SEVERANCE OF POLYCARBONATES AND POLYCARBONATE LAMINATES WITH LINEAR SHAPED CHARGE

Abstract: The present invention involves a method for severance of materials made of polycarbonate, polycarbonate laminate and acrylic/polycarbonate laminate, such as the materials from which many of today's military aircraft canopies are manufactured. A method of severing a section of an aircraft canopy so as to allow aircrew egress is necessary for aircrew safety. Past severance methods focused on fracturing materials using the shock waves created by explosive charges placed on, near or in the canopy material. These methods are effective for fracturing canopies manufactured from acrylic type materials, however, they are not reliable in severing polycarbonate type materials. The present invention utilizes a linear shaped explosive charge placed at a predetermined distance or stand off from the polycarbonate material to be severed. The coreload of the charge is determined such that the minimum coreload necessary to effect severance of a given thickness of polycarbonate material is utilized. A retainer is placed around the charge and affixed to the material such that the charge is at the proper stand off from the material. The retainer surrounds the back side of the charges but leaves open space between the charge and the material to be severed. Upon detonation, the charge creates an explosive cutting force, or jet blast, that severs the polycarbonate material. The present invention also involves methods for intersecting explosive charges about a pattern to be severed and methods for transferring detonation between such intersecting explosive charges.

Description: SEVERANCE OF POLYCARBONATES AND POLYCARBONATE LAMINATES WITH LINEAR SHAPED CHARGE FIELD OF THE INVENTION The present invention relates to seveπng materials, such as an aircraft canopy made from polycarbonate, polycarbonate laminate or acrylic/polycarbonate laminate, with an explosive charge BACKGROUND Most military aircraft contain an ejection seat that allows the pilot to escape the aircraft v. hile in flight. When an ejection seat is jettisoned from the cockpit of an aircraft, it must pass through the region occupied by the transparent canopy of the aircraft. In instances w here the canopy is not jettisoned pπor to the ejection seat firing, the ejection seat must be capable of blasting entirely through the canopy To reduce the πsks to the pilot or other aircraft occupant attendant to forcing the ejection seat through the canopy, canopy fracture systems have been provided to fracture the canopy ana better clear a path for the ejecting occupant so as to minimize bodily impact with the canopy Canopy fracture systems nave been effective at removing portions of canopies that are made from fragihzing matenals, such as cast or stretched acrylic. Fragihzing mateπals are those that may be caused to shatter into a significant number of pieces on application of sufficient pressure or explosive force. These systems utilize a mild detonating charge (MDC) or linear shaped charge (LSC) placed on, m or near the transparency which, upon detonation, creates shock waves that fracture the canopy. With fragihzing canopies, such as those made from cast or even stretched acrylic, it is not necessary to fully sever the material in order to defeat its structural integrity. Many high performance aircraft utilize polycarbonate in their canopies instead of acrylic. Polycarbonate is a nonfragilizing mateπal, meaning that it does not shatter on application of explosive force. With polycarbonate, it is absolutely necessary to fully sever the mateπal because fractuπng to complete the break is very unreliable. Because polycarbonate has a relatively low melt point and because cutting the mateπal generates considerable heat there also exists a potential for reseahng behind the cut if the severance is not complete. U S. Pat. No 5, 170,004 teaches an explosiv e device wherein a nearly incompressible transmitting medium is placed between the exϋlosive device and an aircraft canopy The function of the transmitting medium is to transmit the shock wave, produced upon detonation, to the canopy with a minimum of dissipation This device is effective on fragihzing canopies out has not been successful with thicker non-fragilizing canopies made from monolithic polycarbonate, polycarbonate laminates or acrylic/polycarbonate laminates U S Pat. No 5,780.763 teaches a method of fracture wherein explosive cords are placed in parallel grooves on the upper surface of a canopy and simultaneously detonated to create overlapping shock waves. This method is apparently capable of breaking a 75 inch thick polycarbonate m the laboratory at ambient temperature or below, but is unreliable at elevated temperatures on the order of 165" Fahrenheit or aoove. This method, however, requires two charges, grooves to be cut in the mateπal and also utilizes shock waves which are not reliable on polycarbonate materials. U.S. Pat. No. 5,954,296 also relates to an aircraft canopy fracture system. The 296 patent claims a canopy with a severable region shaped so as to inhibit passage of the severable region back through the canopy after severance. The 296 patent also refers to the use of a LSC to sever a polycarbonate canopy. All documents, including other patents and references, referred to in this document are hereby incorporated by reference in their entirety, although no αocuments are admitted to render any of the claims unpatentable either alone or in combination with any other references known by the applicant The pπor art also does not adequately deal with the problems of providing for severance around the comers of the severable poπion of the target or for routing a charge over the top ot another cnarge It is therefore an object of this invention to prov ide a severance method which severs mateπals such as polycarbonate, polycarbonate laminates or acn lic/polycarbonate laminates that cannot be severeα bv existing methods except by use of excessiv e amounts of explosive charge or by placing the charge inside the mateπal to be fractured, thereoy degrading the mateπal's structural integπty It is another object of this inv ention to prov ide a se erance method that allow s for a minimum amount of explosive charge to se er a giv en thickness of mateπal at high and low temperature extremes It is further an object of this invention to provide a sev erance method that allows for severance around comers and through intersecting portions of the explosive charge SUMMARY OF THE INVENTION The present invention is a method for seveπng a non-fragi zing mateπal such as polycarbonate w ith a linear shaped charge ("LSC") Previous methods of polycarbonate, polycarbonate laminate or acrylic/polycarbonate laminate severance were either ineffective, or required imbedding explosive charges into the canopy itself. The pπor art relies on the use of shock waves to fracture aircraft canopies. These methods, however, are not effective or reliable on canopies made from non-fragilizing mateπals such as polycarbonate, polycarbonate laminate or acrylic/polycarbonate laminate The present invention discloses a method of using the cutting face of the explosive charges to sever a mateπal such as polycarbonate, instead of relying on unreliable shock waves Because the severance method of this invention is more effective and more reliable than previous severance methods, a lesser amount of explosive charge is required to effect target sev erance In the case of a polycarbonate aircraft canoDy target, the present i"' ention s severance method provides pilots with a low er exposure to explosion back blast ana noise An LSC is placed in proximitv to the mateπal to be sev ered at a distance sufficient to ge n erate an explosi e cutting face or "jet" adequate for cutting the target thickness The LSC is ne.d in place and at the sufficient distance by a retainer that surrounds the back of the charge Tr.e retainer is adhered or attached to the target, again maintaining the appropπate distance be π v een the charge and the target Upon detonation the charge sev ers the target The charge ana retainer may be tooled to provide for effective severance with minimum explosive force a-ound comers The present invention also provides for vaπous methods of charge intersection, crosso er and detonation transfer BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of an explosive charge of the present invention attached to a target tr.at is to be severeα Figure 2 is a side view of an explosive charge of the present invention after detonation sevenng the target mateπal Figures 3a-d are tables showing performance test results of varying gram sizes of various LSCs on polycarbonates of varying thickness. Figure 4 is a depiction of a polycarbonate laminate and its target thickness. Figure 5 is a depiction of a severance pattern disclosed in U.S. Pat. No. 5,954,296. Figure 6 is a depiction of the crossover method of laying one LSC over another. Figure 6a is a depiction of a side view of the crossover method. Figure 6b is a depiction of a side view of the crossover method where a portion of the sheathing on the low er length of LSC has been cut a ay. Figure 6c is a depiction of a side view of the crossover method where a solid anvil is placed under the low er length of LSC to aid in detonation transfer. Figure 7 is a αepiction of tne invention's method of piggy -backing where one LSC comes up over a low er piece of LSC ana πdes the same line of severance for a given distance. Figure 7a is a side view of the piggyback method Figure 8 is a depiction of the mitered jomt method with four intersecting pieces of LSC. Figure Sa is a side view of the miter method Figure 9 is a depiction of the miter method joining two lengths of LSC at a πght angle. Figure 9a is side view of the miter method used at a πght angle. Figure 10 is a depiction of transferring LSC detonation through a crossover or intersection in the LSC utilizing a booster charge. Figure 10a is a depiction of transferring LSC detonation through a crossover or intersection in the LSC utilizing an explosive transfer charge encased in a manifold. DETAILED DESCRIPTION Referring to the drawings by reference numbers, Fig. 1 shows a linear shaped charge ("LSC") 10 of the present invention in position on the target. The LSC is of a strength sufficient to sever a target, such as an aircraft canopy transparency, made from polycarbonate, polycarbonate laminate or acrylic/polycarbonate laminate. The LSC 10 includes an explosive core 1 1 and a sheath 12 The best results are obtained when the LSC is shaped like a chevron with the opening facing and parallel to the target 13 There is open space between the LSC and the target The LSC is surrounded by a retainer 14 that is attached to the target bv some form of adhesiv e The retainer attaches the LSC to the target such that the LSC is offset from the target by a distance 15 that allows the LSC to generate an εxplosiv e blast of sufficient strength to sev εr the target Figure 2 show s the present inv ention at the moment of explosion sev eπng a target In a preferred embodiment the retainer is made from rubber and attached to the canopv with an epoxy or other adhesiv e The retainer not only serves to hold the LSC in place at an approoπate distance from the canopy, it also acts to attenuate the back blast and noise from the explosion to protect the aircrew (in the case of a canopy target) Tne retainer may also be made from a other type rubber products, an epoxv composite or other compounds and stiU- achieve satisfactory results LSC sheathing is maαe of metal, typically tin, lead, aluminum, silver or copper For severance of polycarbonates, tin, lead and silver are preferable, but silver is rarely used due to high mateπal costs Testing was performed using PBXN-5/Lead, PBXN-5/Tιn, HNS/Leaα and HNS/Tin LSC of varying coreloads Some of those test results are set forth in Figure 3 This testing revealed that a lead sheath is slightly more effective for seveπng polycarbonates than a tin sheath. Both are effective, however, and because of the hazards of working with lead, a tin sheath is the preferred embodiment. A tin sheath is slightly more effective than a lead sheath m seveπng aluminum Testing also determined that PBXN-5 powder is supeπor to HNS powder Because of the lack of success with previous canopy fractuπng and severance methods in polycarbonate canopies, a great deal of testing was performed to determine the proper LSC coreload and stand off necessary to sever a set thickness of polycarbonate In the present invention the coreload and stand-off necessary to sever polycarbonates of varying thickness is disclosed As vv ould be expected, the thicker the polycarbonate to be severed the greater the coreload requireα The LSC is more effective if setoff a certain distance from the target A tabular representation of the test results achieved on varvmg polvcarbonate thicknesses with arying LSC core.oaα, powder sheathing back ups ana stand-off is set forth below IDENTIFICATION TEST fl SOURCE JNFORMATION NOTES Back Up Thickness Penetrati 1 UDRI Dow-Cahbre 300 6, 3/4", #4 12 gr/fl HNS/Lead, RTV, No Stand Off(SO), Parallel Beam, Broke retainer 0 75 .045/bro 2 UDRI Dow-Cahbre 300-6, 3/4", #2 20 gr/fl RDX/Lead, RTV, No SO, Parrallel Beam, Broke retainer 0.75 bro 3 UDRI Dow-Cahbre 300-6, 3/4", #9 12 gr/ft HNS/Lead, RTV, No SO, Bottom Clamped, 05 Imp , B-U retainer 0.75 0 4 UDRI Dow-Cahbre 300-6, 3/4", #12 21 gr/ft CH6/AI, 0 090 SO, 0 275 Penetration, Cracked Through TMD 0.75 .15/bre 5 UDRI Dow-Cahbre 300-6, 3/4", #14 21 gr/ft CH6/AI, No SO, 0 180 Penetration, Some cracking TMD 0.75 .180/bre 6 UDRI Dow-Calibre 300-6, 3/4", #15 21 gr/ft CH6/AI, No SO, RTV filled, Little Penetration TMD 0.75 0 0 8 UDRI Dow-Cahbre 300-6, 3/4", #3 40 gr/fl PBXN5/I_ead, 180 SO, inside radius-straight, cut rubber 0.075 bro 33 Texstar Coated In C678, Out C992, 5/16" 12 gr/fl, HNS/Tin, 0 125 SO, some pen, all melted, no cut rubber 0.312 0. 00 34 Texstar Coated In C678, Out C992, 5/16" 12 gr/ft, PBXN-5/Tιn, 0 160 SO, Cut rubber 0.312 c 35 Texstar Coated In C678, Out C992, 5/16" 12 gr/ft, PBXN 5/Tιn. 1 G0 SO, 90" Angle. Cut except angle paper 0 312 0 36 Texstar Coated In C678, Out C992, 5/16" 12 gr/ft, PBXN-5/Tιn, 160 SO, unrestrained, Cut paper 0.312 c 37 Texstar Coated In C678, Out C992, 5/16" 12 gr/ft, HNS/Tin, 0 125 SO, Unrestrained, Cut paper 0.312 C 38 Texstar Coated In C678, Out C992, 5/16" 15 gr/ft, HNS/Tin, 0 125 SO, cut rubber 0.312 c 39 Texstar Coated In C678, Out C992, 5/16" 12 gr/ft PBXN5/Tιn, 360° sep test, cut & broke rubber 0.323 49 Texstar Coated In C678, Out C992, 3/ ]' 12 gr/ft, PBXN-5/Tιn, 0 160 SO, Nearly Severed paper 0.375 0. 50 Texslar Coated In C678, Out C992, 3/8" 12 gr/fl, HNS/Tin, 0 125 SO, cut rubber 0.375 c 51 Texstar Coated In C678, Out C992, 3/8" 15 gr/ft, HNS/Tin, 0 125 SO, cut rubber 0.375 c 52 Texstar Coaled In C678, Out C992, 3/8" 12 gr/ft, PBXN5/Tin, 0.130 SO, remelted+D73 rubber 0.375 c 53 Texstar Coated In C678, Out C992, 3/8" 12 gr/ft, HNS/Lead, 0.130 SO, remelled rubber 0.375 c 15 gr/ft, PBXN5/Tin, .15 SO, 360° 2" R Bend - sep. test, cut except 54 Texstar Coated In C678, Out C992, 3/8" joint rubber 0.375 not joi 65 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN-5/Tin, 0.160 SO, some penetration, mostly melted paper 0.5 0.3 66 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN-5/Lead, 0.160 SO, melted but not severed paper 0.5 0.4 67 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN-5/Lead, 0.160 SO, unrestrained, some pen, melted paper 0.5 0.4 68 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN-5/Tin, 0.160 SO, unrestrained paper 0.5 0.44 69 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN5/I_ead, 90 deg bend, 0.150 SO, close paper 0.5 cut not ben 70 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN5/Tin, 90 deg bend, 0.150 SO, shattering, close paper 0.5 cut .3 V© 71 Texstar Coated In C678, Out C992, 1/2" 15 gr/fl, PBXN5/Lead, 200 deg F, 0.150 SO, remelted rubber 0.5 cut/remelte 72 Texstar Coated In C678, Out C992, 1/2 " 15 gr/ft, PBXN5/Tin, 200 deg F, 0.150 SO, unteth, hanging thread paper ? 0.5 c 73 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN5/Lead, -65° F, 0 150 SO, cut rubber 0.5 c 74 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN5/Tin, -65° F. 0.150 SO, cut rubber 0.5 X 75 Texstar Coated In C678, Out C992, 1/2" 20 gr/ft, PBXN-5/Lead, untelh, cut rubber 0.5 c 76 Texstar Coated In C678, Out C992, 1/2" 20 gr/ft, PBXN-5/Tiπ. unteth, cut rubber 0.5 c 77 Texstar Coated In C678, Out C992, 1/3" 20 gr/ft, PBXN-5/Tin, unteth, some penetration, S curve, not cut rubber 0.5 cut/.4 78 20 gr/fl, PBXN-5/Lead..145 SO, "S" turn, not cut in bends rubber 0.55 cut/,4 79 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN-5/Tin, 90° turn, 0.145 SO, restrained, 2" radius rubber 0.5 0.3 80 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN-5/Lead, 90° turn, 0 145 SO, restrained, 2" radius rubber 0.5 cut/99 81 Texstar Coated In C678, Out C992, 3/4" 30 gr/fl, PBXN-5/Lead, unrestrained, 175 SO.cut paper 0 75 c 82 Texstar Coated In C678, Out C992, 3/4" 30 gr/ft, PBXN-5/Tin, unrestrained, 175 SO, 540 pen, cracked paper 0.75 0. 83 Texstar Coated In C678, Out C992, 3/4" 30 gr/ft. HNS/Lead, 0 150 SO, 480 pen, some cracking paper 0.75 0.4 84 Texstar Coated In C678, Out C992, 3/4" 30 gr/ft, HNS/Tin, 0 120 SO, unteth, 440 pen rubber 0.75 0 4 85 Texstar Coated In C678, Out C992, 3/4" 30 gr/ft, PBXN5/Lead, 0 150 SO, -70° F, Cut rubber 0.75 c 86 Texstar Coated In C678, Out C992, 3/4" 30 gr/ft, PBXN5/Lead, 0 150 SO, 200° F, untethered, cut rubber 0.75 c 87 Texstar Coated In C678, Out C992, 3/4" 30 gr/ft, PBXN5/Lead, 0 182 SO, 200° F, restrained, cut rubber 0.75 c 88 Texstar Coated In C678, Out C992, 3/4" 30 gr/lt, PBXN5/Lead, 0 182 SO, 200° F, unrestπned, cut rubber 0.75 c 105 NSWC MX2054 920415, 0 500 530 thick, 15 gr/ft PDXN5/1 e.ul, 1 0 SO, No_ιr ly severed rubber 0.53 0. 106 NSWC MX2054-920415, 0 500 530 thick, 20 gr/ft PBXN5/I_ead, 150 SO, 90° bend, cut rubber 0.53 c 109 Pilkington 0 250 X 36 X 60 12 gr/ft, 815525-2 (Mm/Max), RTV, No SO, No Cut, cracked thru no SO 0.25 0.1 1 10 Pilkington 0 250 X 36 X 60 12 gr/ft, 815525-2 (Mm/Max), RTV, No SO, Scored, cut & melted no SO 0.25 cut/melte 111 Pilkington 0 250 X 36 X 60 12 gr/fl, 815525-2 (Mm/Max), No SO, No cut no SO 0 25 . 05/cracki 112 Pilkington 0 250 X 36 X 60 12 gr/ft, 815525-2 (Mm/Max), No SO, No cut no SO 0.25 .04/melli 113 Pilkington 0 250 X 36 X 60 12 gr/ft, 815525-2 (Mm/Max), 0 1 10 SO, Use CH 825252, Cut rubber 0 25 c 114 Pilkington 0 250 X 36 X 60 12 gr/ft, 815525-2 (Mm/Max), 0 1 10 SO, Use CH 825252, Cut rubber 0.25 c 116 Pilkington 0 250 X 36 X 60 12 gr/ft, HNS/Tin, 0 1 10 SO, Use CH 825252, Cut paper 0.25 c 118 Pilkington 0250X36X60 12 gr/ft. PBXN-5/Tιn, 0110 SO, Use CH 825252(7), Cut paper 025 c 119 Pilkington 0250X36X60 12 gr/ft, HNS/Lead, 0110 SO, 200° F, Cut rubber 0.25 c 120 Pilkington 0250X36X60 12 gr/ft, HNS/Lead, 0110 SO, RTV Filled, Poor Performance rubber 0.25 00 125 Pilkington 0312X36X60 12 gr/ft, HNS/Lead, 0110 SO, No Cut rubber 0.312 .28/p 126 Pilkington 0312X36X60 12 gr/ft, HNS/Lead, 0145 SO, No Cut rubber 0.312 0. 127 Pilkington 0312X36X60 15 gr/ft, HNS/Lead, 0145 S O ,Cut rubber 0.312 c 128 Pilkington 0.312X36X60 15 gr/ft, PBXN-5/Lead, 0145 S O , Cut rubber 0.312 c 129 Pilkington 0312X36X60 12 gr/ft, PBXN-5/Tιn, 0110 SO, Use CH 825252, Cut but Remelted paper 0.312 c 141 Pilkington 0350X36X60 15 gr/ft, HNS/Lead, 0145 S O , Cut rubber 0.35 c 142 Pilkington 0350X36X60 15 gr/ft, PBXN-5/Lead, 0145 S O , Cut rubber 0.35 c 143 Pilkington 0350X36X60 15 gr/ft, PBXN-5Tιn, 0145 S O , Cut paper 0.35 c 167 Texstars 0310 Ply Laminate 12 gr/ft PBXN5mn, 15 SO, Gap Test, Gap did not break rubber 0312 cut/not j 173 Sierracm 0375 Ply Laminate 15 gr/ft HNS/Lead, 0145 SO, Cut rubber 0.375 « 174 Sierracin 0375 Ply Laminate 15 gr/ft PBXN-5/Lead, 0145 SO, Cut rubber 0.375 c 175 Sierracin 0375 Ply Laminate 15 gr/ft PBXN-5π * ιn, 0145 SO, Cut paper 0.375 c 176 Texstars 0375 Ply Laminate 12 gr/ft PBXN5/Tιn, 070 SO, Untethered, butted joint, cut, not joint rubber 0.375 cut/not j 177 Sierracin 0375 Ply Laminate 12 gr/ft, PBXN-5fT in, 0070 SO, Cut j oint rubber 0.375 cut joi 178 Sierracin 0375 Ply Laminate 12 gr/ft, PBXN-5/Tιn, 0150 SO, cut 1 end, 235 pen other end rubber 0.375 0.30 181 Sierracin 0 500 Ply Laminate 15 gr/ft HNS/Lead, 0 145 SO, No Cut, 310 Penetration rubber 0 5 0 182 Sierracin 0 500 Ply Laminate 15 gr/ft PBXN-5/Lead, 0 145 SO, Cut rubber 0 5 183 Sierracin 0 500 Ply Laminate 20 gr/ft HNS/Lead, 0 145 SO, No Cut, 450 Penetration rubber 0.5 0. 184 Sierracin 0 500 Ply Laminate 20 gr/ft PBXN-5/Lead, 0 145 SO, Cut rubber 0 5 c 185 Sierracin 0 500 Ply Laminate 15 gr/ft PBXN-5/Lead, 0 145 SO, Cut but remelted rubber 0 5 c 186 Sierracin 0 500 Ply Laminate 15 gr/ft PBXN-5/Lead, 0 145 SO, 200° F, Cut rubber 0 5 c 187 Sierracin 0 500 Ply Laminate 15 gr/ft PBXN-5/Lead, 0 145 SO, G5° F, Cut rubber 0 5 c 188 Sierracin 0 500 Ply Laminate 15 gr/ft PBXN-5/Tιn, 0 145 SO, Cut but remelted paper 0 5 c 189 Sierracin 0 750 Ply Laminate 25 gr/ft HNS/Lead, 0 145 SO, No Cut, -0 420 Penetration rubber 0 75 0 . 190 Sierracin 0 750 Ply Laminate 30 gr/ft HNS/Lead, 0 145 SO, No Cut, -0 450 Penetration paper 0.75 0 191 Sierracin 0 750 Ply Laminate 20 gr/ft PBXN-5/Lead, 0 145 SO, No Cut, -0 450 Penetration rubber 0 75 0 192 Sierracin 0 750 Ply Laminate 25 gr/ft PBXN-5/Lead, 0 145 SO, No Cut, - 0 550 Penetration rubber 0 75 0 193 Sierracin 0 750 Ply Laminate 30 gr/ft PBXN-5/Lead, 0 165 SO, Cut paper 0.75 C 194 Sierracin 0 750 Ply Laminate 30 gr/ft PBXN-5/Tιn, 0 145 SO, No Cut, -0 550 Penetration paper 0.75 0 195 Sierracin 0 750 Ply Laminate 15 gr/ft PBXN-5/Lead, 0 145 SO, -0 440 Penetration paper 0 75 0 196 Sierracin 0.750 Ply Laminate 30 gr/ft PBXN 5/Lead, 0 165 SO, Cut Partially paper 0 75 0 197 NSWC-IH 0 500 D910108-06 15 gr/fl PBXN-5/Lead, 0 145 SO, 90deg, 1 of 90 * s not cut none 0 5 0 4 198 NSWC-IH 0 500 D910108-06 15 gr/ft PBXN-5/Tιn, 0 145 SO, 90dog. some pen not cut none 0.5 0. 199 NSWC-IH 0 500 15 gr/ft PBXN-5/Tιn, 0 145 SO, some pen, all melted, no cut paper 0.5 0 4 200 NSWC-IH 0 500, 15 gr/ft, PBXN-5/Lead, 0 145 SO, remelted 0 5 46/cu 205 Sierracin 0 750 30 gr/ft PBXN-5/Tιn, 0 275 SO, - 550 Pen , Crack & Melt , No Cut paper 0 75 0 5 206 Sierracin 0 750 30 gr/ft, PBXN-5/Lead, 0 250 SO, - G50 to Cut, No Sep. remelted paper 0.75 .675/cut 207 WPAFB 0 750 40 gr/ft, HNS/Lead, 0 150 SO, cut, unrestrained rubber 0 75 cut 208 WPAFB 0 750 40 gr/ft HNS/Tin, 0 190 SO, 480 pen, unrestrained rubber 0 75 0 4b 209 WPAFB 0 750 40 qr/ft, PBXN5/I ead, 0 200 SO, cut unrestrained rubber 0 75 cut 210 WPAFB 0 750 40 gr/ft, PBXN5f. ιn, 0 230 SO, cut, unrestrained rubber 0 75 cut 213 Texstar Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN5/Lead, 90 deg bend 0 150 SO, cut/0 48 penetration paper/- 0 53 48/cut > 214 Texstars Coated In C678, Out C992, 1/2" 25 gr/ft, HNS/Tin, 0 150 SO, restrained, -65° F, cut rubber 0 54 cu 215 Texstars Coated In C678, Out C992, 1/2" 25 gr/ft HNS/Tin. 0 150 SO, Broke 0 475 Pen rubber 0 54 0 475 216 Texstars Coated In C678, Out C992, 1/2" 15 gr/ft. PBXN5/1 ead, 0 150 SO, 200° F, Unrestπned. Cut rubber 0 54 cut 217 Texstars Coated In C678, Out C992, 1/2" 15 gr/ft, PBXN5/Lead, 0 150 SO, restrained , cut rubber 0 54 0 51 218 Navy 1/2", MX2054-920415 20 gr/ft PBXN5/Tιn, 0 185 SO, 90° bend, 2" R, untethered, cut rubber 0.5 cut 220 Texstars 1/2", Coated In C678, Out C992 17 5 gr/ft PBXN5/Tιn, 185 SO, 90° bend, 2" R, not cut rubber 0 53 0.22 221 Texstars 0 740 Laminated, special 40 gr/ft PBXN5/Lead, 0 200 SO, Cut rubber 0.74 cut ??2 Sierracin 0 500 Inch 20 gr/ft PBXN5/Lead, 0 15 SO, 90° bend, ?" R, 200° F, cut rubber 0 5 cut 223 Sierracin 0 500 Inch 20 gr/ft PBXN5/Lead, 0 15 SO, 90° bend, 2" R, -65° F rubber 0.5 cut 224 Sierracin 0 500 Inch 15 gr/ll PBXN5/1 ead, 0 15 SO, untethered, cut rubber 0 5 c 225 Sierracin 0 500 Inch 15 gr/lt PBXN5/Lead, 0 15 SO, tethered, cut rubber 0 5 c 226 Sierracin 0 75 inch 30 gr/ft PBXN5/Lead, 0 15 SO, cut rubber 0 75 c 15 gr/ft PBXN5/Lead, 0 15 SO, 1/2" RTV filled Apex, not cut in RTV 228 Texstars 0 50 inch area rubber 0 5 not RT 231 UDRI 0 75 inch 12 gr/ft PBXN5/Tιn, 0 100 SO, 205 pen rubber 0.765 0 28 232 UDRI 0 75 inch 15 gr/ft PBXN5/Tιn, 0 100 SO, 36 pen rubber 0 765 0 3 233 UDRI 0 75 inch 15 gr/ft PBXN5/Lead, 0 100 SO, 33 pen rubber 0 765 0.3 17 5 gr/ft PBXN5/Tιn, 100 SO, HMR-T98-1321 , 320 pen, cracking 234 UDRI 0 75 inch thru rubber 0.765 0.3 235 UDRI 0 75 inch 17 5 gr/ft PBXN5π ~ ιn, 100 SO, LMR-T98-1323, 32 pen rubber 0.765 0 3 236 UDRI 0 75 inch 17 5 gr/ft PBXN5/Lead, 1 10 SO, HMR-T98-1322, 30 pen rubber 0 765 0 237 UDRI 0 75 inch 17 5 gr/ft PBXN5/Lead, 1 10 SO, LMR-T98-1320, 31 pen rubber 0 765 0 3 238 UDRI 0 75 inch 20 gr/ft PBXN5/Tιn, 0 150 SO, 57 pen rubber 0.765 0.5 239 UDRI 0 75 inch 20 gr/ft PBXN5/Lead, 0 110 SO, 4 pen rubber 0.765 o. 240 UDRI 0 75 inch 22 5 gr/ft PBXN5/Tιn, 110 SO, HMR-T98-1321 , 48 pen rubber 0.765 0 4 22 5 gr/ft PBXN5/Tιn, 1 10 SO, LMR-T98-1323, 45 pen, 99% 241 UDRI 0 75 inch broken rubber 0.765 0.4 242 UDRI 0 75 inch 22 5 gr/ft PBXN5/Lead, 150 SO, I IMR-T98-1322, 58 pen rubber 0.765 0.5 243 UDRI 0 75 inch 22 5 gr/ft PBXN5/Lead, 100 SO, LMR-T98-1320, .37 pen rubber 0.765 0.3 244 UDRI 0 75 inch 25 gr/ft PBXN-5Λ ~ ιn, 0 190 SO, 6 pen, cut rubber 0.765 cu 245 UDRI 0 75 inch 25 gr/fl PBXN-5/Lead, 0 190 SO, 0 pen rubber 0.765 0 246 UDRI 0 75 inch 30 gr/ft PBXN5/Tιπ, 0 190 SO, 60 pen, cut rubber 0.765 c 247 UDRI 0 75 inch 30 gr/ft PBXN5/Lead, 0 150 SO, 0 69 pen rubber 0.765 0 248 UDRI 0 75 inch 40 gr/ft PBXNS/Tm, 0 200 SO, cut rubber 0.765 c 249 UDRI 0 75 inch 40 gr/ft PBXN5/Lead, 0 200 SO, Cut rubber 0.765 c 250 Navy D910108-08 20 gr/fl PBXN5/Lead, 0 150 SO, 1/2" RTV Block, no cut undei RTV rruubbbbeerr 0.53 0. 251 Texstars 0 375 inch 15 gr/ft PBXN5 Tιn, 0 15 SO, 360° turn butt up with angle cut rubber 0.375 not at joi 252 Texstars 0 375 inch 15 gr/ft PBXN5/Tin, 0 15 SO, 360° turn with overlap rubber 0.375 c 253 0 75 inch 25 gr/ft PBXN5ATιn, 0 190 SO, partial cut then broke rubber 0.75 c tΛ 254 0 75 inch 30 gr/ft PBXN5/Tιn, 0 190 SO, bent 120° but hanging rubber 0.75 c 40 gr/ft PBXN5/Tin, 0 200 SO, 360° turn with overlap, broke, but not 255 0 75 inch a niceclean cut rubber 0.75 c 15 gr/ft PBXN5ATιn, 150 SO, 3G0° turn with overlap, 0 40 pen, cut 256 Navy D910108 08 overlap Isc oft rubboi 0 53 0 20 gr/ft PBXN5/Lend, 180 SO, 3(50" turn with overlap, some pen 257 Navy D910108-08 But most 0.40 + rubber 0 53 25 gr/ft PBXN5/Lead, 180 SO, 360° turn with overlap, mostly cut ° 258 Navy D910108-08 except overlap rubber 0 53 c 15 gr/ft PBXN5/Tιn, 150 SO, 360° turn with overlap, broke but only 259 Navy D910108-08 0 37 pen rubber 0.53 0. 15 gr/ft PBXN5fTin, 150 SO, 360° turn with piggyback overlap, 36 260 Navy D910108-08 pen rubber 0.53 0. 20 gr/ft PBXN5/Lead, 150 SO, 360° turn with piggyback overlap , 261 Navy D910108-08 did not cut overlap rubber 0.53 cut/not ov 25 gr/ft PBXN5/Lead, 150 SO, 360° turn with piggyback overlap, 262 Navy D910108-08 did not cut overlap rubber 0.53 cut/not ov 20 gr/ft PBXN5/Tιn, Cross over, 150 SO, cut bottom LSC without 263 Navy D910108-08 detonating rubber 0.53 cut/not ov 264 500 inch 15 gr/ft PBXN5/Tιn, loop with mitercd joint, 150 SO, did not cut rubber 0.5 0. 265 .500 inch 15 gr/ft PBXN 5/Tιn, loop with mitered joint, .150 SO, did not cut rubber 0.5 0. 25 gr/ft PBXN5/Tin, "D" shape with mitered corners, 150 SO, Cut 266 .500 inch nicely rubber 0.5 cu 270 Sierracin 1 00 inch. 7 ply laminate 40 gr/ft PBXN5 Tιn, 90° mitered angle, 180 SO, cut nicely rubber 1 cu 271 Texstars .375 Coated 12 gr/ft PBXN5/Tιn, 0 070 SO, 300 pen rubber 0.375 0. 272 Sierracin 500 Laminated 12 gr/fl PBXN 5/Tιn, 070 SO, cut rubber 0 5 cu 273 Sierracin 500 Laminated 15 gr/ft PBXN5/Tιn, 070 SO, 360 pen rubber 0 5 0.3 274 Navy 500 cast 25 gr/ft PBXN5fTιn, 150 SO, "O" with T Mitered, Cut rubber 0.5 cu ON 278 Sierracin Laminated 448 12 gr/ft PBXN5/Tιn, 070 SO, 90° bend, cut rubber 0.448 c 279 Sierracin 448 Laminated 12 gr/ft PBXN5/Tιn. 070 SO, 90° bend, cut rubber 0.448 cu 280 Sierracin .525 Laminated 15 gr/ft PBXN5/Tιn, .150 SO, 90° bend, nearly completely severed rubber 0.525 99% c 281 Sierracin .525 Laminated 12 gr/ft PBXN5/Tin, 150 SO, 200° F, 90° bend, did not cut rubber 0.525 0.3' 282 Sierracin .525 Laminated 15 gr/ft PBXN5/Tιn, 150 SO, 200° F, 90° bend, cut rubber 0.525 c 283 Sierracin .448 Laminated 12 gr/ft PBXN5/Tιn, 070 SO, 200° F, 90° bend, cut rubber 0.448 c Previous methods of aircraft canopy fracturing and severance relied on the use of shock waves generated from an explosive charge In order to facilitate shock wave transfer from the explosive charge to the target, U S Patent No 5,170,004 taught the use of a nearly incompressible medium placed between the charge and target While this method is effective on acrylic and other fragihzing type mateπals, it is not reliable with polycarbonate, polycarbonate laminate or acrylic/polycarbonate laminates With polycarbonate type mateπals, the use of a incompressible or other medium between the LSC and the target degrades rather than improves results This is because polycarbonates are not easilv fractured and therefore cutting using the explosive jet" blast of the LSC is preferaole to fractuπng using shock waves Because severance is preferable to fractuπng, it is important that the area between the LSC and the target be clear of debπs This goes against the teacning of the 004 patent which taught the use of some form of nearly incompressible medium between the charge and the target in order to facilitate transmission of shock waves U S Pat No 5,780,763 taught a method of fracture wherein explosive charges are placed in parallel grooves cut in the upper surface of tne matenal and simultaneously detonated to create overlapping shock waves Again, because this method relies on shock waves which are unreliable to sever polycarbonate mateπals it is infeπor to the present invention that-uses the unimpeded explosive "jet" blast of the LSC to sever the mateπal .s revealed by the test results set forth above, the best severance results are obtained bv use of a rubber back up, a PBXN-5 powder and a lead or tin sheath Ideal set off was in the range of 0 100 to 0 300 inch for coreloads of 12 to 40 grams per foot Laminates of polycarbonate, acrylic, stretched acrylic and polyurethane can be severed with less overall energy than pure polycarbonate The target thickness for the laminate is the total thickness from the LSC side through the final layer of polycarbonate or polyurethane. Figure 4 shows the target thickness of a laminate. .Any acrylic outside the final polycarbonate or polyurethane layer is easily shattered by the shock wave created by the LSC seveπng the polycarbonate. Acrylic layers between the LSC and the final layer or polycarbonate or polyurethane will act very much like the polycarbonate for the entire thickness. Another shortcoming in the pπor art was difficulty in safely seveπng polycarbonates and other mateπals around corners. To create a passageway for an ejecting or egressing aircrew it is necessary that the LSC circumscπbe some pattern sufficient to allow egress Severance problems aπse w hen the LSC is bent around the comers of this pattern These problems are attπbutable to at least two factors First, in bending the LSC the coreload may be disbursed to less than an optimum strength, especially on the outside of the bend. Second, when the LSC ana its retainer are bent around corners, the open end of the chevron may be shifted from parallel to the target surface Optimal results are achieved w hen the open end of the chevron is parallel to the target surface and the explosive force is therefore perpendicular to that surface. Any alteration from parallel lessens the explosive force stπking the target and impedes severance Therefore, in a preferred embodiment of this invention, bends in the LSC are gentle, with turn radii kept on the order of 2 inches or above In this way the coreload of the LSC is kept consistent Additionally, both the LSC and its retainer are tooled so as to keep the open end of the LSC chevron parallel to, and the apex of the cnevron and resulting explosive force perpendicular to, the target Through these methods, the full force of the explosive charge is expended directly on and perpendicular to the target This allows severance with a minimum of coreload, thereby reducing noise and back blast The LSC must be placed on the target in a pattern that will effect severance of a portion of the target. In the pπor art the LSC was not able to crossover another length of LSC. Instead the LSC would be bent around as it approached another length of LSC. Figure 6 is a depiction of a LSC pattern on the severable portion of an aircraft canopy, as disclosed in the 296 patent discussed above In Figure 5 it can be seen that the charges must turn at sharp bends where it would be simpler, require less LSC and tooling, and avoid the degradation in performance associated with sharp bends if a length of LSC could simply intersect or crossover another length This inv ention effects such intersections and crossovers in several ways Figure 6 dεmcts one crossover method A first length of LSC 20 is first run along the target A second length of LSC 21, intersecting the first length, can then be run over the top of the first length When a crossover method is utilized the seconα length of LSC must be detonated before the first If the first length of LSC is detonated before the second length it will blow the second length off the target and greatly impede the severance capability of the second length of LSC Additionally, the crossover must be designed so that upon detonation, the second length of LSC detonates the first length of LSC If the second length of LSC merely severs the first length, without detonating it, the seveπng capability of the LSC will be again greatly reduced Figure 6a snows the second length of LSC 21 flattened ov er the first length of LSC 20 By flattening the second length of LSC 21 its cutting force is reαuced and it will detonate, instead of sever, tr.e first length of LSC 20 It mav also be desirable to cut away some of the metal sheathing on the top of the first length of LSC to assist detonation by reducing the amount of metal sheathing that the second length of LSC must to detonate through in order to detonate the first length of LSC Figure 6b shows the crossover method herein the first length of LSC 20 has part of its metal sheathing cut away 22 to facilitate its detonation by the second length of LSC 21 This may be especially important in higher coreload mateπal Another method of ensuπng detonation of the first length of LSC bv the second length is to insert a solid mateπal under the first length of LSC so that upon detonation of the second length of LSC the first length is forced against the solid mateπal to assist in detonation transfer Figure 6c shows a solid anvil type object 22 placed under the first length of LSC 20 The anvil adds reliability to the detonation transfer, especially with higher coreload LSC severance A variation on the crossover method is shown in Figure 7 In this method the second length of LSC 21 comes up on the first length of LSC 20 and πdes the same line of severance for some given distance This crossover method (referred to as a piggyback) not onlv avoids the snarp bend problem, it can also be used to add to the cutting capability of tne first length of LSC and should be considered in areas of the target mateπal that are thicker than other areas In the piggyback method it is also important to fire the second length of LSC first Fiπng the first length (the length closest to the target) first could result in blowing the second length off the target Figure 7a shows a side iew of the piggy back method An additional method of routing LSC through intersections in a pattern is the mitered loint Figure 8 shows a four wav mitered joint The LSC is cut on the appropπate angle (I e 45°) to meet with another end of LSC that is similarly mitered The joint is then joined with an adhesive Appropπate adhesives include C-7/W and 5-mιnute epoxy Figure 8a depicts a crossview of the four way mitered jomt Figure 9 shows a method of joining two lengths of LSC at a πght angle As with the crossover method, if one mitered joint is to πde over another it is important that the LSC closest to the target is not detonated until after the otner length of LSC Figure 10 shows another method of LSC intersection In Figure 10, a booster charge 30 is placed at the intersection of the adjoining lengths of LSC. The lengths of LSC abut to the booster charge that transfers detonation through the intersection While booster charges have been used to transfer detonation in other mediums, they have not been utilized with LSC Figure 10a show s an LSC intersection where an explosive transfer charge powder, typically HNS or PBNX-5, 1 is enclosed in a manifold 32 that assists in transferring detonation These methods do not provide for cutting under the booster or transfer charge but can provide for breaking at that point Additionally, the manifold method is limited in use because the manifold becomes a projectile upon detonation if not retained Therefore, in the case of aircraft transparencv severance, the manifold method is limited to use on the sill of the aircraft, w here it can be retained bv a retainer mounted over the LSC and held to the aircraft's fuselage The retainer is not shown in the intersection figures, but those skilled in the art will recognize that a charge holder can be designed to take account of the LSC intersection or crossover The severance method of the present invention mav be utilized in a system designed so as to be seated proximal to a sill portion of the aircraft and the system may include, in addition to the abov e-descπbed arrangement for freeing a severable region of the canopy, one or more explosiv e charge positioned on or in close to at least a portion of the sill and that ill, on detonation, free substantially the entire transparent portion of the canopy from the aircraft The present system also may be designed so as to selectively initiate either the detonation of the explosiv e charges mounted on or near the sill so as to sever substantially the entire transparent portion of the canopy or the severance of the smaller, severable region of the canopy Detonation of the explosive charges mounted on or near the sill may be preferred over sevenng the severable region of the canopy in situations where the aircraft is on the ground or is otherwise not in flight and immediate egress from the cockpit is necessary. The present severance method may also be designed so that the one or more explosive charges mounted on or near the sill detonate and free a large portion of the canopy from the aircraft simultaneous with the fractuπng of the smaller, severable region to allow egress from the aircraft. Alternately, the present severance method may be used in a system to provide for the detonation of the one or more explosive charges mounted on or near the sill after the fractuπng and sev erance of the smaller, severable region Yanous other details of the design and implementation of aircraft canopy fractuπng systems will be apparent to those of ordinary skill in the art and, therefore, are not provided herein Such details are in part provideα in. for examϋle. "A Svstems Engineeπng Design Guide to Aircraft Explosive Canopy Fractuπng", December 1993. Teledyne Ryan Aeronautical, McCormick Selph Ordinance, the entire content of which is incorporated herein by reference Those of ordinary skill in the art also will appreciate that various changes in the details and arrangements of parts and mateπals w hich have been herein descπbed and illustrated in order to teach tne nature of the invention may be made by those skilled in the art Any such modifications remain within the pπncφle and scope of the invention as expressed in its claims

Claims: WHAT IS CLAIMED IS: 1. A method of seveπng a polycarbonate or laminate of polycarbinate material compπsing: selecting a severance site on said material; surrounding an linear explosive charge in a retainer such that the only area of said explosive charge not surrounded by said retainer faces said mateπal; attaching said retainer to said mateπal at a set distance ("stand off) such that there is open space between said explosive charge and said mateπal such that, upon detonation, said explosive charge generates an explosive cutting face orjet of sufficient strength to sever said mateπal; and detonating said explosive charge. 2 The method of claim 1 wherein said retainer is made of silicone rubber. 3 The method of claim 1 wherein said explosive charge is a linear shaped charge with a V shaped cross section. 4 The method of claim 3 wherein said explosive charge has a metal sheathing of tin. 5. The method of claim 3 wherein said explosive charge has a metal sheathing of lead. 6. The method of claim 3 wherein said retainer and said explosive charge are tooled such that the open end of said V shaped cross section of said explosive charge is at all times parallel to said mateπal. 7 The method of claim 3 wherein said linear shaped charge with a V shaped cross section is placed at a stand off in the range of 0.100 to 0.300 inches. 8 The method of claim 7 wherein said linear shaped charge with a V shaped cross section has a coreload in the range of 12 to 40 grains per foot. 9 The method of claim 7 wherein said polycarbonate or laminate of polycarbonate mateπal is of a thickness on the order of 0.25 +/- 0.15 inches thick; and said linear shaped charge with a V shaped cross section is a PBXN-5 charge with a tin or lead sheathing and a charge on the order of 10 to 15 grams per foot. 10 The method of claim 7 wherein said polycarbonate or laminate of polycarbonate mateπal is of a thickness on the order of 0.50 +/- 0 15 inches thick, and said linear shaped charge with a V shaped cross section is a PBXN-5 charge with a tin or lead sheathing and a charge on the order of 15 to 20 grains per foot. 1 1 The method of claim 7 wherein said polycarbonate or laminate of polycarbonate mateπal is of a thickness on the order of 0 75 +/- 0 15 inches thick and said linear shaped charge ith a V shaped cross section is a PBXN-5 charge with a tin or lead sheatnmg and a charge on the order of 30 to 40 grains per foot 12 A method of seveπng a polycarbonate or laminate of polycarbonate mateπal compπsing affixing a linear shaped explosive charge in proximity to said mateπal whereby in so locating said explosive charge ensuπng that all bends in said explosive charge have a radius of greater than or equal to 2 inches; and detonating said explosive charge 13 A method of seveπng a pattern from a mateπal compπsing * placing a linear shaped explosive charge in proximity to said matenal to be severed about the pattern to be severed from said mateπal such that said explosive charge intersects itself, and detonating said explosive charge 14 The method of claim 13 wherein said explosive charge has a V shaped cross section 15 The method of claim 14 wherein the intersecting portions of said explosive charge with a V shaped cross section are overlaid such that the portion of said explosive charge with a V shaped cross section that runs over top of the other intersecting portion of explosive charge with a V shaped cross section is deformed such that said V shape is flattened to eliminate the cutting force of that section of said explosive charge and instead provides for detonation of said other intersecting portion of explosive charge 16 The method of claim 14 wherein the portion of said explosive charge with a V shaped cross section that is located closest to the mateπal to be severed has a reduced thickness of metal sheathing at the point where the other portion of said explosive charge with a V shaped cross section overlays it 17 The method of claim 14 wherein a solid mateπal is placed between the portion of said explosive charge with a V shaped cross section that is located closest to said mateπal to be severed and said mateπal at the point where the other portion of said explosiv e charge with a \ shaped cross section overlays it 18 A method of detonation transfer betw een intersecting portions of linear snaped explosive charges compπsing placing a booster charge at the point of intersection between said intersecting portions of linear shaped explosive charges, and detonating said linear shaped explosive charges 19 A method of detonation transfer berween intersecting portions of linear shaped explosive charges compπsing. placing an explosive transfer charge at the point of intersection between said intersecting portions of linear shaped explosive charges, enclosing said explosive transfer charge within a manifold, and detonating said linear shaped explosive charges

Inventors: CORONA THEODORE F, HILDEN LYNN G, MENZEL DOUGLAS D, WEISS RAYMOND D, CORONA, THEODORE, F., HILDEN, LYNN, G., MENZEL, DOUGLAS, D., WEISS, RAYMOND, D.
Applicants: CORONA THEODORE F, HILDEN LYNN G, MCCORMICK SELPH INC, MENZEL DOUGLAS D, WEISS RAYMOND D, CORONA, THEODORE, F., HILDEN, LYNN, G., MCCORMICK SELPH, INC., MENZEL, DOUGLAS, D., WEISS, RAYMOND, D.
Application year: 2000
Main classification: B64C
IPC codes: B26F3, B32B27, B64C1