Dynamic strength in oriented fiber glass composite shells

Abstract

624.074.4:678 Differences in chemical compositions and mechanical properties of fibers and different schemes of layer reinforcement of composite shells pose the problem of their optimal choice to ensure high specific strength under dynamic loading (such as for protective constructions of a single action) [1][2][3].The purpose of this paper is to study the dynamic response and the carrying capacity under the internal explosive loading of oriented fiberglass shells reinforced with roving strips based on VM-1, VMP, R and X fibers by the same scheme [VM-1, VMP are widely used fibers, R, and X are experimental fibers of special composition (developments by VNIISPV in Kryukov, Moscow region)]. Here, similar results obtained for Plexiglas shells based on SVM fibers are" presented for comparison.For comparing the calculated estimates of the resistance of the tested fibers to pulse action, the criterion 6 = cg suggested in [1] was used instead of the specific strength ap/p, where 6 is the limiting expansion rate of an annular element, c is the sound velocity in the fiber, and k" is the limiting stress strain. Previously the criterion was checked by comparing different load-carrying fibers in axisymmetric constructions made of composite materials, and for the explosive action the following proportion was established: 6 --~ ~ (~ = m/M is the ratio of the charge mass m of the explosive causing the initial stage of fracture on explosion to the shell mass M with internal radius R and length 4R) [1, 4].Some comparable data on mechanical properties, specific strength, and calculated values of 6 for the above fibers are listed in Table 1. In terms of the parameter 6, the VMP and VM-1 glass fibers R and X are slightly worse by factors of 1.3 and 1.4, respectively. Plexiglas fiber surpasses glass fibers in specific strength by a factor of more than 1.4.The test objects were cylindrical shells fabricated by combined winding of strips impregnated with an epoxy binder with the intercalation of double spiral layers (c 2 = 4-45 ~ and circumferential ones (~ = 90 ~ with a thickness ratio 1 : 1. The shells used in the experiments were composed of fiberglass and Plexiglas materials with internal radius R = 150 mm, length 4R, and relative wall thickness ~/R = 4.18-6% (fiberglass shells based on X fibers had $/R = 2.45-2.7 and Plexiglas shells had ~/R = 8.2-8.6%). Fiberglass and Plexiglas shells were reinforced with roving strips and fiber bundles, respectively:Type 1: VM-1 fiberglass, roving RVMN 10-1260-80 TU 6-11-370-75; Type 2: VMP fiberglass, roving RVMPN 10-1200-78 (a pilot batch); Type 3: R fiberglass, roving PPH 10-1400-78 (a pilot batch); Type 4: X fiberglass, roving PXH 9-925-78 (a pilot batch); Type 5: SVM Plexiglas (fiber), SVM fiber bundle 3-300-58,8 x 17-1000 TU 6-06-112-84. An epoxy binder (brand EDT-10, SST 3-4750-80) was used for all types of specimens. Dynamic loading of a shell open from the end faces was made by explosion at the geometric center of a spherical explosive charge of mass m made of trotyl-hexogen alloy (T...

Criterion for Selecting Composite Materials for Explosion Containment Structures (Review)

“…The experiments of [17] showed that the specific strength distribution according to the criterion ξ under explosive loading completely agrees with the order anticipated according to the criterion w for fibers. The highest specific load-bearing capacity is characteristic of VM-1 and VMP fiberglass shells, and the specific loadbearing capacity of R and Kh fiber shells is 25 and 45%, respectively, lower.…”

“…The results of similar tests of SHM organic plastic shells are also given in [17] for comparison. Cylindrical shells were formed by combined winding of tapes impregnated withÉDT-10 epoxy binder with alternation of double helical (ϕ 1 = ±45 • ) and hoop (ϕ 2 = 90 • ) layers at a layer thickness ratio of 1 : 1.…”

“…Results of two series of experiments with shells tested by explosion in a cavity filled with air are presented in [17]. The tests were performed with open cylindrical shells of various types and open cylindrical fiberglass shells in which steel shells (St. 20 steel) were inserted with a gap of not more than 0.2 mm, The steel shells had an inner diameter 2R 1 = 295 mm, a relative thickness δ 1 /R 1 = 1.4%, and a length 4R, and the thicknesses ratio of the shells was 0.2-0.3.…”

“…In [17], the dynamic response and load-bearing capacity was studied for internal explosive loading of shells of oriented fiberglass with identical reinforcement by tapes of VM-1, VMP, R, and Kh fiber rovings (VM-1-1 and VMP are widely used fibers and R and Kh are experimental fibers). The results of similar tests of SHM organic plastic shells are also given in [17] for comparison.…”

“…In [17], the dynamic strength criterion w was calculated not for fiber but for the hoop direction of the shell composite in order to enlarge the experimental data collection. Figure 1 compares the obtained values of w and the calculated specific load-bearing capacity ξ of the tested shells (the shells were filled with air and failed during the first extension because of an excess over the ultimate hoop strain of the composite ε el ).…”