture of the plate.
Recent progress in design, manufacturing and applications of 3-D woven fabrics and composites based on 3-D woven preforms is described in Bogdanovich et al. [10], Mohamed et al. [11]. Particularly, improved experimental results have been obtained in applications of 3-D woven fabrics and composites for various personal and vehicle protection systems (see [12], [13], [14], [15]). Due to their characteristic reinforcement architecture, where through-thickness fibers effectively bridge in-plane cracks, 3-D woven composites do not delaminate and do not allow the initiated microcracks to grow into macrocracks, which makes a strong positive effect on the damage tolerance, ability to withstand multiple shots, and resistance against impact and blast loads.
3TEX manufactures a variety of proprietary 3-D woven fabrics for use in high performance, light-weight, multi-hit, and multi-threat armor systems. These 3-D woven fabrics allow for unique engineered armor systems capable of defeating wide variety of threats that include armor piercing projectiles and projectiles from improvised explosive devices. 3TEX’s 3Weave™ fabrics can be woven using almost any high performance fiber type and can be hybridized by including several different fibers types in a single preform to take advantage of each fiber type performance capabilities. In spite of their relatively large thickness, 3Weave™ fabrics are sufficiently conformable and extremely permeable for common epoxy and epoxy-vinyl ester resin systems. Therefore, 3Weave™ fabrics are ideal materials for pre-pregging, RTM and VARTM technologies. As demonstrated by extensive experimental studies in the last 5 years, 3Weave™ fabrics are very suitable and cost effective materials for manufacturing armor products such as body armor inserts, helmets, vehicle armor systems, ballistic shields and barriers, etc.
The present work is a new experimental investigation of the effects of shock loading on composite plates made of 3Weave™ fabric preforms. The composite plates are subjected to increasing shock loads applied by a shock tube. Real-time measurements of the pressure pulses affecting the plates are recorded and documented for future numerical modeling. Post-mortem studies are used to evaluate the effectiveness of the materials to withstand these shock loads. This testing consists of visual damage observations, compressive strength measurements, and permanent deformation mapping. In the following sections, the methods used to carry out these experiments are presented, and the obtained experimental results are discussed in detail.
Section snippets
Composite materials for experimental studies
The schematic fiber architecture in a typical 3Weave™ fabric is illustrated in Fig. 1a. Here, red yarns run in warp, dark blue yarns in fill and light blue yarns in through thickness (Z) directions, respectively. This idealized model assumes rectangular cross-sections of the yarns. Such assumption, though supported by visual observations, is not imperative; the yarn cross-sections can be considered, for example, as elliptical or lenticular. The yarn paths in this idealized fabric model run
Shock loading apparatus
A shock tube is used to generate a gas flow with conditions that are difficult to create by other methods, such as high velocity, pressure, density, and temperature, although they are only achieved for a very short duration of time (<50 ms). In its basic form a shock tube consists of a long rigid cylinder, divided into a high-pressure driver section and a low pressure driven section separated by a diaphragm. When the pressure differential across the diaphragm reaches a critical value, rupture
Shock tube calibration
The study was initiated by developing a relationship between the diaphragm burst pressure and the reflected pressure experienced by the test plate. To measure this parameter, a pressure transducer was mounted directly to the center of a steel plate. The reflected pressure profiles were measured using a dynamic pressure transducer, model 134A23 from the PCB Piezotronics Company, chosen for its very fast rise time which makes it suitable for highly dynamic measurements. The transducer has a
Conclusions
The primary goal of this research was to study the effects of shock loading on the mechanical properties of four 3-D woven composite materials having different fiber architectures and different thicknesses/areal weights. The post-mortem study was focused on visual observations of the damage zones, measurements of the residual compressive strength, and permanent deflection mapping.
The visual observations of the panels after shock loading showed several distinct signs of damage on the surface and
Acknowledgements
The financial support of the URI Transportation Center under grant numbers 500-2304-0000-0000057 and 500-2304-0000-0000507 and the Office of Naval research under grant number N000140410268 is greatly acknowledged.
The authors are grateful to Mr. Robert A. Coffelt (3TEX) for providing some of experimental composite test specimens.
References (22)
Non-linear dynamic problems for composite cylindrical shells
(1993)- et al.
Shock wave loaded plates
Int J Solids Struct
(2001) - et al.
Experimental and computational analysis of plates under air blast loading
Int J Impact Eng
(2001) - et al.
Deformation and tearing of blast loaded stiffened square plates
Int J Impact Eng
(1995) - et al.
The deformation and tearing of thin square plates subjected to impulsive loads—an experimental study
Int J Impact Eng
(1996) Response of flat plates subjected to mild impulsive loading
Shock Vib Bull
(1974)- et al.
Large deformation of thin plates under localized impulsive loading
Int J Impact Eng
(1996) The damage to stitched GRP laminates by underwater explosion shock loading
Compos Sci Technol
(1995)- et al.
Experimental investigation into the response of Chopped-Strand Mat Glassfibre laminates to blast loading
Int J Impact Loading
(2002) - et al.
A new generation of composites reinforced with 3-D woven fabric preforms
A new generation of 3D woven fabric preforms and composites
SAMPE J
Cited by (100)
Flexible materials and structures for mitigating combined blast and fragment loadings–A review
2023, International Journal of Impact EngineeringExperimental and numerical investigation of vertical shock tube performance for blast load testing of geological media
2023, International Journal of Pressure Vessels and PipingBlast failure and energy analysis of rubber-modified carbon-fiber vinyl-ester composite laminates
2023, Mechanics of MaterialsA review on Shock tubes with multitudinous applications
2023, International Journal of Impact EngineeringCitation Excerpt :When the pressure exceeds 5.65 MPa, permanent deflection occurs in the form of bulging. The compressive strength also found to be decreasing with the increase in the test pressures [178]. Testing the composites in shock tube rather than testing it in live explosion was more economical, safe and reliable.
Controllable parameters as the essential components in the analysis, manufacturing and design of 3D woven composites
2022, Composites Science and TechnologyCitation Excerpt :A schematic of such reinforcement is shown in Fig. 1(a). There is a reasonable volume of published research addressing the transverse impact resistance of these materials, e.g. Refs. [5,9,10]. However, non-crimp composites are just one type of the woven composites.
Dynamic damage in FRPs: From low to high velocity
2022, Dynamic Deformation, Damage and Fracture in Composite Materials and Structures, Second Edition